Kyasanur Forest Disease

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  • Published
    17th Jan, 2019


  • Shivamogga in Karnataka has witnessed number of deaths in the recent past due to the prevalence of Kyasanur Forest Disease (KFD) also known as monkey fever.
  • The prevalence of KFD remains high every year from the month of November to April in the region during which dry spells dominate the region.


What is Kyasanur Forest Disease (KFD)?

  • It is caused by Kyasanur Forest disease virus (KFDV), a member of the virus family Flaviviridae. It was identified in 1957 when it was isolated from a sick monkey from the Kyasanur Forest in Karnataka (formerly Mysore) State, India.
  • Hard ticks (Hemaphysalis spinigera) are the reservoir of KFD virus and once infected, 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.

What are the common modes of transmission?

  • Transmission to humans may occur after a tick bite or contact with an infected animal, most importantly a sick or recently dead monkey. No person-to-person transmission has been described.
  • Large animals such as goats, cows, and sheep may become infected with KFD but play a limited role in the transmission of the disease.
  • These animals provide the blood meals for ticks and it is possible for infected animals with viremia to infect other ticks, but transmission of KFDV to humans from these larger animals is extremely rare.
  • Furthermore, there is no evidence of disease transmission via the unpasteurized milk of any of these animals.

What are the signs and symptoms of the disease?

  • After an incubation period of 3-8 days, the symptoms of KFD begin suddenly with chills, fever, and headache. Severe muscle pain with vomiting, gastrointestinal symptoms and bleeding problems may occur 3-4 days after initial symptom onset.
  • Patients may experience abnormally low blood pressure, and low platelet, red blood cell, and white blood cell counts.
  • After 1-2 weeks of symptoms, some patients recover without complication. However, the illness is biphasic for a subset of patients (10-20%) who experience a second wave of symptoms at the beginning of the third week.
  • The second wave 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%.

Is this disease confined to Karnataka only?

  • No, 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 and Kerala, 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 with recreational or occupational exposure to rural or outdoor settings (e.g., hunters, herders, forest workers, farmers) within Karnataka 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.

Is there any treatment and prevention of this disease?

  • There is no specific treatment for KFD, but early hospitalization and supportive therapy are 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.

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