The study showed that the rate of brain infection, or encephalitis, from the chikungunya virus is higher than the rate seen in the US due to West Nile virus and similar infections between 1999 and 2007.
Encephalitis was more likely to occur in infants and people over age 65. The incidence rate in infants was 187 per 100,000 people, and 37 per 100,000 people in above-65 population.
Many cases have occurred in the US in people who acquired the virus while travelling, but the first locally transmitted case in the US occurred recently in Florida.
“Since there is no vaccine to prevent chikungunya and no medicine to treat it, people who are travelling to these areas should be aware of this infection and take steps to avoid mosquito bites, such as wearing repellent and long-sleeves and pants if possible,” said study author Patrick Gerardin from the Central University Hospital in Saint Pierre, Reunion Island.
For the study, researchers looked at whether people with neurological symptoms at disease onset were still affected three years later.
The most common symptoms of the infection are fever and joint pain. Most people recover within a week.
For some people, the joint pain can continue for months and even years.
An estimated 30 to 45 percent of the infected persons with encephalitis had persisting disabilities including behavioural changes and problems with thinking and memory skills in infants and post-infectious dementia in previously healthy adults.
The study was published in the online issue of Neurology.