INFECTIOUS DISEASE

A Historical Perspective of Dengue

noreply@blogger.com (A.Hart) — Sun, 15 Nov 2009 05:20:00 +0000

A historical Perspective of Dengue
The story of dengue in many ways starts in the Americas.

Dr. Benjamin Rush made the first good clinical description of dengue.

He was in charge of hospitals under General George Washington in the Oriental Army and described for dengue outbreak in Philadelphia in 1780:

“This fever generally came on with rigor, but seldom with a regularly chilly fit. The pains which accompanied this fever were exquisitely severe in the head, back and limbs.

The pains in the head were sometimes in the back parts of it, and at other times they occupied only the eyeballs.

A few complained of their flesh being sore to the touch, in very part of the body. Its general name among all classes of people was the break-bone fever.”

Dengue today presents with the same fever, headache, eye pain, myalgia and arthralgia.

The US military’s dengue research efforts started just after the Spanish-America War, sparked by the very many dengue causalities in the Philippines.

A dengue commission was established in 1900, and Ashburn and Craig were sent to the Philippines to determine the etiology of dengue and to devise countermeasures.

Although a series of experiments they deduced that dengue was caused by “an ultra microscopic and non-filterable agent,” or a virus.

Ashburn and Craig confirmed that virus could be transmitted from person to person by both mosquito and by syringe; they made careful description of the disease to include leucopenia.

Important for vaccine development, they demonstrated that immunity following infection was absolute; they could only make healthy volunteers with dengue one time.

During World War II, Japan and the United States of America had large dengue research programs.

Dr. Hotta and Dr. Kimura in Japan isolated the dengue serotype 1 virus (DENV-1) shortly before Dr. Sabin and Dr. Schlesinger did so in Hawaii.

In the 1950s, the face of dengue changed dramatically with the widespread recognition of DHF. The army and the Air Force sent Dr. Bill Hammond to investigate the 1956 outbreak of hemorrhagic fever in the Philippines.

He worked with Philippines and Thai scientist to isolate DENV-3 and DENV-4.

The most important pathological process that distinguished DHF from dengue is plasma leakages that can lead to shock and death.

Untreated, DHF has a mortality rate of around 10%. With careful fluid management, however, mortality rates drop to below 1%.

DHF can occur in any age group, but it is most common among children living in dengue hyperendemic areas.
A historical Perspective of Dengue

Anthrax: The Disease and the History

noreply@blogger.com (A.Hart) — Mon, 26 Oct 2009 03:38:00 +0000

Anthrax: The Disease and the History
Anthrax is a peracute, acute or sub-acute disease primarily affecting herbivores but also encountered in other mammals, including humans, and occasionally birds.

The words ‘anthrax’ is derived from the Greek anthrakos, meaning coal, referring o the characteristics eschar in the human cutaneous form of the disease.

The familiar name ‘black bane’ and the French and Italian names for the disease charbon and carbonchio, similarly reflect this manifestation.

Names in other languages and older English names refer to other of its significant manifestations or to its sources of infection, viz Milzbrand (German) and miltvuur (Duth), meaning ‘spleen fire’, pustula maligna (Spanish), Bradford disease, woolsorter’s disease, ragpicker’s disease and so on.
Its numerous synonyms in many national languages and local dialects reflect the historical familiarity with the different syndromes before it was realized that they were manifestations of one etiological agent, Bacillus anthracis.

Fifth and sixth plaques of Egypt in the time of Moses are thought by some to have represented the earliest historical; reports of the anthrax due to respectively to systemic and cutaneous forms of the disease.

Anthrax appears to have featured in Asia Minor at the time of Siege of Troy (ca. 1200 BC) an description of the typical symptoms in the writing of Homer (ca. 1000 BC), Hippocrates (ca. 400 BC), Varro (116 – 27 BC), Virgil (70 – 19 BC and Galen (ca. 200 AD) indicate that the Greeks and Romans were well acquainted with it.

Scientifically reports began with the descriptions of malignant pustule and the disease in animals in 1700s.

The nineteenth century saw anthrax as the first disease of man and animals shown to be caused by a microorganism and as the disease on which much of the original work on bacteria and vaccines was done.
Anthrax: The Disease and the History

Measles

noreply@blogger.com (A.Hart) — Mon, 05 Oct 2009 02:41:00 +0000

Measles
Measles is a viral disease most commonly affecting school age children, although adults contact the ease as well.

There are two main varieties: German measles and common measles.

There is an immunization but if there are existing conditions, they may be complications.

German measles (rubella) is caused by a virus and has a rapid recovery period, but the disease must run its course and there is little that can be done medically for its treatment, German measles is a mild illness, alarming only to pregnant women.

If a woman contracts German measles during the early months of pregnancy the newborn can suffer from such malformations as heart defect, deafness, mental retardation, and blindness.

Symptoms of German measles may include fever headache and stiff joints (mainly in the neck), although most people seldom complain of any symptoms.

A rash that lasts for about three days appears on the arms, chest and forehead.

Lotion may be applied to the rash to relieve itching, and the patient should stay away from other people to avoid spreading the disease.

