U.S. medical authorities are girding up for the arrival of the nation’s first recorded locally acquired cases of Chikungunya fever. University of Texas Medical Branch at Galveston professor Dr. Scott Weaver believes that the United States will soon record its first locally acquired cases of Chikungunya fever, an emerging tropical disease caused by a virus spread by mosquitoes. Already in the Caribbean, Chikungunya is expected to reach continental North America in the near future, with the the first locally acquired Chikungunya illnesses expected to be seen in the continental U.S in 12 to 24 months, and Texas is high on the list of potential breakout locales.
According to the Centers for Disease Control and Prevention (CDC)/, Chikungunya (Pronunciation: “chik-en-gun-ye”) fever is a viral disease transmitted to humans by the bite of infected mosquitoes — a member of the genus Alphavirus, in the family Togaviridae. There is no specific treatment for Chikungunya fever; and medical care is based on symptomatic treatments, and happily the disease is not usually fatal. The CDC notes that Chikungunya virus was first isolated from the blood of a febrile patient in Tanzania in 1953, and has since been cited as the cause of numerous human epidemics in many areas of Africa and Asia and most recently in limited areas of Europe.
Chikungunya virus is not currently found in the United States, but is known to have arrived the West Indies in Dec. 2013. In February, The Public Health Agency of Canada issued a travel health notice saying cases have been confirmed in the Caribbean islands of Saint Martin, Dominica, Guadaloupe, Martinique, Saint-Barthelemy and the British Virgin Islands — all popular vacation spots for Canadians and Americans. The University of Texas Medical Branch at Galveston has been monitoring the spread of Chikungunya virus for some time, and notes in a release that scientists have long known that the process they call “viral emergence” involves a wide variety of factors. Some are changes in the environment, either generated by natural causes or human activity. Others are internal, arising from accidental changes — mutations — in the virus’s genetic code.
A report by the Examiner’s Charles Simmons cites Dr. Kristy Murray, — an associate professor and associate vice chair of research in the department of pediatrics at BCM and director of the Laboratory of Viral and Zoonotic Diseases at Texas Childrens Hospital in Houston and a member of the National School of Tropical Medicine — commenting on a Chikungunya surveillance study to be conducted by the Texas Children’s Hospital and Baylor College of Medicine from April 1 to Oct. 31. Dr. Murray told Simmons that for the next seven months, all children presenting at the Texas Children’s Hospital emergency department with a fever and has blood drawn will have additional testing performed on their specimen to detect the presence, if any, of antibodies to the West Nile virus, all four of the Dengue viruses and all the serotypes of the Chikungunya virus, and that she strongly believes physicians, in and out of the Houston area, need education about both dengue and Chikungunya infections.
Dr. Kristy Murray is an associate professor of Pediatrics in the section of Pediatric Tropical Medicine at Baylor College of Medicine. She is also a member of the National School of Tropical Medicine. Prior to joining the faculty at Baylor, Dr. Murray was an Associate Professor of Epidemiology for the Center for Infectious Diseases at the University of Texas Health Science Center at Houston, School of Public Health (2002-2012). She spent the first five years of her career at the Centers for Disease Control and Prevention where she served two years as an Epidemic Intelligence Service Officer conducting outbreak investigations. In 2002, Dr. Murray returned to Texas and joined the faculty at the University of Texas Health Science Center at Houston. Her research over the past 10 years has been focused on vector-borne and zoonotic diseases, including West Nile virus, dengue, St. Louis encephalitis, eastern equine encephalitis virus, Rocky Mountain Spotted Fever, Chagas, and rabies. She has made numerous discoveries regarding health outcomes related to West Nile virus infection, including identifying persistent infection of the kidneys in patients years past their initial infection, which has never before been reported. She teaches graduate-level courses on epidemiology and infectious diseases, and advises master’s and PhD-level students, serves on the editorial board of the journal Epidemiology and Infection and has authored more than 40 scientific and technical papers.
Chikungunya virus is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on a person infected with Chikungunya virus. Infected mosquitoes can then spread the virus to other humans when they bite. Monkeys, and possibly other wild animals, may also serve as reservoirs of the virus.
The Aedes aegypti (the yellow fever mosquito), a species that breeds in household containers, is an aggressive biter during the day, and is attracted to humans for bloodmeals, is the principle vector responsible for transmitting the Chikungunya virus to humans. Aedes albopictus (the Asian tiger mosquito) an invasive species that was first discovered in the continental U.S. in the mid 1980s, has also played a role in human transmission in Asia, Africa, and Europe. Various forest-dwelling mosquito species in Africa have been found to be infected with the virus.
