Poliovirus: Transmission, Effects, and Global Eradication Efforts

Poliovirus, the causative agent of poliomyelitis (polio), is a highly infectious virus that primarily affects young children. Belonging to the Enterovirus genus within the Picornaviridae family, poliovirus is composed of an RNA genome encased in a protein capsid. There are three serotypes of poliovirus: type 1, type 2, and type 3, each capable of causing disease. These serotypes exhibit varying degrees of pathogenicity, with type 1 being the most prevalent globally and often associated with the most severe outbreaks.

Transmission of poliovirus occurs through the fecal-oral route, often via contaminated water or food. This mode of transmission highlights the importance of sanitation and hygiene in controlling the spread of the virus. Once ingested, the virus multiplies in the intestine, leading to the release of viral particles into the environment, where they can infect others. In some cases, the virus can invade the bloodstream and subsequently target the nervous system, leading to paralysis in severe cases. Most infections are asymptomatic or result in mild, flu-like symptoms, but a small percentage of cases progress to paralytic polio, which can cause permanent disability or death. This severe manifestation of the disease underscores the urgency of vaccination efforts.

The global fight against polio has seen significant progress since the launch of the Global Polio Eradication Initiative in 1988. Through widespread vaccination efforts, the incidence of polio has decreased by over 99%, with wild poliovirus now endemic in only a few countries, such as Afghanistan and Pakistan. The oral polio vaccine (OPV) and inactivated polio vaccine (IPV) have been instrumental in this success, providing immunity and preventing transmission. OPV is particularly effective in community-wide immunization campaigns, while IPV is used in developed countries to ensure individual immunity.

Despite these achievements, challenges remain, including vaccine-derived poliovirus outbreaks, which occur when the weakened strain in the OPV mutates and regains virulence. There is also a pressing need for continued immunization to prevent resurgence. Ongoing efforts focus on maintaining high vaccination coverage, conducting surveillance to quickly identify cases, and improving sanitation and hygiene practices to achieve the goal of complete eradication. The fight against poliovirus is a critical public health initiative, emphasizing the need for global collaboration and commitment to protect future generations from this debilitating disease.
Poliovirus: Transmission, Effects, and Global Eradication Efforts

Hepatitis B transmission

Hepatitis B is a viral infection that attacks the liver and can cause both acute and chronic disease. It is caused by the hepatitis B virus (HBV) and can cause acute and chronic infection leading to severe complications, including cirrhosis (liver scarring) and liver cancer in 20–30% of patients.

Hepatitis B virus (HBV) is a deoxyribonucleic acid (DNA) virus belongs to family hepadnaviridae which includes two genera; orthohepadnavirus (infecting mammals) of which hepatitis B virus is the prototype, and avihepadnavirus (infecting birds) of which DHBV is the prototype.

HBV infection affects approximately two billion people worldwide at some point of their lives; among whom 350 million suffer from chronicity of this infection becoming a carrier of this virus.

HBV has been found in virtually all body secretions and excretions. HBV is transmitted primarily through:
• Birth to an infected mother. Between 80–90% of infants infected during the first year of life develop chronic infection.
• Sexual contact with an infected person
• Sharing contaminated needles, syringes, or other injection-drug equipment

• Hepatitis B can also be transmitted through medical and dental procedures, tattooing, piercing, sharing personal hygiene items, razors, and manicure and pedicure material contaminated with infected blood.

HBV is not spread through breastmilk, food or water or by casual contact such as hugging, kissing or sharing food or drinks with an infected person.

Hepatitis B infection acquired in adulthood leads to chronic hepatitis in less than 5% of cases, whereas infection in infancy and early childhood leads to chronic hepatitis in about 95% of cases.
Hepatitis B transmission

Giardiasis: Cycle and mode of transmission

Giardia lamblia, once considered a harmless commensal organism, has become the most common pathogenic intestinal parasite in the United States. Children are at the most risk from the clinical consequences of Giardia infection, particularly those in developing countries and living in disadvantaged community settings.

Outbreaks of giardiasis linked to drinking water and food handlers [2] have been documented. Large, prolonged outbreaks linked to recreational water, particularly chlorinated sources, are less common.