Common measles (rubeola) is a highly contagious disease spread by droplets from the nose throat and mouth.

The first symptoms of common measles are a fever that lasts for a couple of days followed by a cough, runny nose and inflammation of the eyes.

Stomach pains, diarrhea, and vomiting may also occur. Within twenty forty-eight hours, small red spots with white centers appear in the inside of the cheeks.

A rash which is first seen on the face and upper neck and then spreads down the back and trunk and then to the limbs, usually appears three to five days after the onset of the first symptoms.

As the rash spreads fever goes down. After about five days, the rash fades in the same order it appeared. Common measles may have been serious complications, such as ear infections, pneumonia, encephalitis and injury to the nervous system.
Measles

American Trypanosomiasis

noreply@blogger.com (A.Hart) — Sun, 13 Sep 2009 01:57:00 +0000

American Trypanosomiasis
American Trypanosomiasis or Chaga’s disease is caused by Trypanosomiasis cruzi, a protozoan parasite found only in the America; infects wild animals and to a lesser extent humans from southern South America to the southern United States.

An estimated 10-12 million people are infected, mostly in rural areas, resulting in about 45,000 deaths annually.

The disease is often acquired in childhood. In many countries in South America, Chaga’s disease is the most important cause of heart disease.

T. cruzi, is transmitted by reduviid (triatomine) bugs infected by ingesting blood from animals or humans who have circulating trypanosomes.

Multiplication occurs in the ingesting tract of the bug and infective forms are eliminated in feces.

Infection in humans occurs when the parasite penetrates the skin through the bite wound mucous membranes or the conjunctiva.

Transmission can also occur by blood transfusion or in utero. From the blood stream, T. cruzi invades many cell types but has a prediction for myocardium, smooth muscle and CNS glial cells.

Multiplication causes cellular destruction, inflammation, and fibrosis with progressive disease over decades.

Symptoms
The acute stage is seen principally in children and last 1-months. The earliest findings are at the site of inoculation either in the eye – Romana’s sign (unilateral edema, conjunctivitis and lymphadenopathy) – or ion the skin or a chagoma (selling with the local lymphadenopathy).

Subsequent findings include fever, malaise, headache, mild hepatosplenomegaly, and generalized lymphadenopathy.

Acute myocarditis and meningoencephalitis are rare but can be fatal.
American Trypanosomiasis

Vibrio Cholerae and Cholera

noreply@blogger.com (A.Hart) — Sun, 30 Aug 2009 07:17:00 +0000

Vibrio Cholerae and Cholera
The bacterium V.cholerae is a gram negative, nonsporulating, straight or curved rod. It possesses a single polar sheathed flagellum and is highly motile.

A halophiclic organism, it is found in estuarine or marine environments, and it is growth in laboratory media is generally stimulated by the presence of 5 to 90 mM sodium, depending on actual culture conditions.

Outside the human host, Vibrio Cholerae has been found free living in water and also in association with plankton, most notably copepods.

In its most severe form, cholera is capable of causing death within 3 hr after the onset of symptoms, which occurs 12 to 72 hrs after ingestion of V. Cholerae.

The distinctive feature of the disease is the profuse secretory diarrhea that results from the action of cholera toxin on cells of the intestinal epithelium.

Fluid loss by this route can reach as much as 200 ml/kg of body weight per day with total losses exceeding 100% of body weight over the course of several days.

The concomitant loss of plasma solutes such as sodium potassium and chloride ions leads to electrolyte imbalances, acidosis and ultimately death.

However, effective treatment of cholera is both simple and relatively inexpensive, consisting of oral and/or intravenous rehydration therapy couples with administration of antibiotics.

Cholera typically begins with the ingestion of V. Cholerae in contaminated food or water.

Cholera is a non invasive infection where the organism colonizes the intestinal lumen and produces a potent enterotoxin.

In severe cases, the hypersecretion of sodium, potassium, chloride and bicarbonate induced by the enterotoxin results in a profuse, pale, watery, diarrhea containing flakes of mucus, described as rice water stools.

Unless the massive losses of fluid ad electrolyte are replaced, there is a fall in blood volume and pressure, an increase in blood viscosity. Renal failure, and circulatory collapse.

In fatal cases death occurs within a few days.
Vibrio Cholerae and Cholera

Nipah Virus

noreply@blogger.com (A.Hart) — Fri, 24 Jul 2009 00:27:00 +0000

Nipah Virus
In 1998, Nipah virus first emerged in Malaysian pigs as a respiratory and neurology disease and then jumped to humans with lethal consequences.

Nipah virus can cause severe encephalitis and vascular disease in people, and in the Malaysia outbreak, those with virus infections had a mortality of about 40 percent.

More than 100 people died.

Essentially all of those who became infected had direct contact with pigs, either in pig-rearing facilities or in slaughter houses.

The rapid spread of Nipah virus among pig farms throughout peninsular Malaysia and into Singapore was more likely caused by an intense sell-off of infected pigs following the initial outbreak.

