Flaviviridae

Flaviviridae

Flaviviruses virions are spherical, enveloped, and 40-50 nm in diameter. Flavi contains a linear, plus sense, single-stranded RNA genome. There are about 70 recognized diseases in the Flavi family. 13 cause disease in humans, such as Yellow Fever, Dengue, and West Nile.

http://education.expasy.org/images/Flaviviridae_virion.jpg

Dengue

DENGUE

There would be three types of virus related to Flavivirus I am going to talk about in the website. But In this post I would be talking about one particular disease that is cause by the Flavi family that greatly affects the lives of humans.

The Dengue virus is a member of the virus family Flaviviridae and is transmitted to people through the bite of the mosquitos Aedes aegypti and Aedes albopictus. Dengue is mainly found in the tropics because the mosquitoes require a warm climate. A major fear of epidemiologists is that the mosquitoes will develop resistance to cooler climates and then be able to infect people in the United States and other temperate climates. The virus is transmitted when a mosquito of the Aedes genus bites an individual infected with dengue virus.

http://www.nd.edu/~lumen/2007_06/images/aedes_aegypti_lumen.jpg

The Dengue virus has been shown to have 4 subtypes. These 4 subtypes are different strains of dengue virus which are DEN-1, DEN-2, DEN-3 and DEN-4.

Symptoms and outcome:

After a person is infected with dengue, they develop an immune response to that dengue subtype. However, if another subtype of dengue virus infects the individual, the virus will activate the immune system to attack it as if it was the first subtype as it have very similar surface antigen.

Dengue fever:

• Many infections asymptomatic
• Acute infection resulting in fever, severe headache, retro-orbital pain, nausea and vomiting.
• Severe muscle and bone pain
• Severe arthralgia
• Maculopapular rash

Dengue haemorrhagic Fever:

• Severe prostration, hypotension, circulatory collapse, bleeding and shock
• Bleeding-petechiae in skin, mucous membrances, injection and punction sites, Gastrointestinal bleeding and haemorrhagic pneumonia.

Prevention and management

Primary prevention of dengue mainly resides in mosquito control. There are two primary methods: larval control and adult mosquito control. In urban areas, Aedes mosquitos breed on water collections in artificial containers such as plastic cups, used tires, broken bottles, flower pots, etc. Periodic draining or removal of artificial containers is the most effective way of reducing the breeding grounds for mosquitos. Larvicide treatment is another effective way to control the vector larvae. Prevention of mosquito bites is another way of preventing disease. This can be achieved by using insect repellent, mosquito traps or mosquito nets.





This graph shows the number of cases in people in Singapore that had been infected with dengue from 2007 to the beginning of 2009.


http://www.dengue.gov.sg/

This video would explain on how the mosquito breed and infect host to spread the virus.

Yellow Fever

Yellow Fever

This post is the continuation for the flavivirus which I am going to talk about another disease cause by the Flavi family that greatly affects the lives of humans.

Yellow fever is an acute viral disease. It is an important cause of hemorrhagic illness in many African and South American countries despite existence of an effective vaccine. Yellow fever virus is transmitted by mosquitoes to human beings. The virus is also preserved in mosquito eggs through their incubation period, thus ensuring existence of the virus each year. Yellow fever is located only in Africa and South America.

Symptoms and outcome: http://www.safely.travel/wiki/images/2/2e/Global_distribution_of_Yellow_Fever.gif

Although some people experience no symptoms, others enter an acute phase, characterized by fever, muscle pain (especially backache), shivers, loss of appetite, nausea and/or vomiting. An indication of yellow fever infection is that the high fever is associated with a relatively slow pulse. After 3 or 4 days, most patients improve, but an estimated 15% enter a toxic phase, marked by a reappearance of fever, jaundice, abdominal pain, vomiting, and bleeding from the eyes, nose, mouth, vomit, and feces. Half of these patients in the toxic phase die within 10-14 days.

Prevention and management

A yellow fever vaccine is available and should be taken by travelers to endemic areas. It is a safe, effective live virus vaccine that has been used for several decades and confers immunity for 10 years or more. Side effects occur in very few vaccines. Four groups of people should not receive the vaccine: infants under 6 months, pregnant women, persons hypersensitive to eggs (the vaccine is developed in embryonic eggs), and immunosuppressed persons.

http://www.cambridgenetwork.co.uk/object/news/43564/img/mosquito_color_index.jpg

Because the virus is transmitted by mosquito, effective protection against mosquitos results in effective protection against yellow fever. This includes the use of insect repellant, protective clothing, and mosquito netting.




This picture states the number of people infected with yellow fever from 1980 to 2007.

http://www.who.int/immunization_monitoring/diseases/YF_coverage.jpg

This video below tell us that yellow fever is no laughing matter hence when there was a outbreak of yellow fever in brazil in 13 January 2008, many people were not immune to this virus hence there was a long to queue of people who needed vaccination of the virus.

West Nile Virus

WEST NILE VIRUS

This is the last post relating to flavivirus which I am going to talk about a disease cause by the Flavi family that greatly affects the lives of humans.

West Nile virus is a virus of the family Flaviviridae. Part of the Japanese encephalitis antigenic complex of viruses, it is found in tropical and temperate regions. It mainly infects birds, but is known to infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels and domestic rabbits. The main route of human is through the bite of an infected mosquito.

Symptoms and outcome:
Less severe symptoms
· -Mainly mild to no symptoms
· -Fever http://sitemaker.umich.edu/section9group5/files/trans.gif
· -Headache, body aches
· -skin rash
· -swollen lymph glands

More severe symptoms
· Crossing blood-brain barrier
· Encephalitis
· Meningitis

Prevention and management
West Nile control is achieved through mosquito controls, by elimination of mosquito breeding sites, larviciding active breeding areas and encouraging personal use of Mosquito repellent. The public is also encouraged to spend less time outdoors, wear long covering clothing, apply bug repellent.

This graph shows the number of people infected with the west nile virus in the US.









http://health.state.tn.us/ceds/wnv/graph.jpg

This video tells us the status of West Nile virus in the US.