Chikungunya: What you need to know

Over the past several months, chikungunya virus infection has become a severe epidemic in the Caribbean and the Americas. The disease has affected thousands of people, and the abundance and wide distribution of its vectors increase the risk for further transmission.

Although only imported cases from travelers have so far been reported in the United States, some experts say clinicians can expect to see autochthonous cases in the country in the near future.

Based on the latest clinical data and breaking news developments, here is what you need to know:

Epidemiology

A relatively new vector-borne disease, chikungunya virus is a member genus Alphavirus, in the family Togaviridae. Its primary vectors are Aedes mosquitoes, which feed during daylight hours and at dusk and dawn.

Chikungunya outbreaks have occurred in countries in Africa, Asia, Europe, and the Indian and Pacific Oceans. Localized outbreaks have also occurred in Italy and France. The disease was absent from the Western Hemisphere until November 2013, when local cases were reported from the the French side of the Caribbean island of St. Martin. Since then, chikungunya has spread swiftly across the Caribbean and the Americas.

There are now more than 130,000 suspected cases of infection, according to the Pan American Health Organization. A total of 4,486 cases have been confirmed, with 14 related deaths. Local transmission has been detected in 17 countries.

Sequencing of the St. Martin virus isolates suggest it is of Asian origin.

Symptoms

Symptoms of chikungunya virus infection include fever, headache, nausea, severe joint and muscle pain, and rash. Although it is rarely fatal, recovery can be protracted, with joint pain lasting for months or even years in rare cases. In most patients, symptoms typically subside within a week.

According to the CDC, symptom onset usually occurs within 3 to 7 days after being bitten by an infected mosquito.

The disease is often confused with dengue.

A threat to the Americas

According to the CDC, the high level of viremia in humans and the wide distribution of A. aegypti and A. albopictus mosquitos — the same vectors that transmit dengue — increase the risk of introducing chikungunya virus into new regions by infected travelers.

In a recent study, researchers assessed the vector competence of 35 of populations of A. aegypti and A. albopictus, collected from 10 countries across the Americas, including the US. The species A. aegypti are common in the Caribbean, Central and South America and in warmer areas of the United States, and A. albopictus mosquitos infest numerous US states. The researchers found that all 35 populations of both mosquito species were susceptible to three chikungunya genotypes belonging to two different lineages (Asian and East-Central-South African), suggesting that even temperate regions are at risk.

In another study, researchers developed a model to predict the likelihood of a chikungunya epidemic in the US at different times throughout the year. According to the model, the chances of an outbreak in New York peaks at 38% if the virus is introduced in August. There is also a significant risk for an outbreak if the virus is introduced after June 15 and through December.

According to Infectious Disease News Editorial Board member Donald Kaye, MD, US clinicians have seen imported cases of chikungunya for years.

Donald Kaye

“For example, as of May 29, the Florida department of health had reported 10 imported chikungunya cases in 2014,” he said. “All individuals had a travel history to a chikungunya-endemic country or area in the Caribbean experiencing an outbreak in the 2 weeks prior to onset (Dominica, Dominican Republic, Haiti and Martinique).

“We can expect autochthonous cases in the US in the future as we have the vector Aedes mosquitos here.”

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Treatment

There is no vaccine to prevent infection with chikungunya. The disease is treated symptomatically.

According to the CDC, chikungunya virus infection should be considered in patients with acute onset fever and polyarthralgia, particularly in travelers returning from endemic regions. Serologic testing can confirm the presence of immunoglobulin M and immunoglobulin G anti-chikungunya antibodies. Cultures may also be used to confirm infection, but with certain precautions, and PCR methods have variable sensitivity, according to WHO.

With no specific treatments available, the focus has been on vector control to stop the spread of disease. Health officials advise the use of insect repellents and permethrin-treated clothing, and to remove any standing water around the house. Long-sleeved shirts and long pants are also recommended.

CDC guidelines for clinicians can be found here.

For more information:

Ruiz-Moreno D. PLoS Negl Trop Dis. 2012;doi:10.1371/journal.pntd.0001918.

Vega-Rúa A. J Virol. 2014;doi:10.1128/JVI.00370-14.