In order to control outbreak, millions of pigs were slaughtered, hundreds of farms were closed, and tens thousands of jobs lost Nipah virus cost the Malaysia government more than $350 million and destroyed the live-hoods of countless numbers of people.

The origin of Nipah virus has been traced back to two native species of fruit bats or “flying foxes” from the genus Pteropus (and the family Pteropodidae) the Malayan Flying Fox – Pteropus vampyrus, which is ubiquitous through peninsular Malaysia, Borneo, and Thailand, and the Variable Flying Fix – P. hypomelanus.

Pteroped bats, which do not develop clinical signs of disease when infected with Nipah virus are considered the natural reservoir for henipaviruses the vital genus to which Nipah belongs) and have most likely co-evolved with these viruses over time.

The range includes the Old World typical regions, from Madagascar eastward through Southeast Asia, Australia and the South Pacific Island.

The bats serve vital roles in tropical ecosystems acting as seed disperses and pollinators for rainforest plants.

Hunting and deforestation threaten this ecologically important group of animals throughout their range.
Nipah Virus

The 1976 Swine Flu Fiasco

noreply@blogger.com (A.Hart) — Tue, 16 Jun 2009 02:38:00 +0000

The 1976 Swine Flu Fiasco
Shortly after new army recruit and soldiers returning form the Christmas holidays arrived at Fort Dix, New Jersey, in January 1976, an outbreak of influenza ensued.

Most of the illness remained mild with only a few hospitalized victims. One sick recruit refuse to answer sick call died from influenza related pneumonia.

Tests showed that he and three others had been infected with and H1N1 swine virus, while all the others had been infected with a variant of the H3N2 virus hat had been circulating every year since it was introduced to human population in 1968.

There had been a few reported cases of human infection by the swine flu since 1974, but the virus had grown so adapted to pigs that it no longer adjusts well enough in the human host to be transmitted from person to person.

Fearful that the H1N1 subtype of 1918 had begun to resurface within the human population, with the prospect of a similar pandemic, scientist debated the issue and considered what should be done to prevent such a disaster.

Some scientists believed this was not the same type variant of 1918, while many others feared it could be.

President Ford at that time, following recommendations coming out of the debate announced in March the federal government’s intent to immunize the entire population of the United States against the swine flu to prevent a disastrous outbreak expected in the fall of 1976, similar to the 1918 pandemic.

Congress appropriated $135 million for the vaccination program.

Ten days after the vaccinations began, three elderly individuals with the heart conditions died shortly after receiving their shots. The news media jumped on this to create fear of the vaccine.

This prompted President Ford and his family to encourage people to take the shots by televising their own vaccinations.

Over 40 million people did receive the vaccine before the program ended in December.
The 1976 Swine Flu Fiasco

H1N1 Swine Influenza Virus

noreply@blogger.com (A.Hart) — Tue, 26 May 2009 23:54:00 +0000

H1N1 Swine Influenza Virus
Viruses of the classical H1N1 lineage were the dominant cause of influenza among pigs in North America from their first isolation.

Classical H1N1 viruses have also been isolated from pigs in South America, Europe and Asia.

There is only limited evidence of maintenance of human H1N1 influenza viruses after natural introduction into swine populations but human H3N2 viruses have been recovered frequently from pigs in Asia and Europe.

Experimental infection studies have shown that pigs can be infected with a wide range of avian influenza virus (AIVs) and naturally acquired infections of pigs with AIVs have also been documented from multiple areas of the world.

In particular, an avian H1N1 virus introduction into pigs Europe in late 1970s spread throughput much of the European continent and United Kingdom and ultimately became a dominant cause of swine flu in these areas.

These avian-like H1N1 viruses have also undergone genetic/antigenic drift and have spread from pigs to domestic turkeys.

The occurrence of influenza virus infections in pigs poses two important public health issues: zoonotic infections of people with swine influenza viruses and the potential for pigs to serve as hosts for the creation of novel viruses of pandemic potential for the human population.

Infections with swine influenza viruses is generally limited to the respiratory tract, with virus replication demonstrated in epithelial cells of the nasal mucosa, tonsils, trachea, lungs and tracheobronchial lymph nodes.

Swine flu is an acute infections and virus clearance is extremely rapid. In most experimental studies, nasal virus shedding begins on day 1 postinoculation (P1) and ceases within 7 days.

Likewise, swine influenza virus could not be isolated from lungs or other respiratory tract tissues after day 7.

Infections with H1N1, H1N2 and H3N2 subtype viruses are clinically similar, and viruses of all subtypes have been associated with acute respiratory episodes in most European countries.

Disease onset is sudden, after an incubation period of 1 – 3 days. Disease signs typically appear in a large percentage of animals of all ages within a herd or epidemiological unit.
H1N1 Swine Influenza Virus

Influenza – Major Occasional Pandemic Outbreaks

noreply@blogger.com (A.Hart) — Mon, 27 Apr 2009 07:06:00 +0000

Influenza – Major Occasional Pandemic Outbreaks
Influenza or simply “flu” is caused by a virus. It occurs not only in occasionally major pandemic outbreaks, but also in epidemics of variable severity almost every winter.

