Kyasanur Forest Disease (KFD)
is caused by
KFD virus (KFDV)
which is a highly pathogenic member in the family Flaviviridae,
producing a haemorrhagic disease in infected human beings.
In 1957, several dead
monkeys were noticed in the Kyasanur forest in Shimoga district in
Karnataka along with a severe prostrating illness in some of the
villagers in the area. A similar illness has been observed in the
locality a year earlier also. A new arbovirus,
antigenically, related to the
Russian
spring-summer encephalitis complex of viruses
was isolated by investigators from the Virus Research Centre, Poona,
from patients and dead monkeys. It was named the KFD virus after the
name of the place from where the first isolations were made.
KFD has a sudden onset with
fever, headache, conjunctivitis, myalgia and severe prostration. Some
cases develop hemorrhages into the skin, mucosa and viscera. Case
fatality rate is about five per cent.
Outbreaks of the disease
have occurred in the area periodically since it was first identified,
but it has spread only for a few kilometers from the original site in
all these years.
Though human infection is
usually found in certain areas in Karnataka, the virus appears to be
more widespread in distribution as evidenced by KFD antibody in man
and animals in the Kutch and Saurashtra peninsula and sporadically
from other parts of India.
A variant of KFDV,
characterised serologically and genetically as Alkhurma haemorrhagic
fever virus (AHFV), has been recently identified in Saudi Arabia. KFDV
and AHFV share 89% sequence homology, suggesting common ancestral
origin.Alkhumra
virus infection, a new viral hemorrhagic fever in Saudi Arabia.
J Infect. 2005 Aug; 51(2):91-7. Epub 2005 Jan 11
Forest birds and small
mammals are believed to be the reservoir hosts.
Infection is transmitted by
the bite of ticks, the principal vector being Haemaphysalis spinigera.
An infection in monkeys
leads to fatal disease, they are unlikely to be the primary
reservoirs, but only amplifier hosts.
Haemaphysalis ticks may act
as the reservoir to some extent as transovarial transmission of the
virus has been demonstrated in them.
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