Giardia exists in two forms: the trophozoite is responsible for clinical illness, and the cyst for transmission of infection. Transmission of G. lamblia is by the faecal–oral route, and can be person-to-person, animal-to-person, foodborne or waterborne. The infection is acquired by ingesting cysts, which are excreted in the feces. As few as 10-25 cysts are sufficient to establish an infection in some humans. Some livestock may be infected by as few as 1–10 cysts.

As trophozoites pass through the small intestine they encyst where the trophozoites then multiply. Many of the dividing trophozoites are carried toward the colon, and encyst along the way, in response to bile salts and other stimuli. Cysts can appear in the feces from 3 days to 3 weeks after infection, depending on the host species.

Excretion usually begins around the same time the first symptoms (if any) appear. Cysts voided in the feces are the infective stage and are immediately infective if ingested. The cysts may be transmitted directly from one individual to another under circumstances that are conducive to fecal-oral transfer such as in daycare centers or in environments where hygiene levels are compromised
Giardiasis: Cycle and mode of transmission

Leptospirosis: The Great Mimicker

Leptospirosis is a disease that is caused by spirochete bacteria in the genus Leptospira. There are 10 pathogenic species, and more than 250 pathogenic serovars. Pathogenic leptospires belong to the species Leptospira interrogans, which is subdivided into more than 200 serovars with 25 serogroups.

It is a zoonosis of worldwide distribution, endemic mainly in countries with humid subtropical or tropical climates and has epidemic potential. Leptospirosis is a severe, water-borne disease transmitted from animals to humans, with tens of millions of human cases worldwide each year.

Leptospirosis is also known as “the Great Mimicker” and may be overlooked and underdiagnosed due to its varied clinical presentations. Fatality rates can range as high as 20 to 25 percent in some regions, and it is particularly prevalent in tropical countries where poor people live under highly crowded condition, or in rural areas where people are exposed to water contaminated by the urine of Leptospira.

Feral and domestic animals constitute the reservoir of the agent, transmitted through contact of mucous membranes or (broken) skin with water (swimming or immersion), moist soil or vegetation contaminated with the urine of infected animals; occasional infection occurs through ingestion/inhalation of food/droplet aerosols of fluids contaminated by urine.

Outbreaks of leptospirosis tend to occur after heavy rainfall or flooding in endemic areas, especially areas with poor housing and sanitation conditions.

Symptoms can include fever, headache, myalgia (typically of the calves and lower back), conjunctival suffusion, nausea, vomiting, diarrhea, abdominal pain, cough, and sometimes a skin rash.

Leptospirosis: The Great Mimicker

Yellow fever

Yellow fever is a viral haemorrhagic fever which strikes an estimated 200 000 persons world-wide each year and causes an estimated 30 000 deaths.

The yellow fever (YF) virus is a Flavivirus, which currently contains over 70 viruses, of which most are arthropod-borne, including the dengue viruses. The virus is transmitted by Haemagogus, Sabethes or Aedes aegypti mosquitoes.

Yellow fever outbreaks occur in both rural and urban settings. In urban settings, outbreaks are likely to be larger and are difficult to control.

Yellow fever was an unknown disease until the discovery of the Americas. It probably originated in Africa and was possibly introduced to the American continent by ships carrying slaves and the vector Aedes aegypti. The first epidemic was reported in the American continent, where it is possible to characterize with greater certainty the infection by yellow fever, occurred in the Yucatán peninsula in 1648.

There are three different epidemiological patterns of yellow fever virus transmission: the sylvatic or forest pattern; the Aedes aegypti-borne urban cycle; and an intermediate cycle that bridges these two patterns. The different epidemiological patterns of transmission lead to the same clinical disease.

The incubation period is from three to six days after a bite from an infected mosquito. The classic form of yellow fever is a severe systemic disease with a high case-fatality rate, characterized by fever, prostration, compromised liver, kidney, and cardiac function, hemorrhagic manifestations, and shock. The progression of the disease can include three clinically distinct stages: infection, remission, and intoxication.
Yellow fever

Chikungunya fever: transmission and symptoms

Chikungunya is a mosquito-borne viral disease, caused by the Chikungunya virus (family: Togaviridae, genus: Alphavirus). The disease was documented first time in the form of an outbreak in Tanzania. The name is derived from the ‘makonde’ dialect which means ‘that which bends up’, indicating the physical appearance of a patient with severe clinical features.