The term “influenza” has been derived from the Italian ‘influentia’ in the mid-1300s, indicating that, at the time, the illness was believed to result from astrological influences.

Yet, the aetiloogy of the disease and the explanation for its peculiar behavior remained elusive.

At the turn of the 19th century, influenza was thought to be due to a bacteria infection with Haemophilus influenzae.

It was not until 1931 that Richard Shope showed that swine influenza could be transmitted with filtered mucus, indicating that the causative agent was a virus.

A few years later, Smith and co-workers isolated the influenza virus from humans with respiratory illness.

The burden of influenza for the society, not only from a clinical but also from an economic perspective, is often underestimated.

This relates particularly to the recurring annual winter epidemics. Fortunately, since the virus was first discovered, efficient means to contain the infection have been developed.

Vaccination is the cornerstone of influenza prevention and control. Accordingly, the WHO (World Health Organization) has issued guidelines for implementation of influenza vaccination programs in individual countries.

Yet, in many places, implementation of vaccination programs remains woefully deficient. This implies that significant numbers of people at risk of the complications of influenza remain vulnerable to infection and possibly death.
Influenza – Major Occasional Pandemic Outbreaks

Pathogen

noreply@blogger.com (A.Hart) — Mon, 13 Apr 2009 07:14:00 +0000

Pathogen
A pathogen is defined as any organism capable of invading the body and causing disease.

Such an organism is said to be pathogenic.

Koch isolated and identified organisms such as Mycobacterium tuberculosis and Bacillus anthracis, where the isolation of the organism only occurred in the presence of disease.

It is to define these bacteria as pathogens.

They also fulfill Koch’s further definition of a pathogen that introduction of a pure culture of the organism into the healthy host can cause the disease.

This definition works well for many bacteria, but does nor fully describes the complex interactions between microbes and humans which more recent understanding has revealed.

For instance, Escherichia coli is found in huge numbers in the healthy human bowel, and could therefore be defined as non-pathogenic.

E. coli is also important cause of diarrhoeal disease and potent enterotoxins and other pathogenic determinants have been described in some strains.

E. coli can therefore behave as a pathogen or as a colonizer depending on various circumstances.

A broader definition of a ‘biological agent’ used in European Union legislation is: ‘any microorganism, cell culture or toxin capable of entering the human body and causing harm’.

Changes in medical practice mean that increasing numbers of patients are immunocompromised as the result of either disease or treatments.

In such patients organisms which are usually non-pathogenic, such as saprophytic fungi, may act as pathogens.

Intensive therapy medicine, with insertion of intravascular cannulae, allows Staphylococcus epidermitis, a normal part of the skin flora, to enter the cannula and cause blood-borne infection: behaving as a pathogen.
Pathogen

History of Influenza

noreply@blogger.com (A.Hart) — Tue, 24 Mar 2009 01:13:00 +0000

History of Influenza
Hippocrates recorded an epidemic of a flu-like infection in 412 B.C that wiped out the Athenian army.

The sixteenth century saw two flu pandemics that spread throughout Europe. The first, in 1510, infected nearly the entire population of Europe, but claimed few lives.

The second, in 1580, devastated cities and spread through the whole of Western Europe. The city of Rome, for example, had 9,000 fatalities.

At least pandemics of flu spread throughout Europe in the seventeenth century. In the past of 200 years eight great flu pandemics seized the world prior to the devastation wrought by the 1918 flu.

During a period of fourteen months beginning in the spring of 1918, half of the entire world’s population was infected with the influenza virus and nearly 41 million people died.

Every country in the world was affected, no matter how remote, and this occurred in an era before air travel and a global community existed.

Victims who died during the 1918 flu were typically healthy young adults. Among the 20 to 40 year old age group, the fatality rate from the 1918 flu was 50 percent.

The virus of 1918 was so effective at killing its host that within a short period of time it rendered itself extinct, people either immune to the virus or dead.

Since that time several other lesser pandemics have occurred across the globe, but health officials anxiously await the next deadly flu pandemic, which they predict as inevitable.

When it occurs, experts foresee millions of death, hospitals quickly flooded with cases of pneumonia, and every health care system in the world over whelmed by the volume of flu victims.
History of Influenza

Malaria in Ancient Greece and Rome

noreply@blogger.com (A.Hart) — Wed, 04 Mar 2009 18:37:00 +0000

Malaria in Ancient Greece and Rome
The ancient Greeks were well acquainted with malaria from about the year 500 BC when infected slaves may have carried the disease into Greece.

To a certain extend, malaria may well have contributed to the breakdown of ancient Greek civilization.

As early as 46 BC, Hippocrates described the malaria symptoms and differentiated between its various forms.

However, he incorrectly assumed that malaria was caused as a result of drinking stagnant water.

Malaria did not discriminate when choosing its victims. One famous victim was Alexander the Great.

Ancient Rome was seen to be vulnerable to the fever to the extent that Gei Febris, the fever goddess, as worshipped for her ability to cure the disease.

The fall of Rome has been attributed not only to hedonism and decadence, but also to the debilitating effects of the illness on its citizens.

