Viral Hemorrhagic Fevers

Hemorrhagic manifestations may occur in a proportion of patients suffering from several viral infections. Examples include; small pox, chicken pox, measles; mosquito borne illnesses like yellow fever, dengue and chikungunya; and the tick borne fevers such as, Kyasanur forest disease, Crimean- Congo hemorrhagic fever, etc.

Some of the significant ones are:

1. South American hemorrhagic fever:

• Two related viruses, Junin and Machupo viruses, cause the Argentinian and Bolivian hemorrhagic fevers respectively.
• Rodents acts as reservoirs and transmission occurs through rodent excreta.

2. Lassa fever:

• One of the most highly publicized hemorrhagic fever.
• Caused by arena virus.
• Natural reservoir is multimammate (connecting link between true mice and rats) rat.
• Rodent excreta act as source of infection.
• The incubation period is 3- 13 days.
• The virus resides in the throat, urine and blood of patients.
• Person to person transmission occurs by droplet infection.
• Commonly seen in Nosocomial infection
• Ribavirin proves to be useful.

3. Marburg and Ebola viruses:

• Marburg disease is a hemorrhagic fever that occurred simultaneously in lab workers in Marburg, Germany.
• The infection started from tissues of African green monkeys who suffered from infection.
• Lab workers exposed to these monkeys acquired the infection.
• Person to person transmission also occurred.
• The virus persists in the body and was isolated after 80 days of the onset of illness.
• Isolation was made from semen and the eye’s anterior chamber.
• Sexual transmission also has been reported.

Ebola virus:

• In 1976, several cases of similar hemorrhagic fever occurred in Sudan and Zaire, with high rates of fatality.
• The causative virus morphologically resembled the Marburg virus, but was different antigenically.
• It has been called as the Ebola virus, after the name of a river, besides which the first case was reported.
• Later in 1979, Ebola re-emerged in Sudan, with serial person to person transmission.
• But the reservoir and the natural history of of the virus was unclear at that time.

Marburg and Ebola viruses are enveloped, single stranded RNA viruses. They have a long tubular or filamentous form. They have been classified as Filoviridae.

4. Hemorrhagic fever with renal syndrome (HFRS):

• This disease, is also known as epidemic hemorrhagic nephrosonephritis and Far Eastern or Korean hemorrhagic fever.
• The virus named, Hantaan virus is the causative agent.
• It is a medium sized, enveloped, acid sensitive, RNA virus .
• The virus belongs to Bunyaviridae family.
• The incubation is about 2 weeks.
• The onset of the disease is with fever and proteinuria (presence of excess protein in urine), followed by hemorrhagic symptoms.
• The virus has been isolated from the blood and urine of infected persons.
• Reservoir host is striped field mice.
• Infection spreads from mice to humans.
• The mode of spread is the rodent excreta.
• Spread among humans is not commonly seen.
• Fever is a mild condition, but it is accompanied by the damage caused to the kidney.
• Infection with Hanataan virus and some antigenically related viruses appear to be common in Asia, Europe and America.

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