A UTMB research article published in August, 2011 in the journal PLOS Pathogens titled “Novel Chikungunya Vaccine Candidate with an IRES-Based Attenuation and Host Range Alteration Mechanism” (PLoS Pathog. 2011 Jul;7(7):e1002142. doi: 10.1371/journal.ppat.1002142. Epub 2011 Jul 28.) coauthored by Kenneth Plante, Eryu Wang, Charalambos D. Partidos, James Weger, Rodion Gorchakov, Konstantin Tsetsarkin, Erin M. Borland, Ann M. Powers, Robert Seymour, Dan T. Stinchcomb, Jorge E. Osorio, Ilya Frolov, and Scott C. Weaver, contains a great deal of background on the Chikungunya virus, describes on thoroughgoing detail the process of developing a CHIK vaccine, and concludes that a novel CHIK vaccine candidate, CHIKV/IRES, was generated by manipulation of the structural protein expression of a wt-CHIKV strain via the EMCV IRES. This vaccine candidate exhibits a high degree of murine attenuation that is not dependent on an intact interferon type I response, yet is highly immunogenic and protects against CHIKV challenge. They noted that this promising vaccine candidate is being tested in nonhuman primates to determine if it is suitable for evaluation in humans.
The CDC says Chikungunya fever can cause debilitating illness, most often characterized by fever, headache, fatigue, nausea, vomiting, muscle pain, rash, and joint pain. The term ‘Chikungunya’ means ‘that which bends up’ in the Kimakonde language of Mozambique. Acute Chikungunya fever typically lasts a few days to a few weeks, but as with West Nile fever, which is well-established in North America, and dengue fever — another tropical disease expected to become problematical here soon, as well as other arboviral fevers, some patients have prolonged fatigue lasting several weeks. Additionally, some Chikungunya patients have reported incapacitating joint pain, or arthritis which may last for weeks or months. The prolonged joint pain associated with Chikungunya virus is not typical of dengue. No hemorrhagic cases related to Chikungunya virus infection have been conclusively documented in the scientific literature. Co-circulation of dengue fever in many areas may mean that Chikungunya fever cases are sometimes clinically misdiagnosed as dengue infections, therefore the incidence of Chikungunya fever could be much higher than what has been previously reported.
Chikungunya’s incubation period can be 2-12 days, but is usually 3-7 days. “Silent” Chikungunya virus infections (infections without illness) do occur, but how commonly this happens is not yet known. Chikungunya virus infection (whether clinically apparent or silent) is thought to confer life-long immunity.
Pregnant women can become infected with Chikungunya virus during all stages of pregnancy and have symptoms similar to other individuals. Most infections occurring during pregnancy will not result in the virus being transmitted to the fetus. The highest risk for infection of the fetus/child occurs when a woman has virus in her blood (viremic) at the time of delivery. There are also rare reports of first trimester abortions occurring after Chikungunya infection. Pregnant women should take precautions to avoid mosquito bites. Currently, there is no evidence that the virus is transmitted through breast milk.
There is no vaccine or specific antiviral treatment currently available for Chikungunya fever. Treatment is symptomatic and can include rest, fluids, and medicines to relieve symptoms of fever and aching such as ibuprofen, naproxen, acetaminophen, or paracetamol. The CDC says aspirin should be avoided. Infected persons should be protected from further mosquito exposure (staying indoors in areas with screens and/or under a mosquito net) during the first few days of the illness so they can not contribute to the transmission cycle.
The CDC advises that the best way to prevent Chikungunya virus infection is to avoid mosquito bites, since there is no vaccine or preventive drug currently available. Chikungunya prevention methods are similar to those for other viral diseases transmitted by mosquitoes, such as dengue or West Nile, and include use of insect repellent containing DEET, Picaridin, oil of lemon eucalyptus, or IR3535 on exposed skin; wearing long sleeves and pants (ideally treating clothes with permethrin or another repellent).
Have secure screens on windows and doors to keep mosquitoes out. Additionally, a person with Chikungunya fever should limit their exposure to mosquito bites to avoid further spreading the infection. The person should use repellents when outdoors exposed to mosquito bites or stay indoors in areas with screens or under a mosquito net.
Read the Traveler’s Health Yellow Book for more information on Protection against Mosquitoes, Ticks, Fleas & Other Insects and Arthropods.
Besides taking precautions against mosquito bites. The Public Health Agency of Canada website has advice and up-to-date alerts on viral, parasitic and bacterial disease outbreaks in various countries.
University of Texas Medical Branch at Galveston
Baylor College of Medicine
Texas Childrens Hospital
Centers for Disease Control and Prevention
Proceedings of the National Academy of Sciences
Western Regional Center of Excellence for Biodefense and Emerging Infectious Diseases Research
The Public Health Agency of Canada
Centers for Disease Control and Prevention