Three emperors, Hadrian, Vespasian and Titus, are believed to have succumbed to malaria, while St Augustine is thought to have contracted it while carrying Christianity’s message from Rome to Britain.

Medieval Europe was well acquainted with malaria until land reclamation and improved drainage disrupted the mosquitoes’ breeding habits.

These habits were further discouraged inadvertently by the increased building of well lit and ventilated houses.
Malaria in Ancient Greece and Rome

The word of Influenza

noreply@blogger.com (A.Hart) — Mon, 09 Feb 2009 13:14:00 +0000

The word of Influenza
The word influenza is Italian for influence, as in the astral or occult influence of a visitation or outbreak that affects many people at the same time. First used in 1504, the word signified any disease epidemics.

In a severe flu outbreak of 1743 the word influenza was applied to the epidemic that began in Italy and spread throughout Europe.

Since then, the influenza, shortened to flu, means a serious infectious disease characterized by muscle and joint aching, prostration, and respiratory congestion with fever and headache.

It was not until 1931 that an influenza virus was identified in pigs, and finally in 1933 a human influenza virus was discovered by three researchers: Smith, Andrewes, and Laidlaw.

Both of these viruses were closely related to the Spanish flu virus of 1918. During the time of the 1918 flu pandemic, however, the suspected culprit was a bacterium named Hemophilus influenza. Viruses had not yet been discovered.

Although most people consider the flu simply and annoyance, and possibly a danger to seniors in poor health, influenza has been responsible for repeated, devastating worldwide pandemics capable of bringing entire nations to their knees.

It is hard to imagine today, but in 1918 the entire world was in the clutches of a deadly flu virus. The 1918 flu still remains the greatest plague the world has ever seen.
The word of Influenza

Pertussis

noreply@blogger.com (A.Hart) — Mon, 19 Jan 2009 01:35:00 +0000

Pertussis
Also known as whooping cough, pertussis is a respiratory disease caused by the bacterium Bordetella pertussis. The introduction of the whole-cell vaccines in the middle of the last century resulted in dramatic decrease in disease incidence.

The virulence factors of Bordetella pertussis can be divided into adhesions, such as pertactin and toxins, such as pertussis toxin. Adhesins attachment to the host and toxins are involved in immune evasion and possible resource extraction.

The infection is characterized by bacterial colonization of ciliated respiratory in the trachea and bronchi. The incubation period is 6 – 20 days.

Classical pertussis is an illness of three stages. It starts with a catarrhal stage, with nonspecific symptoms similar to those of the common cold (duration 1 to 2 weeks). At the paroxysmal stage (duration 2 to 6 weeks), the cough becomes more prominent with staccato attacks, postussive whooping, and vomiting.

At the convalescent stage (duration several weeks), the frequency and severity of coughing attacks gradually decrease. The most severe cases of whooping cough occur in unvaccinated children under 1 year of age. This group accounts for most deaths.

Whooping cough is presently one of the 10 most common causes of death from infectious disease. The WHO estimates it to cause 50 million illnesses and over 350,000m deaths worldwide each year.

After introduction of whole-cell vaccines in the 1950s, its morbidity and mortality were significantly reduced in the developed world, whereas in the developing countries whooping cough has remained a major cause of infant mortality.

In highly vaccinated communities, Bordetella pertussis and Bordetella parapertussis infections often go undiagnosed because pertussis is thought to be rare and adequate laboratory diagnostic tests are not used or available.
Pertussis

Mumps (Epidemic Parotitis)

noreply@blogger.com (A.Hart) — Sat, 03 Jan 2009 23:45:00 +0000

Mumps (Epidemic Parotitis)
Mumps was recognized as a distinct clinical entity by the ancients. In ‘Of the Epidemics’, Hippocrates described mumps as follows: ‘Swellings appeared about the ears in many on either side, and in the greatest number on both sides…. inflammations with pains seized sometimes one of the testicles, and sometimes both.’

Mumps was not considered a serious disease, although surprisingly large literature has appeared on the subject.

Contrary to measles, varicella, and pertussis, mumps is not a highly contagious disease, rarely afflicting infants. The majority of cases occur between five and ten years of age and 30 to 40 percent of the cases have inapparent infections.

Complications include testicular swelling and encephalitis, usually not succeeded by any residuals. Contrary to belief, mumps is rarely a cause of male sterility.

Because mumps is not a highly contagious disease, many children escape infection. Under certain circumstances epidemics of the disease occur among adults.
Mumps (Epidemic Parotitis)

Symptoms of measles

noreply@blogger.com (A.Hart) — Mon, 22 Dec 2008 14:37:00 +0000

Symptoms of measles
About ten to fourteen days after exposure to the measles virus, people infected with measles will get a rash, high fever cough, runny nose, and watery eyes. The eye symptoms can develop into conjunctivitis (pink eye), a condition that causes swelling and redness of the eye, tearing, and sensitivity to light. The skin rash often takes the form of bright red spots that are distinct and separate from each other.

