SciDev.Net

An outbreak of chikungunya virus in the southern Indian state of Kerala has prompted researchers to develop a new diagnostic test to distinguish chikungunya from dengue viruses.

The kit works as early as the second or third day of symptoms, whereas conventional tests can only detect antibodies a week after infection.

It is important to distinguish between the two diseases as both have initial symptoms of fever and joint pains, and both are spread by Aedes aegypti mosquitoes.

The test uses polymerase chain reaction (PCR) methods that rapidly produce thousands of copies of a gene. It contains two sets of gene probes — one common to all four types of dengue, and another specific to chikungunya.

This is the first test of its kind that can detect dengue and chikungunya viruses at once, say scientists at the Rajiv Gandhi Centre for Biotechnology (RGCB) in Thiruvananthapuram, Kerala.

Preliminary results are encouraging, says Easwaran Sreekumar, a researcher at RGCB's department of molecular microbiology.

The test was developed six months ago as chikungunya cases began to mount in Kerala. The RGCB scientists tested 120 patients' blood samples and accurately picked out four cases of dengue and the remaining chikungunya cases.

The results matched parallel conventional tests for dengue or chikungunya antibodies.

Encouraged by the results, RGCB will now test it in a larger population.

Chikungunya virus reappeared in India in 2006 after a gap of 32 years, with the health ministry reporting 1.3 million cases from 13 states. Officials estimate this year's outbreak in Kerala affected 7,000 people.

The recent chikungunya outbreaks are a different strain from the one reported in the 1970s, the National Institute of Virology's senior deputy director Vidya Arankalle reported at a meeting of the Indian Academy of Sciences in Thiruvananthapuram on Saturday (3 November).