What Is Kyasanur Forest Disease?

Medically Reviewed by Mahammad Juber, MD on October 06, 2022
Written by Parang Mehta
5 min read

Kyasanur forest disease (KFD) is named for the place it was first reported, a forest in Karnataka, India. This disease is caused by a virus that infects rodents, shrews, and monkeys. You can get it while traveling in an endemic area if an infected tick bites you. 

This disease causes fever, headache, and chills. Kyasanur forest disease is a viral hemorrhagic fever, so the disease can cause bleeding and death. No specific treatment is currently available.

Also known as monkey fever, KFD is a viral hemorrhagic fever. The KFD virus is an arbovirus belonging to the Flaviviridae family. Arboviruses are arthropod-borne viruses: i.e., infections transmitted mainly by small animals like arachnids and insects. Most people recover without any complications, but a few people experience complications that affect their nervous system or cause bleeding.

The KFD virus infects rodents, shrews, and monkeys. Ticks spread the infection after biting these animals. You can get infected by the bite of an infected tick and after coming into contact with a sick or recently dead monkey (or another infected animal). 

Human-to-human transmission has not been observed. However, the KFD virus can also infect domesticated animals like cattle, goats, and sheep, which can then spread it to humans via ticks. Otherwise, these animals can't transmit the disease to humans, and drinking milk from these animals also does not transmit the infection.

Most cases occur in the Indian state of Karnataka and its neighboring states. Transmission is highest from January to May.  

The disease begins with abrupt chills and high fever 2 to 7 days after the tick bite. You may have a severe headache and become unable to tolerate bright light (photophobia). The fever lasts for 12 days or more, and you may also experience vomiting, diarrhea, coughing, pain in the back and limbs, fluid-filled blisters, and weakness.

Noticeable bleeding of the gums or nose may start after 3 or 4 days. You may also vomit or cough up blood, and your stools may be black or red because of bleeding in the intestines. Bleeding into the lungs or loss of a large volume of blood in the intestines can cause death. Otherwise, recovery takes 10 to 14 days, during which you may have persistent muscle twitching, severe weakness, and tremors.

KFD is a biphasic illness in about 20% of people. This means that the fever returns after briefly subsiding, and you may notice symptoms affecting your nervous system symptoms are prominent in this phase. You may experience drowsiness, confusion, giddiness, seizures, and unconsciousness. Bleeding may happen in the second phase, too. This phase lasts 12 to 14 days. 

KFD has a 2% to 10% mortality rate.

If you've recently traveled to Karnataka or one of its neighboring states and developed a fever and other symptoms, you should consider the possibility of KFD. This disease can progress rapidly and make you very sick, so consult your doctor early and be sure to share your travel history. The doctor may refer you to an infectious disease specialist for diagnosis and treatment.

The symptoms of many arboviral diseases are similar, so diagnosis may be challenging. If your doctor suspects KFD, though, they can confirm it with laboratory tests focused on:

Haemagglutination inhibition and complement fixation tests are also options, but results take much longer. PCR and ELISA are rapid tests and allow your doctor to diagnose and treat KFD sooner. This is important, as timely hospitalization and treatment can save lives.

There is no specific antiviral medicine available for KFD. The treatment is mainly supportive. Your doctor will prescribe medicines to reduce your fever and pain. They'll also advise you to maintain your hydration levels.

If you have a severe case, the doctors may hospitalize you and treat any dehydration, low blood pressure, seizures, blood loss, unconsciousness, or other complications. They may prescribe intravenous fluids and blood transfusions depending on your clinical condition. 

Since there is no treatment for KFD, prevention is important. Two preventative measures include vaccination and tick avoidance. 

Vaccination. The vaccine against KFD is an inactivated vaccine produced using formalin inactivation of the KFD virus grown in a chick embryo tissue culture. About 70% of people who take this vaccine develop neutralizing antibodies.

Tick bite avoidance. The bites of infected ticks transmit the KFD virus, so avoiding tick bites is an effective way of keeping yourself safe when traveling in areas where this disease is transmitted. Try to:

  • Avoid going into areas where ticks are common. Stay on clear paths and avoid contact with trees, shrubs, and long grass where ticks may be present.
  • Wear clothing that covers you. Expose minimal areas of skin.
  • Tuck your trousers into your socks. This prevents ticks from climbing up your trouser legs.
  • Choose light-colored clothing that lets you see ticks and remove them as soon as possible.
  • Remove any ticks on your skin with tweezers or a similar device. Grasp it near the skin and pull it upwards. Never attempt to squeeze, crush, or burn a tick.
  • Treat your shoes, clothes, and camping equipment with insecticide. 
  • Use insect repellent, such as DEET (diethyltoluamide), on all exposed skin areas.

Your risk of getting KFD depends on your travel location, the season, and your activities. Disease transmission is most common in the Western Ghats areas of Karnataka but has also been reported in the neighboring states of Tamil Nadu, Goa, Kerala, and Maharashtra. Human encroachment into forest areas and climate change have increased the transmission risk. If your travel takes you to forested areas during the high transmission season (January to May), your risk is high. 

Kyasanur forest disease can't easily be eradicated since it is chiefly transmitted between wild animals and ticks. Taking precautions like avoiding tick-infested areas and watching our for ticks, though, can keep you safe from this life-threatening arboviral disease.