They may multiply so rapidly, however that they appear to be a solid red mass. The rash usually starts behind the ears and along the hairline and then quickly spreads to the rest of the face, moving downward to the rest of the body. In addition to this red rash, light spots resembling grains of salt may appear on the inside of the patient’s cheeks near the back of the mouth. Doctors call these Koplik’s spots. These typical measles symptoms last for one to two weeks.

Most people recover form measles within ten to fourteen days. After they are well again they are no longer contagious, which means they no longer infect other people with the disease. In addition, people who have had measles develop an immunity to it – they will never catch measles again, even if someone with the disease sneezes or coughs right in their face.
Symptoms of measles

Measles

noreply@blogger.com (A.Hart) — Wed, 17 Dec 2008 14:35:00 +0000

Measles
Measles is a highly contagious disease. It is caused by a virus – an extremely tiny organism that can only reproduce itself by residing within living cells. Humans are the only living creatures who can develop measles, and they can only get it if they are exposed to the measles virus.

The most common way that people get infected with the disease is by breathing in tiny droplets of water vapor containing the measles virus. An uninfected person can get measles just by breathing the air in a room that was previously occupied by an infected person. The measles can live in the air for two hours after an infected person leaves the room. People can also get measles if they have direct contact with fluid from the nose or mouth of an infected person.

Once introduced into a person’s respiratory system, the measles virus proceeds to attach itself to the lining of the airways. Drawing energy from this new host, the virus begins to multiply and spread through the body.
Measles

Filariasis

noreply@blogger.com (A.Hart) — Thu, 04 Dec 2008 16:00:00 +0000

Filariasis
Filariasis is a helminthic infection found principally in tropical and subtropical areas in Africa, and in the South Pacific regions. The disease is transmitted from man through several genera and species of mosquitoes. The acute disease is manifested by recurrent chills and fever and by visible swelling or nodules of the lymphatics and redness of the overlaying skin due to parasitic involvement.

The illness usually subsides gradually with or without therapy. But in those who have been repeatedly infected and are chronically ill, the inflammatory reaction and scarring of the tissues surrounding the vessels may impede the flow of lymph and blood, and mammoth enlargement (“elephantiasis”) of the arms, legs, scrotum and breasts can occur. During World War II approximately fifteen thousand American military personnel became infected, but prompted withdrawal of these patients from the endemic zones prevented chronic disease and elephantiasis.

Filariasis was the first human disease described in which transmission through the skin was cause by the bites of arthropods. Doctor O. Wucherer (1868) found the embryonic filarial worms in the urine of a patient in Bahia, Brazil. T. R. Lewis (1872), working in India, observed the embryos in the urine and also in the blood, and Joseph Bancroft (1878) in Brisbane, Australia first described the adult worm. The parasite has been designated Wuchereria bancrofti.

The momentous discovery of the role of the mosquito in transmitting the disease was made by the Scotsman Patrick Mansion (1877) while he was practicing medicine in the Far East with the Chinese Imperial Maritime Customs. He became interested in the disease that confronted him, including filariasis. In that disease he recognized the parasites in peripheral blood films and also in postmortems material.

He noted the nocturnal appearance of the parasites in the peripheral blood and postulated that a blood sucking insect might be responsible for transmitting the infection. Manson proved the presence of the microfilaria in the mosquito Culex fatigans, thus supplying the missing link in the life cycle of the disease.
Filariasis

Giardiasis

noreply@blogger.com (A.Hart) — Wed, 12 Nov 2008 05:45:00 +0000

Giardiasis
Giardiasis is the most common intestinal protozoal infection in children in the United States and in most of the world. It is caused by Giardia lamblia. Endemic worldwide, the infection is classically associated with drinking contaminated water, either in rural areas or in areas with faulty purification systems. But even ostensibly clean urban area water supplies can be contaminated intermittently.

Persons have acquired the infection in swimming pools. Fecal oral contamination allows person-to-person spread. Day care centers have been recognized as major sources of infection, with an incidence of up to 50% reported in some centers. No symptoms occur in 25% of infected persons, facilitating spread to household contacts. Food-borne outbreaks also occur. Although infection is rare in neonates, giardiasis may occur at any age.

Symptoms
Giardia infection is followed by asymptomatic cyst passage, acute self-limited diarrhea, or a chronic syndrome of diarrhea, malabsorption and weight loss. Acute diarrhea occurs 1-2 weeks after infection and is characterized by abrupt onset of diarrhea with greasy, malodorous stools; malaise; flatulence; bloating; and nausea. Fever and vomiting occur in a minority of patients. Urticaria, reactive arthritis, biliary tract disease, gastric infection and constipation have occasionally been reported.

The disease has protracted course (more than 1 week) and frequently leads to weight loss. Patients who develop chronic complain of profound malaise, lassitude, headache, and diffuse abdominal pain in association with bouts of diarrhea – most typically foul smelling, greasy stools – intercalated with periods of constipation or normal bowel habits. This syndrome can persist for months until specific therapy is administered or until is subsides spontaneously. Chronic diarrhea frequently leads to malabsorption, steatorrhea, vitamin A and vitamin B12 deficiencies, and disaccharides depletion. Lactose intolerance, which develops in 20 – 40% of patients, can persist for several weeks after treatment and needs to be differentiated from relapsing giardiasis or reinfection.
Giardiasis

Malaria - Infectious disease

noreply@blogger.com (A.Hart) — Sat, 08 Nov 2008 02:29:00 +0000

Malaria - Infectious disease
Malaria kills three people every minute. Each year, it is thought that as many as 2.7 million people die from malaria and between 300 and 500 million suffer potentially fatal cases. The disease threatens 2.5 billion people, almost half the world’s population.

