Chikungunya Heads To The U.S
If a person returns from traveling [carrying] the virus, a mosquito may bite that person, become infected, and bite another person.
The Chikungunya virus (CHIKV) was first isolated from a patient in Africa in the early 1950s.
Chikungunya means “bent up” in the Bantu language, referring to the posture CHIKV causes from a severe viral arthritis. In its chronic stage, the virus can mimic rheumatoid arthritis (RA). 1
CHIKV is known to cause large outbreaks with high attack rates. The virus received global attention in 2005 when outbreaks in the Indian Ocean islands affected more than 250,000 people. On some islands, infection rates ranged from 34 to 75%.1 In 2013, the disease spread out of the Eastern Hemisphere into the Caribbean. 2
“Chikungunya is now spreading through the Caribbean and Central America like a wildfire,” said Davidson Hamer, MD, professor of global health and medicine at the Boston University School of Public Health and School of Medicine. “With the number of Americans who vacation in the Caribbean, it was only a matter of time before cases showed up in the United States.”
Incidence and Etiology
Since CHIKV became a notifiable condition in 2015, the Centers for Disease Control and Prevention (CDC) has reported 78 locally transmitted cases in Puerto Rico and the Virgin Islands. As of the end of May, a total of 146 cases have been reported in the United States, but all were in travelers returning from affected areas. 3
“Chikungunya is still exceedingly rare in the United States, but it is not hard to imagine that there are or will be some locally transmitted cases. If a person returns from traveling [carrying] the virus, a mosquito may bite that person, become infected, and bite another person,” said Jennifer Layden, MD, PhD, assistant professor in public health and infectious disease at Loyola University Medical System in Maywood, Illinois.
CHIKV is spread by the Aedes aegypti and Aedes albopictus mosquitoes, which are common in areas of the tropics and subtropics. Both types aggressively bite in the daytime instead of being active mostly at dawn and dusk like typical mosquitoes[JR1] . 1,2 “These are the same mosquitoes that transmit dengue fever. It is possible that chikungunya has been around a lot longer than we think but was diagnosed as dengue,” said. Hamer.
Signs and Symptoms
“The incubation period may be about five to seven days. Fever and joint pain are the most common symptoms. There may also be headache, rash, and muscle aches,” said Layden. Symptoms start abruptly, and the fever may be quite high. A maculopapular rash occurs in about 50% of cases. Some people may have lymphadenopathy, nausea, vomiting, and conjunctivitis.1,2
In most cases, symptoms will clear spontaneously in seven to 10 days.2
“In about 5 to 10% of cases, joint pain and swelling may last for months or years. In these patients, the infection mimics rheumatoid arthritis, although there is no evidence that the infection triggers or becomes rheumatoid arthritis,” said Hamer.
Diagnosis and Treatment
Health care providers can diagnose CHIKV with direct detection of the virus using polymerase chain reaction (PCR) or serology detection of CHIKV IgM and IgG antibodies, but the tests may need to be sent to the CDC or to a state health department laboratory. [1,2] “PCR can detect the virus in the first few days. IgM and IgG can be detected after four to five days,” said Hamer.
“Treatment is supportive. With rest, fluids, and NSAIDs, most people will be better in seven to 10 days,” says Layden. CHIKV does not respond to any antiviral therapy. Although researchers have started to develop a vaccine, there is not one available at this time.1,2 “In areas where the infection has been common, doctors have used disease-modifying antirheumatic drugs for long-lasting joint symptoms,” added Hamer.
CHIKV and RA
“Chikungunya infection is not likely to be confused with rheumatoid arthritis for the majority of cases that are self-limited. In these cases, symptoms come on suddenly and are gone quickly,” said Layden.
In cases where joint symptoms last long after the acute phase of the infection, CHIKV can be a good mimic of RA. CHIKV causes pain and swelling in distal joints of the hands, wrists, feet, and ankles. As with RA, there may be morning stiffness, and the distribution is symmetrical. These symptoms may meet the American College of Rheumatology (ACR) criteria for seronegative RA.1,4
CHIKV may also have some overlapping immunologic features. A 2015 study, published in Arthritis & Rheumatology, found that eight of 10 confirmed CHIKV patients met ACR criteria for seronegative RA and developed very similar peripheral T cell phenotypes. The study concluded that rheumatologists need to be aware of these similarities and consider CHIKV when evaluating patients referred for RA.4
“The most important thing for primary care providers is to be aware of this emerging viral infection. To diagnose chikungunya, you need a high index of suspicion. Care givers should consider testing for anyone with sudden onset of the symptoms who has traveled in an area where the infection is common,” said Layden.
“Primary caregivers should also warn patients who may be traveling to the Caribbean or to Central or South America on vacation. These mosquitoes are daytime biters. Use DEET or a picaridin-containing mosquito repellent during the day in these areas. Patients who come down with the infection should be warned that the arthritis symptoms could be severe and long lasting,” said Hayden.
Medically reviewed by: Pat F. Bass III, MD, MS, MPH