Kyasanur Forest disease (KFD) is a tick-borne viral hemorrhagic
fever. It’s caused by the Kyasanur Forest disease virus (KFDV), and is native
to the western and central districts of Karnataka State, India. Locally, it’s known
as Monkey Disease or Monkey Fever.
KFD is a member of the virus family Flaviviridae, other members
of this family include Yellow Fever and Hepatitis C.
KFDV was identified in 1957 when it was isolated from a
sick monkey from the Kyasanur Forest in Karnataka (formerly Mysore) State, India.
Since then, between 400-500 humans cases per year have
The vectors of this virus are hard ticks (Hemaphysalis
spinigera). They contract the virus from an infected mammal (e.g. Human,
porcupine, rats) and remain so for life. Rodents, shrews, and monkeys are
common hosts for KFDV after being bitten by an infected tick. KFDV can cause
epizootics with high fatality in primates.
Transmission of the virus
Transmission to humans may occur after a tick bite or
contact with an infected animal, such as a sick or recently deceased monkey. Like
Yellow Fever, no person-to-person transmission has been described to date.
Farm animals (e.g. goats, cows, and sheep) may become
infected with KFD, but play a small role in the transmission of the disease.
These animals provide nourishment (via their blood) for the ticks. It is
possible for a farm animal infected with the virus to infect other ticks;
however, transmission of KFDV to humans from farm animals is extremely rare. Also,
there has yet to be any evidence of disease transmission, to humans, from the
consumption of unpasteurized milk from goats, cows or sheep.
Signs and Symptoms
After an incubation period of three to eight days in the individual,
the symptoms of KFD begin suddenly with chills, fever, and a headache. Severe
muscle pain with vomiting, gastrointestinal symptoms and bleeding problems may
occur three to four days after the initial symptom onset. Patients may
experience abnormally low blood pressure, with low platelet, red blood cell,
and white blood cell counts.
After one to two weeks of symptoms, some patients recover
without complication. However, the illness is biphasic (meaning having
two phases) for a subset of patients (10-20%) who experience a second wave of
symptoms at the beginning of the third week. These symptoms include fever and
signs of neurological manifestations, such as severe headache, mental
disturbances, tremors, and vision deficits.
The estimated case-fatality rate is from 3 to 5% for KFD.
Risk of Exposure
KFD has historically been limited to the western
and central districts of Karnataka State, India. However, in November 2012,
samples from humans and monkeys tested positive for KFDV in the southernmost
district of the State which neighbors Tamil Nadu State and Kerala State,
indicating the possibility of wider distribution of KFDV. Additionally, a virus
very similar to KFD virus (Alkhurma hemorrhagic fever virus) has been described
in Saudi Arabia.
People who live in or visit the rural or outdoor settings
(e.g., hunters, herders, forest workers, farmers) within Karnataka State are
potentially at risk for infection by contact with infected ticks. Seasonality
is another important risk factor as more cases are reported during the dry
season, from November through June.
Diagnosis can be made in the early stage of illness by
molecular detection by PCR or virus isolation from blood. Later, serologic
testing using enzyme-linked immunosorbent serologic assay (ELISA) can be
Currently, the CDC lists no specific treatment for KFD. However,
they do say that early hospitalization and supportive therapy is important.
Supportive therapy includes the maintenance of hydration and the usual
precautions for patients with bleeding disorders.
A vaccine does exist for KFD and is used in endemic areas
of India. Additional preventative measures include insect repellents and wearing
protective clothing in areas where ticks are endemic.
Also, please check yourself for ticks after coming
indoors and be especially thorough if you have body piercings.
I once had a coworker who had a tick just beneath her belly button ring and it
grew to a pretty good size before she noticed it.