In recent decades the Aedes mosquitoes carrying chikungunya have spread to the European Region. In 2007, a chikungunya outbreak was reported for the first time in Italy. In 2013, chikungunya was found for the first time in the Americas and has spread to the Caribbean, South and Central America, and North America.

The virus is transmitted from human to human by the bites of infected female mosquito. Aedes aegypti is the common vector responsible for transmission in urban areas whereas Aedes albopictus has been implicated in rural areas. Recent studies indicate that the virus has mutated enabling it to be transmitted by Aedes albopictus. The Aedes mosquito breeds in domestic settings such as flower vases, water-storage containers, air coolers, etc. and peri-domestic areas such as construction sites, coconut shells, discarded household junk items (tyres, plastic and metal cans, etc.).

Both mosquitoes can be found biting throughout day lighthours, though there may be peaks of activity at dawn and dusk. Both species are found biting outdoors, but Aedes aegypti will also readily feed indoors.

What are the symptoms?
Common symptoms include fever and severe joint pain. Other symptoms may include headache, muscle pain, joint swelling, or rash.ŠSymptoms usually begin 3—7 days after being bitten by an infected mosquito.ŠMost patients will feel better within a week. In some people, the joint pain may persist for months. Death is rare.

Outbreaks are most likely to occur in post-monsoon period when the vector density is very high. Human beings serve as the chikungunya virus reservoir during epidemic periods. During inter-epidemic periods, a number of vertebrates have been implicated as reservoirs. These include monkeys, rodents, birds, and other vertebrates.

Chikungunya fever: transmission and symptoms

Rickettsial infections

Rickettsial infections are caused by bacterial organisms (Rickettsiae), which are found throughout the world. The genus Rickettsia is included in the bacterial tribe Rickettsiae, family Rickettsiaceae, and order Rickettsiales.

Family Rickettsiaceae comprise a group of microorganisms that phylogenetically occupy a position between bacteria and viruses. Rickettsiae are small, non-flagellate, gram negative pleomorphic cocco-bacilli adapted to obligate intracellular parasitism and transmitted by arthropod vectors.

The diseases caused by Rickettsia species are often collectively referred to as rickettsioses. Rickettsiae live in small insects such as ticks, fleas, mites, and lice and can infect mammals (including humans), but cannot survive for any significant period outside their host.

Among returned travelers, rickettsial diseases have been estimated to be the fourth most common cause of fever, with symptoms such as rash, abdominal pain, and a dry, black/dark scab at the site of the infecting bite.

The incubation period ranges from 2-14 days. The disease begins with fever, myalgia and headache. Headache is usually quite severe, young children may not complain of pain at all. Onset of nausea, vomiting, pain abdomen, diarrhea and abdominal tenderness occur in substantial number of patients suggesting gastroenteritis or an acute surgical abdomen.

Tick-borne rickettsioses are often acquired in rural settings in risk areas; however, urban transmission also occurs. Most rickettsial infections are transmitted to humans by the bite or feces of fleas, ticks, mites, or lice. Even the smallest forms of ticks (such as larvae) can transmit the infection to humans, meaning that many infected individuals do not recall a tick bite before symptoms appear.

Rickettsiae microorganisms appear to exert their pathologic effects by adhering to and then invading the endothelial lining of the vasculature within the various organs affected.

Infected ticks and mites transmit rickettsiae primarily through their infected salivary glands directly into the bite. In lice and fleas, rickettsiae do not infect the salivary glands but multiply in the cells of the gut wall and are excreted in the faeces in large amounts, contaminating the skin area around the bite.

The most important pathophysiologic effect is increased vascular permeability with consequent edema, loss of blood volume, hypoalbuminemia, decreased osmotic pressure, and hypotension.
Rickettsial infections

Chickenpox

Chickenpox is the primary infection caused by the varicella-zoster virus. It is an acute, highly infectious disease most commonly seen in children under 10 years old.

Chickenpox is usually a mild, self-limiting illness and most healthy children recover with no complications. Adults tend to suffer more severe disease than children. After recovery from chickenpox the virus stays dormant (inactive) in the nerves near the spine. Years later the virus can become active again and cause herpes zoster, which is also known as shingles.