African countries south of the Sahara desert account for 90% of all clinical cases and nearly 90% of deaths caused by malaria. Children are most vulnerable to this major killer. In rural, tropical African areas, one child in 20 dies from malaria before he or she reaches the age of five years.

What is Malaria?
Malaria is a disease, caused by any of four species of parasite that is carried from person to person by a mosquito and transmitted by the bite of an infected female Anopheles mosquito.

Malaria is primarily a disease of the blood cells and small blood vessels. By causing the cells to become ‘sticky’ and eventually to burst, it causes blockages of the small blood vessels in the major organs of the body. This can cause severe disease and death – in case of the infection with the P. falciparum species of malaria, this can occur within 24 hrs of the disease first becoming evident.

Malaria caused by the other three parasite, namely Plasmodium vivax, P. ovale and P. malariae, is much milder and does not cause death, although they cause recurrent malaria than in itself is a debilitating disease.

The malaria parasite is found mostly in the tropical and subtropical regions of the world. Mosquito breeding is severely hampered in temperatures below 20 degree C. Optimal conditions for breeding are at temperatures around 30 degree C together with humidity levels of over 60%. Consequently, temperature and humidity largely dictate whether a country is likely to experience year-round malaria, seasonal malaria or localized break through.

The severity of malaria and its incidence is governed also by the immunity levels of the host, man. Immunity depends on constant exposure to the malaria-infected mosquito. Hence war and civil disturbances leading to an influx of non-immune workers, as well as tourism, all lead to the exposure of non immune to the malaria parasite.
Malaria - Infectious disease

Infectious Disease - Rabies

noreply@blogger.com (A.Hart) — Sun, 26 Oct 2008 01:08:00 +0000

Infectious Disease - Rabies
At the end of the nineteenth century, hundreds of people died from rabies every year. Almost invariably, these people got the disease from the bite of a domestic animal, usually a dog.

Because of the efforts of Louis Pasteur and many others, it is rare today for some one to die from rabies. And the few cases of rabies that arise each year almost invariably come about as a result of a bite from a wild animal, like a skunk or a bat. The rarity of the disease and the elimination of rabies from domestic animals are due largely to Pasteur’s discoveries and intense vaccination programs.

But rabies remains as a glaring example of the pain and suffering that can follow infection. And rabies is only one example of thousands of infectious diseases – diseases caused by prions, viruses, bacteria, fungi, and parasites – that make us sick and kill us. Some infectious may be essential. Others are terrifying.

A rhabdovirus virus causes rabies. There are many different types of rhabdoviruses and they cause a whole range of disease – rabies is one of the worst. The rabies is bullet shaped, covered with a large sheet of host-cell membrane and fortunately for all of us, is easily destroyed by soaps or drying. Rabies viruses are about 75 nm (nanometers) in diameter and about 150 to 300 nm long. A nanometer is one billionth of a meter, far beyond the realm human vision. These are tiny packets of trouble.

Rabid animals transmit rabies in their saliva. From the bite wound, the virus makes its way into neurons. Then it travels along the neurons to the central nervous system (brain and spinal cord) where it sets up shop. In the central nervous system, the rabies virus begins to destroy neurons as it produces more virus. Some of the new virus particles travel to the salivary gland, where they help spread the disease to others through bites.

In the process of its self-replication, the rabies virus decimates many of the neurons in the central nervous system. The result is a mental meltdown. But the virus doesn’t destroy all of the brain – just enough to drive the dog mad, just enough to make dog want to bite every other living thing it sees and pass on the infection.
Infectious Disease - Rabies

Escherichia coli

noreply@blogger.com (A.Hart) — Sun, 21 Sep 2008 23:16:00 +0000

Escherichia coli
Animal and human feces and untreated water are the source of Escherichia coli contamination in food. Any food product (meat, vegetables, and dry products) can become contaminated. There are 4 virulent strains of Escherichia coli; 3 of them 4 virulent strains cause mild diarrhea, cramps and fluid loss.

E.coli 0157:H7, the fourth and most virulent strain, is of current concern because of its effect: bloody diarrhea, severe abdominal pain and cramps. Hemolytic uremic syndrome, a possible complication of this illness, is the leading cause of kidney failure in children. In the past few years, under cooked ground beef products have been implicated in transference of E.coli 0157:H7.

There is estimated annual incidence of over 200,000 cases of enteric E.coli in the United States with about 400 fatalities.

The temperature range for growth of E.coli is 36 degree F to 114 degree F. E.coli are less resistant to heat than are Salmonella spp. Heating foods to temperatures that destroy Salmonella are sufficient to inactivate any E.coli which may be present.

