By Holly Batterman, MD
Several months ago, doctors from the Global Virus Network questioned whether the United States was ready for the next viral disease threat. Referencing the mosquito-borne virus chikungunya – and noting that it was headed to the United States — the researchers concluded: “This article may have been the first occasion where you’ve seen the word ‘chikungunya.’ But it most assuredly won’t be the last.”[i]
Those words were prophetic. Since that time, the United States has experienced a dramatic uptick in cases of chikungunya infection, according to reports from the Centers for Disease Control and Prevention and Quest Diagnostics.[ii] While the world focuses on the devastating Ebola pandemic in West Africa, the threat of Ebola infection for most individuals in the United States is remote. But other emerging viruses have shown potential to infect large populations across the 50 states — and as a public health threat, chikungunya is near the top of the list.
Chikungunya is an infectious disease that causes fever, rash, and joint pain. Pregnant women who acquire chikungunya infection within one week of delivery can transmit the virus to their baby, which can lead to severe infection, neurological complications, and in some infants, encephalitis. Chronic forms of the disease can be so debilitating that many patients experience health problems for years after the original onset of illness.
Long endemic in parts of Asia and Africa, chikungunya had, until recently, been confirmed in only a few dozen or fewer individuals annually in the United States. Moreover, these patients contracted the virus during travel to Africa or Asia. But that pattern changed several months ago following a chikungunya outbreak in the Caribbean over the winter of 2013-2014. By April 2014, locally acquired cases were identified for the first time in Puerto Rico and the U.S. Virgin Islands. By July, Florida had identified its first locally acquired case. Since then, cases have been found in 47 U.S. states; except for Florida, all cases were related to travel to endemic regions.
My team recently conducted a study on chikungunya which found that more people are being tested – and testing positive — for this virus in the United States than ever. Six hundred and forty two specimens, or about 22% of the total tested we tested for antibodies, were IgG and/or IgM positive, suggesting a diagnosis of chikungunya infection. Besides the CDC and other public health labs, our company is the only entity to provide chikungunya testing services in the U.S., so our study provides a basis for assessing test ordering patterns by physicians for patients.[iii]
Another key finding from our study was that most patients underwent antibody testing well after initial infection, based on antibody patterns in tested specimens. This finding is troubling because early symptoms of chikungunya can mimic other infectious diseases, including dengue fever. While chikungunya is rarely fatal, dengue can be without early detection and prompt medical care.[iv] If the prevalence of chikunguyna and dengue fever grow in the United States, it will be vital that health care providers can make timely and reliable diagnosis of these two infections.
We also found that about one in three patients tested by the molecular technique real-time reverse transcription polymerase chain reaction (RT-PCR) were positive for chikungunya virus. Real-time RT-PCR can detect the virus within the first week of infection, but less reliably afterward, which suggests at least some of these patients were in early stages of illness. This finding is noteworthy because the CDC recommends that infected individuals be protected from additional mosquito exposure during the first week of illness to lessen the risk of further transmission.
Fortunately, people can reduce the possibility of infection with chikunguyna. In areas with virus-carrying species of mosquitos, covering exposed body parts and applying mosquito repellent with active ingredients that include DEET, picaridin, oil of lemon eucalyptus (OLE), PMD or IR3535 is a must.[v] For people traveling to the Caribbean and other tropical vacation hot-spots this winter, these simple preventive measures may help prevent a potentially long and debilitating illness.
Hollis Batterman, M.D., is medical director of Focus Diagnostics, a business of Quest Diagnostics. Focus Diagnostics specializes in emerging infectious disease testing services, including chikungunya and dengue viruses. The company is the first, and continues to be the only, commercial clinical laboratory in the United States to provide antibody and molecular testing services for the chikungunya virus.
[i] Are We Prepared For The Next Viral Disease Threat?, S. Weaver, M. Gallo, S. Hrynkow, The Health Care Blog, April 6, 2014
[ii] Chikungunya virus in the United States, arboNET statistics, Centers for Disease Control and Prevention (CDC) website, December 2, 2014
[iii] Chikungunya Virus Serology Correlation with PCR at a Commercial Laboratory Since Emergence of Chikungunya Virus (CHIKV) in the Americas, M. Batterman, Quest Diagnostics, ICAAC 2014
[iv] World Health Organization, Dengue and Severe Dengue Fact Sheet website, March 2014
[v] CDC, Traveler’s Health, Chikungunya website, October 8, 2014