The following points will highlight the top eleven viruses associated with Pyrexia. The viruses associated with pyrexia are:- 1. Yellow Fever 2. Dengue 3. Chikungunya 4. O’ Nyong – Nyong 5. West Nile 6. Rift Valley Fever 7. Kyasanur Forest Disease 8. Omsk Haemorrhagic Fever 9. Colorado Tick Fever 10. Sand Fly Fever and 11. Argentinian and Bolivian Haemorrhagic Fever.
Virus # 1. Yellow Fever:
It is primarily a disease of monkeys and forest animals. In nature, the infection is transmitted from monkey to monkey by forest mosquito. Man is only accidentally bitten by an infected mosquito (Aedes aegypti). The human disease may vary from symptomless infection to a severe jaundice with haemorrhage and death.
The disease consists of three periods of infection (viraemia); of remission; of intoxication. The dangerous aspects of the disease are intestinal haemorrhage (black vomit blood altered by the gastric juice), albuminuria, and liver damage etc. The fatality rate is about 5%.
Laboratory diagnosis:
Inoculation of patient’s serum into suckling mice intracellular is a successful method of isolation of yellow fever virus. Yellow fever antibody titre of acute and convalescent sera can be compared.
Prophylaxis:
Under rural condition, it is possible to control mosquito; but it is impracticable in jungle cycle of virus maintenance. Two live attenuated vaccines are available.
Virus # 2. Dengue:
Dengue virus is widely distributed in the tropics and subtropics and transmitted by the genus Aedes. In most cases, the infection is in apparent or clinically mild but it may be a severe diphasic fever; the first stage of fever is characterised by myalgia and arthralgia, photophobia, conjunctivitis; the second stage by rash, sometimes lymphadenopathy. Multiple dengue viruses cause the classical dengue syndrome — haemorrhagic fever.
Virus # 3. Chikungunya:
Chikungunya, the name of the virus, is derived from African word meaning “the thing causing bending up” from the contorted position of patients induced by the joint pain.
Chikungunya virus causes an acute dengue like pyrexia of sudden onset associated with intense joint and muscle pain and a rash.
Virus # 4. O’ Nyong – Nyong:
O’ nyong-nyong:
O’ nyong-nyong virus is related to chickungunya and produces practically identical clinical symptoms except that lymphadenopathy may also occur. The name of the virus has the same meaning as chickungunya. It is prevalent in Uganda.
Virus # 5. West Nile (WN):
West Nile virus occurs in Africa, Egypt, France, Asia, Israel, Mostly children are infected. The infection is clinically mild. Symptoms are fever, sore throat, lymphadenopathy and, sometimes, rash.
Virus # 6. Rift Valley Fever (RVF):
RVF virus is endemic in sheep and cattle in Africa. Man is most commonly infected by handling sick and dead animal but sometimes by mosquito bite.
Virus # 7. Kyasanur Forest Disease (KFD):
KFD virus appeared as a new disease in the Kyasanur forest in Mysore, South India, in 1957.The clinical infection is often mild, characterised mainly by fever, conjunctivitis, vomiting, and diarrhoea. However, severe haemorrhagic cases occur with alimentary tract haemorrhage and epitaxis. Recovery may be slow. The fatality is 10%. The disease is transmitted from dead monkey by a tick (Haemophilus spinigera).
Virus # 8. Omsk Haemorrhagic Fever (OHF):
OHF virus occurs in Russia. Clinically, the disease resembles RFD and is transmitted by rodents (musk M.N.—16 rats) and ticks. Man has been infected by handling the musk rats.
Virus # 9. Colorado Tick Fever:
Colorado tick fever is an in-apparent or mild infection in man, but it may be a severe diphasic fever with haemorrhagic and encephalitis complications in children. It is transmitted from ground squirrels by the wood tick.
Virus # 10. Sand Fly Fever (SF):
SF virus occurs in Russia. The infection in man may be mild or severe fever characterised by myalgia, conjunctivitis. Incubation is 7-10 days. Only man has been shown to be infected. Two serological types of virus are known: Naples and Sicily strains. They are transmitted by sand fly.
Virus # 11. Argentinian and Bolivian Haemorrhagic Fever (Lassa Fever):
The South American haemorrhagic fever is caused by Junin and Machup virus of Tacaribe group. Their main clinical pictures: pyrexia, nasal, intestinal and uterine haemorrhage, petechial and purpura with a fatality rate of 20 percent. It is doubtful if this virus is, in fact, arthropod-borne. Lassa Fever is characterised by severe muscular pain, a haemorrhagic rash and a high case fatality which appeared in 1969 in Americans living at Lassa, Nigeria. Lassa Fever virus also belongs to Tacaribe group.