New Delhi, Oct. 7: The rapid spread of the chikungunya virus with over 1.2 million people suspected to be infected across India has baffled scientists, but they say it is still unclear whether the virus has killed anyone.
A year after it surfaced in India after a 32-year gap, the chikungunya virus that is transmitted by mosquito bites has spread to 10 states.
The health ministry said today that chikungunya had been confirmed in 1,489 people.
Health officials and a senior virologist investigating the outbreak told The Telegraph today that a small number of deaths among patients who were known to be infected with chikungunya is under investigation. A few apparently healthy patients who had chikungunya suffered from complications such as encephalitis and kidney failure and died, but we cannot yet link these deaths to the virus, he said.
Karnataka has more than 750,000 suspected cases and Maharashtra over 260,000. Several instances of a fever have been reported in a village in North 24-Parganas in Bengal, but it has not been established yet whether the infection is chikungunya. ( )
Andhra Pradesh, Gujarat, Tamil Nadu and Madhya Pradesh are investigating tens of thousands of complaints of fever. Kerala has recorded over 22,000 suspected cases. Seventy deaths have been reported but there is no consensus that chikungunya is the cause.
Virologists said the number of confirmed cases is relatively small 1,489 because samples from only a fraction of patients are analysed. Most patients receive treatment for symptoms high fever and joint pains and get better, never becoming part of an elaborate investigation.
While chikungunya is not known to be fatal, some researchers suspect that a large outbreak of chikungunya on Reunion Island in the Indian Ocean earlier this year may have caused some deaths.
The numbers and rapid geographical expansion of chikungunya is surprising, said a scientist at the National Institute of Virology (NIV).
Studies by NIV suggest that the current epidemic in India is caused by a subtype of the chikungunya virus found in eastern Africa. The subtype may have entered India five years ago.
But the pattern in India mimics the chikungunya outbreak early this year on Reunion Island, which was larger than previous known outbreaks. About 244,000 nearly a third of the islands population was infected.
Scientists from the Pasteur Institute in France have found that the viral strains had distinct molecular features, triggering speculation that mutations may have contributed to its rapid spread in humans.
Until chikungunya surfaced in Karnataka in October 2005, the last recorded cases had occurred in western India in 1973. Researchers say this 32-year gap would leave people susceptible to the virus.
This, NIV scientists say, might explain why the number of cases of dengue is also transmitted by the same Aedes mosquito is much lower than suspected cases of chikungunya.