In the last three months, a relatively rare form of viral fever known as chikungunya has killed at least 300 people across India.

Alappuzha district in central Kerala [Images] has been badly hit by the disease. Nearly 60 people have died in the last three weeks in Alappuzha due to high fever, and the deaths are attributed to chikungunya even as health officials have sent hundreds of blood samples to the National Institute of Communicable Diseases for testing.

Here is a primer on chikungunya and how can it be combated:

What is chikungunya?

Chikungunya is a relatively rare form of viral fever transmitted to humans by infected mosquitoes. Typically the Aedes aegypti mosquito spreads the disease. The World Health Organisation says there are also other competent mosquito vectors that infect the disease that are found in Africa, South-East Asia, southern India and Pakistan. Primarily, it occurs during the rainy season.

Why the name chikungunya?
Chikungunya comes from the Swahili language for stooped walk, reflecting the physique of a person suffering from the disease.

Is the disease fatal?

Generally, health experts say, chikungunya is not fatal. However, in last year, there were 200 deaths due to chikungunya on Reunion Island in southern Africa. In the last three months, there have been some 300 deaths across southern India, in Kerala, Tamil Nadu, Karnataka and Andhra Pradesh. In July, Tamil Nadu had the largest number of cases that were centered around the southern districts of Madurai and Tirunelveli.

What are the symptoms of the disease?

The symptoms of chikungunya appear between four and seven days after the mosquito bite. A high fever and headache occur, with significant pains in the joints (ankles, wrists) that can persist for several weeks. The joints of the extremities in particular become swollen and painful to touch. A rash may sometimes occur. Haemorrhage is rare and all but a few patients recover within three to five days. Some can suffer from joint pain for months. Children may display neurological symptoms. Chikungunya is also known to create complications in young children, pregnant women, the elderly and in persons with underlying diseases.

Does the disease get transmitted between people?
WHO has officially declared that the disease is not transmissible between people.

What is to be done to prevent Chikungunya?

The main preventive measure is to stop the proliferation of mosquitoes by eliminating their breeding ground.

How serious is the situation in Alappuzha in Kerala, where the disease is spreading?

Health officials tackling the disease in Alappuzha said some 60 people have died in the last three weeks and nearly 40,000 people are suffering from acute forms of viral fever. According to K Velayudhan, chief medical officer of Kerala's Alappuzha district, nearly 40,000 people were showing symptoms of the disease. "Blood samples of some of the patients have tested positive for chikungunya," he told rediff.com.

Why is Alappuzha hit by the disease?

Alappuzha has the largest backwater stretch in Kerala. In many places, backwaters are stagnant, creating the breeding ground for mosquitoes.