`Chikungunya can't infect patient twice'

NEW DELHI: Here’s good news for anyone affected by chikungunya this year: the virus is unlikely to infect them ever again. This has been confirmed to TOI by virologists from AIIMS who said that unlike dengue, which can be caused by four serotypes of the virus, the chikungunya virus has only one serotype and hence the risk of repeated infection is minimal.

“Only those suffering co-morbidities such as cancer remain at risk for repeated infection due to their lower immunity,” said Dr Lalit Dar, professor of microbiology, AIIMS, on Friday.

Explaining why chikungunya was so widespread this year after the outbreak a decade ago if the virus was incapable of repeat infection, virologists said there was now a large population that had not been affected in 2006 as well as more patients with compromising medical conditions. Dar pointed out that many people had come to Delhi from other states since 2006. They had not been affected by chikungunya. “A significant number of children born since then are also non-immune to the disease. This explains the higher incidence of chikungunya this year,” said Dar.

According to a study published in ‘Virology Journal’ in 2014 that analysed immunity in the population affected by chikungunya in 1991 in Thailand, infection with one chikungunya strain confers lasting natural immunity, even against other strains.

AIIMS tested 3,500 patients suffering from fever in the last two months. Of them, nearly 2,000 (57%) were confirmed to be suffering from chikungunya. The prevalence of dengue was found to be just 5%. Dr S K Sharma, professor and head of medicine department, said in 10-11 patients they found co-infection of dengue and chikungunya viruses.

AIIMS and the National Centre for Disease Control were tasked with identifying the chikungunya virus in circulation to ascertain whether mutations caused this year’s higher incidence and fatality. But the experts firmly believed that the higher incidence was due to the large pool of non-immune population. “Fatality is rare and seen only in patients with pre-existing illness. You cannot blame chikungunya for the deaths,” averred Dr M C Misra, director, AIIMS.

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A committee set up by Delhi government had also refused to attribute the deaths to chikungunya. The panel reviewed the files of 13 patients who had died after suffering from fever and declared none of them caused by chikungunya. In its report, the committee listed co-morbidities such as sepsis, kidney injury and pneumonia as complications that might have led to the deaths.