“Globalization, urbanization, and climate change have significantly raised the risk of ‘explosive, unpredictable’ outbreaks of the mosquito-borne disease chikungunya, which disabled millions and likely amassed close to $50 billion in healthcare and disability-related costs in 110 countries from 2011 to 2020."
Mary Van Beusekaum, MS, reporter and editor, CIDRAP News
“To me, there is nothing more soothing than the song of a mosquito that can't get through the mesh to bite you.”
Madison Smartt Bell, American Novelist
Chikungunya is a mosquito-borne viral infection. I didn’t feature chikungunya in my September 18, 2024 Germ Gems post, “Latest Buzz on Mosquito-borne Infections,” but instead focused on West Nile virus (WNV) and Eastern Equine Encephalitis (EEE). At that time, Dr. Anthony Fauci, former director of the National Institutes of Allergy and Infectious Diseases, was recovering from a severe bout of WNV infection, and EEE was spreading in horses and humans in New England. But now, chikungunya is attracting mounting attention following recent analyses indicating that it not only is a very costly emerging infection but that it’s also on the U.S. threshold. Therefore, I felt it time to feature this mosquito-borne viral infection in its own post.
What and where is chikungunya? Chikungunya is a mosquito-borne viral disease that causes fever and severe joint pain. Its name “chikungunya” derives from a word in the Kimakonde language of southern Tanzania, meaning “to become contorted” and describes the stooped appearance of sufferers with joint pain.
Chikungunya is caused by a ribonucleic acid (RNA) virus that belongs to the alphavirus genus of the family Togaviridae. Chikungunya virus (CHIKV) is transmitted to humans by the bites of infected female Aedes aegypti and Aedes albopictus mosquitoes. These mosquito species can also transmit other viruses, most notably dengue virus which chikungunya is often confused with because of the copy-cat symptoms of severe joint and bone pain.
CHIKV was first identified in the United Republic of Tanzania in 1952 and subsequently in other countries in Africa and Asia. Since 2004, outbreaks of CHIKV have become more frequent and widespread. The first local, mosquito-transmitted chikungunya cases in the Americas were reported in late 2013, after which large outbreaks occurred affecting most of the countries in the region. Chikungunya has now been reported in 118 countries in Asia, Africa, Europe, and the Americas.
Before 2006, chikungunya was rarely identified in U.S. travelers. During 2006–2013, an average of 28 people per year in the U.S. tested positive for recent CHIKV infection. All were travelers visiting or returning to the U.S. from affected areas in Asia, Africa, or the Indian Ocean. Beginning in 2014, chikungunya was reported among U.S. travelers returning from affected areas in the Americas, and local transmission was identified in Florida, Texas, Puerto Rico, and the U.S. Virgin Islands.
Symptoms and outcomes. Chikungunya causes fever, severe joint pain (arthralgia), and fatigue. Most cases are self-limited, but the disease can affect the neurological and cardiovascular systems leading to poor outcomes, including death. Worldwide between 2011 and 2020, an estimated 13,000 people died of their CHIKV infections, and the estimated number of disability adjusted life years (DALYs) (i.e. years of life lost due to illness, disability, or death) was 1.95 million.
Economic impact. In a December 2024 report in BMJ Global Health, “The global health and economic burden of chikungunya from 2011 to 2020: a model-driven analysis on the impact of an emerging vector-borne disease,” researchers determined that the total cost of the disease during that period was $49.9 billion, with $25.1 billion spent on chronic disease, reflecting largely the profoundly disabling nature of the severe arthralgias.
The authors of the report suggested, “Insights from this study could inform decision makers on the impact of chikungunya on population health and help them to appropriately allot resources to protect vulnerable populations form this debilitating disease.”
Impact of climate change. The profound influence of global warming on vector-borne infections is a recurring theme in Germ Gems. As I’ve noted before, Aedes mosquitoes have specific climate requirements for survival, and the warming of temperate areas and increased humidity globally have allowed Aedes mosquitoes to transmit chikungunya to new areas. (Aedes mosquitoes can survive during droughts in areas that store water in containers near homes.) Higher temperatures also promote CHIKV replication.
There’s little evidence that efforts to date aimed at curbing global warming are sufficient to control vector-borne diseases (which include malaria and dengue). Therefore, it seems it’s just a matter of time before chikungunya establishes a foothold in the U.S.
There is, however, good news; in 2023, the U.S. Food and Drug Administration approved a chikungunya vaccine. And, at least for now, the Centers for Disease Control and Prevention (CDC) provides up to date information on chikungunya vaccines
Who’s at risk? Who should worry about the global rise in chikungunya? Right now it’s people who live in countries afflicted by the disease (endemic areas) and travelers to these areas. For those living in non-endemic countries like the U.S. right now you need to worry only if you’re planning to travel to an afflicted country. The CDC’s website identifies “Areas at Risk for Chikungunya.”
If you are traveling to such an area, talk to your healthcare provider about the risk and benefits of getting the chikungunya vaccine. This is especially important for persons aged >65 years, particularly for those with underlying medical conditions. At the same time, brush up on the measures recommended to prevent mosquito bites, such as, liberal use of a DEET-containing mosquito spray, and wearing shirts with long arms and pants with long legs. And for the good of public health, remember: Mosquitoes Suck! That is, do everything you can to support efforts to thwart global warming.
Thank you for these important informative newsletters.