The mosquito-borne chikungunya virus has been the subject of increasing attention as it spreads throughout South America, Central America, the Caribbean and Mexico. This painful and potentially debilitating disease is predicted to soon spread to the U.S.
The University of Texas Medical Branch at Galveston’s Scott Weaver, globally recognized for his expertise in mosquito-borne diseases, has been studying chikungunya for more than 15 years. Weaver and fellow infectious disease expert Marc Lecuit of the Institut Pasteur have summarized currently available information on this disease in the March 26 edition of the New England Journal of Medicine.
Since chikungunya was first identified in1952 in present-day Tanzania, the virus has been confirmed in other African countries, Asia, The South Pacific and Europe. In Dec. 2013, the first locally acquired case of chikungunya in the Americas was reported in the Caribbean.
Since then, chikungunya has been identified in 44 countries or territories throughout the Americas with more than 1.3 million suspected cases reported to the Pan American Health Organization from affected areas.
Symptoms appear about three days after being bitten by an infected mosquito. The most common symptoms and signs are fever and severe joint pain and may include headache, arthritis, muscle pain, weakness and rash. Some patients will feel better within a week but others develop longer-term joint pain that can last weeks to years. Death is rare but can occur. People at increased risk for severe disease include young children, older adults and people with medical conditions such as diabetes or heart disease.
Other than anti-inflammatory drugs to control symptoms and joint swelling, there are no specific therapies to treat infected persons and no licensed vaccines to prevent chikungunya fever.
What is chikungunya virus?
The virus is mainly “spread from person to person through mosquitoes,” says Kristy Murray, DVM, PhD, an infectious disease specialist in Houston.
It’s pronounced “chik-en-gun-ye.”
‘‘It’s an African word, and it translates to ‘that which bends up,’” Murray says, because people bend up with joint pain, one of the most common symptoms.
Where did it come from, and how does it spread?
Scientists believe the virus originated in 1952 in southern Tanzania. Chimpanzees or other animals were probably first infected, says Amesh Adalja, MD, an infectious disease specialist in Pittsburgh.
Mosquitoes that bit these animals became infected, then bit and infected people.
The virus can stay in a person’s system for about a week, according to the World Health Organization.
When a mosquito feeds on an infected person, the mosquito can become infected and can bite and infect others.
The Aedes aegypti and Aedes albopictus mosquitoes transmit chikungunya. They also transmit dengue fever, another disease caused by a virus.
“Chikungunya continues to be a major threat to public health around the world,” said Weaver. “Until there is a treatment or vaccine, the control of chikungunya fever will rely on mosquito reduction and limiting the contact between humans and the two virus-carrying mosquitoes, Aedes aegypti and Aedes albopictus.”
These efforts generally focus on reducing or treating standing water and water storage containers where eggs are laid and larvae develop as well as wearing protective clothing and/or insect repellent.
Current research is focused on better understanding how exactly the virus enters and multiplies within the human and mosquito body. Researchers are also learning more about why some people develop long-term chronic joint pain after the initial chikungunya fever while others do not.
Where has chikungunya been found?
In the past decades, outbreaks have occurred in Africa, Asia, Europe, and the Indian and Pacific Oceans.
The virus was found for the first time in the Americas on Caribbean islands in late 2013. More than 20 Caribbean and South American countries and territories have reported outbreaks, according to the CDC.
As of July 17, 243 travel-associated cases, in people returning from the Caribbean or Asia, have been reported in 31 states and the U.S. Virgin Islands, according to the CDC.
On July 17, the CDC reported the first locally transmitted case of chikungunya in Florida, in a male who hadn’t traveled outside the U.S.
“CDC officials believe chikungunya will behave like dengue virus in the United States, where imported cases have resulted in sporadic local transmission but have not caused widespread outbreaks,” the agency said in a statement.
Puerto Rico has 121 locally transmitted cases, and the U.S. Virgin Islands have two.
What are the symptoms?
“Usually fever, rash, muscle aches, and joint pain,” Adalja says.
Headache and joint swelling can also happen.
“When a person first becomes sick, they will think they have a flu-like illness,” Murray says.
Symptoms first appear about 4 to 7 days after the bite, according to the World Health Organization.
A high percentage of those infected become sick, Murray says. She estimates that 90% of those bitten will develop symptoms.
Several promising chikungunya vaccine candidates have reached late preclinical or phase one clinical testing, but final development will require major commercial investments. Another challenge to vaccine development lies in targeting locations where there will be many cases of chikungunya fever to set up and conduct clinical trials.
Weaver is the director of the UTMB Institute for Human Infections and Immunity, scientific director of the Galveston National Laboratory and leads the Global Virus Network’s Chikungunya Task Force.
University of Texas Medical Branch at Galveston
New England Journal of Medicine