Clinicians should be alerted to the possible spread of chikungunya virus in the United States, according to a commentary published online September 23 in the Annals of Internal Medicine.
“Clinicians should advise patients to use antivector measures when traveling to regions with chikungunya transmission,” write Davidson Hamer, MD, professor of global health at the Boston University School of Public Health and School of Medicine in Massachusetts, and Lin Chen, MD, from the Division of Infectious Disease at Mount Auburn Hospital in Cambridge, Massachusetts. “Clinicians should consider chikungunya in the differential diagnosis of febrile travellers with arthralgia and rash after visiting regions with chikungunya transmission, including the Caribbean and Central and South America.”
Chikungunya causes high fevers, rash, and incapacitating joint pains. Most symptoms clear up within 7 to 10 days, although they have persisted for months or years in some people. Severe disease and complications such as meningoencephalitis and death are rare.
Symptoms overlap with dengue virus, and coinfection can occur. Severity and persistence of joint pains help make the differential diagnosis, according to the authors. Clinicians can also use polymerase chain reaction, immunoglobulin M, and immunoglobulin G tests for differentiation..
No licensed treatments or vaccines exist; thus, treatment is supportive using anti-inflammatory agents. In addition, Dr. Hamer and Dr. Chen note that public health efforts should focus on identifying infected travelers and interrupting the transmission cycle, using antivector methods such as insect repellents and drainage of mosquito breeding sites.
Chikungunya means “that which bends up” or “to be contorted” in the Kimakonde language and was first described in the 1950s in Tanzania. It subsequently spread globally, with outbreaks in West Africa, the Indian Ocean, India, and Southeast Asia. Imported cases to France and Italy by travelers from India have also been reported.
In 2013, chikungunya emerged in the Caribbean, where it quickly spread to almost every island, with many cases found in the Dominican Republic and Haiti. In 2014, travelers introduced the virus to Central and South America, where it rapidly became endemic. As of September 5, 2014, the Pan American Health Organization had confirmed 8210 cases and 37 deaths resulting from chikungunya. The continental United States has had 751 reported cases of chikungunya, with local transmission in southern Florida.
Several strains of chikungunya virus exist. The current epidemic is caused by the Asian strain, spread most efficiently by the Aedes aegypti mosquito (which also spreads dengue and yellow fever) and less efficiently by the Aedes albopictus mosquito. Because A albopictus occurs farther north, there is a possibility the virus could spread more widely.
Firm Foothold in the United States Debatable
“I do not think that chikungunya will become established in the northern hemisphere. I think it will closely follow the pattern of dengue virus,” Robert Lanciotti, PhD, chief of the Diagnostic and Reference Laboratory in the Arbovirus Diseases Branch at the Centers for Disease Control and Prevention, Fort Collins, Colorado, commented to Medscape Medical News. “With only a few exceptions in recent history, we have only isolated imported cases [in the United States,] and dengue is not endemic.”
Opinions differ, however. In addition to Florida, the Texas–Mexico border could become a hotbed of chikungunya transmission, Scott Weaver, PhD, director of the Institute for Human Infections and Immunity and scientific director of the Galveston National Laboratory at the University of Texas at Galveston told Medscape Medical News. In that location, dengue has a “pretty regular” transmission pattern that “you might consider that endemic,” he said. And chikungunya could follow a similar pattern.
Americans, who may be most familiar with West Nile, should be aware of Chikungunya’s different transmission pattern, according to Dr. Weaver. A aegypti mosquitoes bite during the day, like to stay inside houses, and have closer associations with humans than West Nile vectors.
“The most important way to protect yourself from chikungunya is to keep mosquitoes out of your house. Here in the US, the main reason we don’t think we’re going to see major outbreaks is because people air condition their houses, or at least have screens that keep mosquitoes out,” Dr. Weaver explained. He added that draining areas of standing water is also important because that is where the mosquito larvae live.
Several chikungunya vaccines are under development. Dr. Weaver’s group is partnered with Takeda Pharma and is working on a live attenuated vaccine that has shown promise in nonhuman primates, he said. Another vaccine recently went into human trials in Europe and uses a measles virus vector. Still another, a non–live replicating vaccine developed by the National Institutes of Health, was “fairly immunogenic” in phase 1 human clinical trials. That vaccine was licensed to Merck but currently has no commercial partner after being dropped by Merck a few months ago, according to Dr. Weaver.
“Scientifically it’s not particularly difficult to develop a chikungunya vaccine, but the financial side of the equation is much harder to work out,” he revealed, “If a vaccine can make it to the market before chikungunya reaches some of the major Latin American cities, it can have a huge public health impact.”
Dr. Hamer reports receiving a grant from the International Society of Travel Medicine. Dr. Chen reports receiving personal fees from Shoreland, Inc; Elsevier Publishing; Springer Publishing; and GlaxoSmithKline. Dr. Weaver reports having a patent for a method of attenuating alpha viruses that could be used in a chikungunya virus vaccine under development. Dr. Lanciotti has disclosed no relevant financial relationships.