Chickenpox is highly contagious, infecting up to 90% of non-immune people who are exposed to the disease. The incubation period (the time from becoming infected until symptoms appear) ranges from 10 to 21 days although is usually from 14-16 days. The most common symptoms of chickenpox are an itchy rash with small blisters, fever, tiredness, headache, and loss of appetite. The rash usually develops on the scalp and body, and then spreads to the face, arms, and legs.

Susceptible individuals who have been in contact with a person with chickenpox should be considered potentially infectious from the 10th to the 21st day after exposure.

Transmission occurs from person to person by direct contact with persons with either varicella or herpes zoster (shingles), inhalation of aerosols from vesicular fluid of skin lesions of persons with varicella or zoster, and through infected respiratory secretions that also may be aerosolized.

Recovery from primary varicella infection usually results in lifetime immunity. In otherwise healthy persons, a second occurrence of chickenpox is not common, but it can happen, particularly in immunocompromised persons.
Chickenpox

Viral infection

Viruses are ubiquitous and cause a wide spectrum of disease in humans ranging from asymptomatic infection, severe debilitating illness, and sudden death. Viruses are broadly classified as ribonucleic acid and deoxyribonucleic acid base on the genome.

During infection, a virus must attach itself to a cell that it then commandeers and injects with its nucleic acid. The virus genetic code overrides the host cell’s genetic code, using the host cell to carry out the virus’s activities and to reproduce viral particles that leave the host cell and infection other cells.

Transmission of blood-borne viruses can result from sexual intercourse and maternal-fetal transmission on the community setting, needle stick injury and other exposure-prone procedures in the health-care setting.

Viruses have long been known to cause certain infections diseases, and many of them produce a long-lasting immunity against re-infection by the same virus.

Traditionally, the epidemiological control of most viral infections depends on the isolation of cases, quarantine of contracts, personal protection by infection control measures and mass vaccination, because specific antiviral treatment is generally not available for most viral infections.
Viral infection

Virus mode of transmission

Although human respiratory diseases of viral origin can be virtually indistinguishable clinically, the causative viruses are quite heterogeneous, not only in their virion structure and genome composition but also in the routes by which they transmitted among humans.

Zoonotic viruses replicate in the reservoir animal host and are usually transmitted to human by direct contact or the bite of a hematophagus arthropod.

For example, rabies virus is transmitted by the saliva from a bite of a rabid animal and simian foamy virus can be transmitted by bites from an infected monkey.

Viruses are transmitted either through the mucosal surfaces of the airways, the intestinal or genital tract, or the eye, abrasion of the skin or by directly gaining access to the bloodstream.

Mucosal entry is most common. Viruses, such as influenza viruses, parainfluenza viruses, certain types of adenoviruses or rhinoviruses spread through the airways and are transmitted by droplets at are formed during coughing or sneezing of an infected individual.

Other viruses such a human Papilloma virus (HPV) is spread through sexual contact. HPV may be transmitted through direct contact (oral to genital, oral to oral, skin to skin) although it is typically transmitted through the skin-to-skin route.

Although humans may become ill as a result of the virus, they are generally considered dead-end hosts for many of the viruses because they do not develop sufficient viremia to infect feeding vectors and thus do not contribute to the transmission cycle.
Virus mode of transmission

Anopheles mosquitoes

Malaria is caused by a Protozoan parasites transmitted by female anopheline mosquitoes of the genus Anopheles, as they are the blood-feeders.

There are approximately 422 species of Anopheles mosquitoes throughout the world. Of these, approximately 75 are considered to be important vectors of malaria.

Malaria is primarily transmitted in tropical or subtropical regions by the bite of an infected Anopheles mosquito. As insects are night-active, in general, the bite takes place between sundown and sunrise, specifically inside houses or other kinds of living spaces.

Anopheles can be distinguish from other adult mosquitoes by the way that the female, when taking a blood feed, inclines her whole body at an angle to her victim, whole in the other, culicine mosquitoes, the body is parallel to the skin surface.
Anopheles mosquitoes

Basic information about Zika fever

Zika is spread mostly by the bite of an infected Aedes species mosquito (Aedes aegypti and Aedes albopictus). The Zika virus, first identified in Uganda 1947, is transmitted by the same type of mosquito that carries dengue fever, yellow fever and chikungunya virus.