Some critical problems which are responsible for illnesses cause by E.coli include

Animal feedlot practices which allow some animals to become colonized

The spreading of the organisms during slaughtering, processing, food preparation, and poor personal hygiene

Improper sewage treatment and disposal; use of improperly treated animal and human waste to fertilize crops

Allowing food products to remain above 36 degree F which enables this microorganism to multiply during distribution and service

Infected people who contaminate food products because they do not washed their hands and fingertips correctly after using the toilets

Escherichia coli

Food System that Lead to Salmonellosis

noreply@blogger.com (A.Hart) — Sat, 13 Sep 2008 01:47:00 +0000

Food System that Lead to Salmonellosis

The government sets no microbial standards or pasteurization specifications that can be used to control the presence of this microorganism in raw food in retail food operations, Meat animals and poultry are often infected as a result of the environment in which they are slaughtered. Since they often appear to be disease free, they contaminate other carcasses through cross contamination during slaughtering procedures. Salmonella are present at low levels within the yolks of eggs produced by diseased flocks of chickens. They are found in fish and seafood taken from contaminated water.

During transport and distribution, are often above 41 degree F allowing Salmonella to multiply in food products.

Food may not be heated sufficiently to destroy Salmonella. Cooks can only guess when food is cooked adequately. Hence, Salmonella spp. survive to cause illness.

There is post cooking cross contamination of cooked food when it is cut on contaminated cutting boards or with knives used to prepare raw products contaminated with Salmonella.

In spite of regulations forbidding people to work when they are ill, people who are ill or carries of Salmonella spp. continue to work in food operations. These individuals shed the microorganism in their feces and spread Salmonella to the food they prepared or touch. This occurs when they do not properly washed their fingertips and under their fingernails after defecating.

Food System that Lead to Salmonellosis

Salmonella spp.

noreply@blogger.com (A.Hart) — Tue, 02 Sep 2008 02:46:00 +0000

Salmonella spp.
There are over 2000 types of Salmonella, all are pathogenic to humans. This microorganism is often found in raw poultry products and may also be present on other raw meat products. It can be transmitted to other food products by cross contamination, improper food handling and poor sanitation.

Symptoms of illness include abdominal cramps, diarrhea, fever, and chills. The illness develops 8 to 72 hours after ingestion of food containing the microorganisms. Ingestion of greater than 10,000 Salmonella cells in a meal is usually necessary to cause illness in healthy people. However, as few as 4 to 5 cells per 100 grams of food can cause illness when present in foods containing higher amounts of fats such as cheese and chocolate candy. Fat in these foods provides a protective barrier around the microbial cells and prevents their disintegration by stomach acid during digestion.

Severe complications form salmonellosis include: reactive arthritis, cardiac inflammation, intracranial, and other nervous system involvement and osteomyelitis. Because of the seriousness of illness caused by Salmonella, the standard for heat destruction times and temperature for this pathogen are used as a basis for food pasteurization.

Recent news about Salmonella;
In June 2006, the BBC reported that the Cadbury chocolate manufacturer withdrew a number of products when products contaminated with salmonella caused up to 56 cases of Salmonellosis.

In February 2007, the U.S. FDA issued a warning to consumers not to eat certain jars of Peter Pan peanut butter or Great Value peanut butter due to risk of contamination with 'Salmonella Tennessee'.

July 2008, the U.S. Food and Drug Administration suspects that the contaminated food product is a common ingredient in fresh salsa, such as raw tomato, fresh jalapeño pepper, fresh serrano pepper, and fresh cilantro. It is the largest reported salmonellosis outbreak in the United States since 1985.
Salmonella spp.

Campylobacter jejuni

noreply@blogger.com (A.Hart) — Tue, 29 Jul 2008 03:38:00 +0000

Campylobacter jejuni
Campylobacter jejuni is considered to be a pathogen principally of veterinary significance only slightly more than decade ago, Campylobacter jejuni (formerly known as Vibrio fetus) was known to cause abortion in sheep. Following the development of procedures for detecting the organism in stool specimens, Campylobacter jejuni became recognized as a leading cause of acute bacterial gastroenteritis in humans.

Campylobacter jejuni is a gram-negative, microaerophilic, thermophilic rod that grows best at 42°C (107°F) and low oxygen concentrations. These characteristics are adaptations for growth in its normal habitat – the intestines of warm-blooded birds and mammals. Several closely related species with similar characteristics, C. coli, C. fetus, and C. upsalienis, may also cause disease in man but are responsible for less than one percent of human infections annually.

Evidence suggests that Campylobacter is responsible for at least as many cases of enteric illness as Salmonella. Indeed, it is now believed that campylobacteriosis is more common in the United States than salmonellosis and shigellosis combined. Common symptoms of campylobacter enteritis include profuse diarrhea (sometimes containing blood), abdominal cramps and nausea. Human volunteer and retrospective studies of food associated outbreaks revealed that ingesting relatively small numbers (only a few hundreds cells) of Campylobacter jejuni can produce illness.
Campylobacter jejuni