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It is chikungunya: experts

C. Maya

Among the dead, 80 per cent were aged above 70 years

Thiruvananthapuram: Health Department officials and a central team of experts investigating the viral fever epidemic in Cherthala have dismissed speculation that the disease is not chikungunya.

"There is no doubt that this is an outbreak of chikungunya viral fever because we have already isolated the virus in nine samples here. We cannot predict whether a mutant variant of the virus is responsible for the virulence of the epidemic and the fatalities in this region. It is not likely that some other virus, like the West Nile, could be co-circulating here because it has not been isolated in any of the serum samples," a senior official of the expert team said.

Mutant strain

Scientists at the National Institute of Virology, Pune, in the latest issue of Emerging Infectious Diseases, said the strain circulating in India could be the same mutant strain of chikungunya virus that resulted in the outbreak in Reunion Island early this year.

The mutant strain had African roots, while the previous outbreak reported in India 32 years ago had an Asian lineage, the scientists said.

The European Centre for Disease Prevention and Control, in its report on September 18, said that since the beginning of the outbreak in Reunion Island, 248 deaths had been reported, directly or indirectly related to chikungunya.

It said that 75 per cent of the deaths occurred in persons over 70 years of age, with chronic medical conditions. In infants less than 10 days old, 40 infections were reported.

Chikungunya diagnosis had been confirmed in the mothers of 39 of these infants, indicating viral transmission from the mother to the foetus.

Signs of severity

The signs of severity of the infection included respiratory failure, cardiovascular problems and meningo-encephalitis.

The pattern of clinical manifestations of chikungunya virus and the mortality profile in the ongoing outbreak in Cherthala seem to be similar to those reported in Reunion Island.

In Cherthala also, almost 80 per cent of the deaths attributed to chikungunya have occurred in those in the 70-90 age group, many of whom with underlying medical conditions. A number of neonatal deaths too have been documented.

Scientists of the Pasteur Institute, France, who had done the genome sequencing in six isolates of virus that had caused the Reunion Island epidemic had reported that the mutation undergone by the virus had helped it adapt better to the mosquito.

This explained the manner in which the epidemic had exploded and spread to southeast Asia and India, they said.

No evidence

However, there is no evidence to suggest that the greater neurological virulence of the ongoing chikungunya outbreak in India can be attributed to the mutation.

"We have no evidence for virulence-associated mutations. Our opinion is that most of the deaths reported from Reunion Island occurred in elderly people and others with chronic infections. It would be interesting to know more genetic information about the Indian strains. We have proposed to different Indian institutions and virology labs to exchange genetic information," Isabelle Schuffenecker, scientist at the National Centre for Reference of the Arboviruses, France, said in an in an e-mail to The Hindu .

Though they are probing the deaths attributed to chikungunya, health officials pointed out that the focus now should be on containing the current epidemic through intensive mosquito control measures.

Grim prospect

They said the epidemic could be more severe and uncontrollable if it spread to Ernakulam, the neighbouring district of Alappuzha, which has one of the most urbanised cities in the State.

"Garbage disposal is erratic at Ernakulam. Aedes species of mosquitoes live in your immediate environment, in your flower pots or the water trays of air-conditioners. Chikungunya outbreak in a heavily populated urban area like Ernakulam could turn out to be a nightmare,'' an official said.

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