The viral disease has spread by outbreaks to many different countries, with an ongoing outbreak in Brazil and Puerto Rico; the first diagnosis of Zika virus in the U.S. occurred in Harris County (Houston), Texas, in January 2016.

A mosquito bites an infected person and then passes those virus to other people it bites. These mosquitoes are aggressive daytime biters. They can also bite at night. Zika can be passed from a pregnant woman to her fetus. Infection during pregnancy can cause certain birth defects.

Aedes aegypti

For most people it is a very mild infection and isn't harmful. However, it may be more serious for pregnant women, as there's evidence it causes birth defects – in particular, abnormally small heads (microcephaly). There is no vaccine or medicine for Zika.

Many people infected with Zika virus won’t have symptoms or will only have mild symptoms. The most common symptoms of Zika are: fever, rash, joint pain (with possible swelling, mainly in the smaller joints of the hands and feet), conjunctivitis (red eyes), itching all over the body. Other symptoms include: muscle pain, headache.

 The virus causes born defects in babies born to some infected pregnant women. The CDC has confirmed Zika can spread through sex, usually after a person traveled to an area where Zika has broken out, got the virus, and gave the virus to a sex partner who did not travel. Infected women and men can both pass the virus to sex partners -- even if they haven’t shown symptoms of infection
Basic information about Zika fever

Reference
https://www.cdc.gov/zika/about/index.html 
http://www.webmd.com/a-to-z-guides/zika-virus-symptoms-prevention#1 
http://www.nhs.uk/Conditions/zika-virus/Pages/Introduction.aspx 
http://www.medicinenet.com/zika_virus/article.htm

Plague

Plague, a zoonotic disease is an infectious disease that is caused by the bacterium Yersinia pestis. It is a flea-transmitted disease with hundreds of cases occurring annually over much of the world. The genus Yersinia contain three species that are frequent pathogens of humans Yersinia pseudotuberculosis and Yersinia enterocolitis are enteropathogenic bacteria that cause a variety of self-limiting intestinal infections.

Yersinia pestis is the agent of plague, which is an acute, often fatal disease. Three major types of plague infections, bubonic, septicaemia, and pneumonic, are defined by the nature of the organs colonized by bacteria.

Bubonic plague is an infection of regional lymph nodes, septicemic plague is an infection of the blood stream, and pneumonic plague is an infection of the lungs.

Person to person transmission within ~2 m can take place by respiratory droplets through coughing. It is generally reported that high secondary transmission rates occur women there is poverty and overcrowding.

Plague is treatable disease and responds to antibiotics of diagnosed early. In the initial stages it may present as a non-specific, febrile illness, with symptoms of gastrointestinal or urinary tract infection. It can also present as meningitis.
Plague

How is measles transmitted?

Measles virus causes a potentially serious generalized infection characterized by a maculopapular rash (rubeola). It is one of the most highly contagious infections agents and outbreaks can occur in populations in which less than 10% of persons are susceptible.

Like influenza virus and rhinovirus, measles virus is transmitted by the cough or sneeze of an infected individual.

Chains of transmission commonly occur among household contacts, school children and health care workers. An uninfected person can get measles just by breathing the air in a room that was previously occupied by an infected person. There will be aerosolization of particles from evaporated respiratory secretions called droplet nuclei.

These are small less 5 um particles that may remain suspended in the air for long periods and me be widely disperse by air currents.

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.

Measles virus usually causes no disease symptoms until about ten days after infection. This period of ‘silence’ results because the innate immune system deals so effectively with the initial measles attack that few airway cells are infected and little new virus is produced.
How is measles transmitted? 

Symptoms of dengue fever

Dengue fever is caused by any of four closely related Flaviviruses, DEN-1, DEN-2, DEN-3 and DEN-4.

These viruses are transmitted to humans by the Aedes aegypti mosquito, a domestic, day-biting mosquito that refers to feed on humans.

Dengue fever is known for having a variety of symptoms all of which happen after a sudden high fever.

The fever ranges from 38.8°C to 40.5°C and it may last for two to seven days.

Undifferentiated fever, accompanied by a rash, is an outcome of dengue infection more common among infants and young children.

