After affecting around 14 lakh people in south India for two years, the chikungunya virus may now spread to Europe and the US, where tropical diseases are almost nil.

A genetic change in the virus has occurred, which will enable Asian tiger mosquitoes (Aedes albopictus) to carry the virus – in addition to the traditional carrier Aedis aegypti.

Researchers discovered how a protein switch allows chikungunya virus to spread to new carriers.

“The virus still causes epidemic in India; hence, chikungunya may spread to regions where Aedes aegypti and Asian tiger mosquitoes live,” Dr Stephen Higgs of the University of Texas, who led the team that discovered the genetic change in chikungunya, told Deccan Herald.

“Due to global warming, these mosquitoes may spread since they love warm climates, and if mosquitoes are present, the pathogens they transmit may soon follow,” he said.

During an epidemic in the Reunion Island in Indian Ocean, it was suspected that something else was carrying the virus because the traditional carrier Aedes aegypti were absent there. It was later found that aegypti’s close relative Asian tiger mosquito was the culprit.

Both mosquito species are present in the US; moreover, the Asian tiger is spreading in Europe, thus making the two continents vulnerable to chikungunya. The mosquitoes will also breed easily in Europe due to favourable conditions created by global warming.

Virus in Italy

A total count of about 292 chikungunya cases were reported from Ravenna and Forli Cesena provinces in north-east Italy.

“An interesting and unusual aspect was the presence of a mutation in the envelope E1 gene, and we concluded that this mutation increases the efficiency of this strain of the virus to infect the Asian tiger,” Dr Higgs said.

Since 2006, chikungunya has infected nine Indian states, including Karnataka and its four neighbours.