Carrie Arnold charts one virus’s journey to American shores.
Even compared to other globetrotting viruses like SARS, chikungunya is a bit of a jet-setter. It first emerged from obscurity about ten years ago, thanks to an outbreak that began in East Africa and has since spread quickly around the world.
Chikungunya, a virus transmitted by the Aedes aegypti mosquito, gets its name from the excruciating joint pain it causes. In the Makonde language of East Africa, chikungunya means “that which bends over”, since many people who are infected are in too much pain to sit up. Although researchers have documented small, localised outbreaks going back several hundred years, chikungunya first emerged as a serious viral threat in the 1950s and 1960s, causing outbreaks in Africa, India and South-east Asia before it disappeared again.
Then, in 2003, chikungunya returned, causing outbreaks in Kenya and other parts of East Africa before travelling eastward across the Indian Ocean. On the island of La Reunion, more than 250,000 people were infected in 2006 – approximately one-third of the population. While it was on La Reunion, the virus picked up a tiny mutation that allowed it to be spread by the Asian tiger mosquito, Aedes albopictus. This was a major concern for public health officials, since the Asian tiger mosquito lives in more temperate climates and opened up large swathes of the globe to potential chikungunya epidemics.
The virus spread to India and then, thanks to a single infected traveller returning home, to the small town of Castiglione di Cervia near Venice, Italy, where 217 people got sick. Continuing its eastward trek, chikungunya then hit Malaysia and Indonesia before reaching the tiny islands that dot the South Pacific. But before the virus could complete its round-the-world tour, it had one major obstacle in its path: the Americas. Although plenty of infected travellers had brought the virus back as a most unwelcome souvenir, the chain of infection stopped there and no other individuals fell ill. Still, epidemiologists feared that it was just a matter of time before chikungunya got a foothold.
Luck ran out in November 2013, when people on the island of Guadeloupe in the Caribbean began complaining of joint pain, rash and fever. Tests quickly confirmed they had chikungunya. From there, the virus spread rapidly through the Caribbean and soon reached mainland South America. In July 2014, the Florida health department announced they had also found localised transmission of chikungunya in several areas in the state.
Although it’s unlikely that chikungunya will cause the large-scale outbreaks seen in the Caribbean and South America – according to Mustapha Debboun, director of mosquito control at the Harris County Health Department – it’s almost certain that there will be smaller, localised outbreaks. Vaccines are in the works, but with nothing currently available, the USA will be facing down yet another tropical disease armed with the ancient but still relatively effective tools of vector control and contact tracing. Everyone hopes that will be enough.