Older children and adults are more likely to suffer the classical symptoms of dengue fever include:
*severe headache
*backache
*joint pain
*nausea and vomiting
*mild sore throat
*eye pain
*full body rash, including face, hands and feet
*general weakness

Dengue fever may be confused with Colorado tick fever, typhus, yellow fever, or other hemorrhagic fevers. In dengue fever, leukopenia usually present by the second day of fever.

By the fourth day or fifth day, white blood cells have dropped to 2000-4000/FL, with only 2-40% granulocyte.

The bleeding complications that sometimes accompany classical dengue during epidemics are differentiated clinically from those of dengue hemorrhagic fever.
Symptoms of dengue fever

What may cause hepatitis B infection?

Hepatitis B is a serious health problem, and about one third of the world’s population have been exposed to or are currently infected with hepatitis B virus (HBV).

HBV is one of the most common DNA viruses that can cause aggressive hepatitis, cirrhosis and hepatocellular carcinoma. The virus specifically infects liver cells and can cause acute liver damage. 

Approximately 200,000 new HBV infections occur annually in the United States.

Hepatitis B is a blood borne disease. Most people infected with HBV became infected by exposure to infectious blood or bodily fluids. It has been detected in blood, sweat, tears, saliva, semen, vaginal secretions, menstrual blood, and breast milk.

The common ways of getting hepatitis B are by sharing needles and by having unprotected sex. 

Transmission can also occur by contact of mucous membrane with secretions or saliva containing HBV.

The HBV attaches itself it the membrane that surrounds a liver cell and injects its DNA core into the cell. The virus takes over the cell and causes it to reproduce the virus’s DNA instead of the cell’s DNA. When the liver cell is filled with copies of the virus, it bursts.
What may cause hepatitis B infection?

Influenza – Major Occasional Pandemic Outbreaks

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

Dengue Infection

Dengue Infection
Family: Flaviviridae
Genus: Flavivirus

Dengue is a mosquito born infection that has become a global public health concern in recent years.
Major epidemics of dengue have occurred in the Caribbean, South America, the Pacific, Asia, and Africa.

Dengue is a powerful health concern in many countries, especially in areas with urban slums and breeding places for mosquitos. The power of the virus is increased by that fact that at the present time, prospects for control are poor.

Dengue is caused by one of four closely related, but antigenically distinct, virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4). Infection with one of these serotypes does not provide cross-protective immunity, so people living in a dengue-endemic area can have four dengue infections during their lifetimes.

Dengue is transmitted through the Aedes aegyptia, a domestic day biting mosquito common in the tropics. The incubation period is about two to seven days. Infection with dengue viruses produces a spectrum of clinical illness ranging from a nonspecific viral syndrome to severe and fatal hemorrhagic disease. The three clinical profiles include dengue fever, dengue hemorrhagic fever, and dengue shock syndrome.

Dengue fever is a painful but non lethal syndrome characterized by rash, sudden onset of fever, severe headache, and other flu-like symptoms. Dengue hemorrhagic fever results in fluid loss through leaky blood vessels, leading to dyhydration, hypotension, severe jaundice, gastrointestinal hemorrhages and kidney failure.

This can sometimes worsen to dengue shock syndrome which is the most severe form of the disease in which a child can die of shock in hours. Important risk factors include the strain and serotype of the infecting virus, as well as the age, immune status, and genetic predisposition of the patient.

As shown by the doctrine of original antigenic sin, the body has the same immune response as its first infection, even if this is not the appropriate response. This is the problem with dengue infections.

Dengue only causes serious problems such as hemorrhagic fever and shock syndrome during the second infection of a different strain of the dengue virus. Antibody dependent enhancement increases the ability for uptake of the dengue virus via Fc receptors, enhances virion replication, and therefore makes the second infection of a different strain of the dengue virus much more serous then the first strain. ?


Because of the lack of cross protection between the dengue viruses, it is necessary to develop a vaccine protecting against all four dengue serotypes. There is no licensed vaccine for dengue because none of them guard against all for strains of the virus.

The most common method for control is mosquito control, however it is hard to spray using insecticides because the Aedes aegypti live in places hard to reach with pesticides. Other problems with this methods is the appearance of pesticide resistant mosquitos. Control of mosquito breeding is possible by draining stagnant water supplies.
Dengue Infection