Kyasanur forest disease (KFD) is a tick-borne viral haemorrhagic fever endemic to South-western part of India. The disease is caused by a virus belonging to the family Flaviviridae. KFDV is transmitted to humans through the bite of infected hard ticks (Haemaphysalis spinigera) which act as a reservoir of KFDV. Signs and symptoms The symptoms of the disease include a high fever with frontal headaches, chills, severe muscle pain, vomiting, and other gastrointestinal symptoms. 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 count. 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. These symptoms include fever and signs of neurological manifestations, such as severe headache, mental disturbances, tremors, and vision deficits. The convalescent period is typically very long, lasting several months. Muscle aches and weakness also occur during this period, and the patient is unable to engage in physical activities. Cause Virology The KFD virus is a typical flavivirus measuring about 40-60 nm in diameter. The genome of KFDV consists of 10,774 nucleotides of single-stranded, positive-sense RNA encoding a single polyprotein that is cleaved post-translationally into three structural (C, prM/M and E) and seven non-structural (NS1, NS2a, NS2b, NS3, NS4a, NS4b and NS5) proteins. The genome of KFDV is very similar (>92% homologous) to that of Alkhurma Hemorrhagic Fever Virus which is primarily found in Saudi Arabia. These two species both belong to the family Flaviviridae and diverged over 700 years ago and have thus remained geographically separated. Transmission A variety of animals are thought to be reservoir hosts for the disease, including porcupines, rats, squirrels, mice, and shrews. Monkeys are the main amplifying hosts for KFD virus and they are also affected by the virus. The surili Presbytis entellus and the bonnet macaque are very susceptible to the KFD virus. They develop tremendous viremia and infect the ticks. The vector for disease transmission is Haemaphysalis spinigera, a forest tick. Humans contract infection from the bite of nymphs of the tick. Man is a terminal host and there no human-to-human transmission because the human domestic environment does not sustain the ticks. Pathology The pathogenesis of KFDV is not completely understood. Research using mice models found that