Chikungunya infections are on the rise among travellers returning to Switzerland, and local cases have been recorded near the Swiss border. Here’s what to know about the mosquito-borne illness and how real the threat is.
Last week WHO spokesperson Diana Rojas Alvarez told the press in Geneva that, as of December 2024, chikungunya had been detected in 119 countries around the world, including Europe, “putting 5.6 billion people at risk”.
It is spreading particularly in Madagascar, Somalia, and Kenya, as well as in South Asia:
Rojas Alvarez added that her organisation was “sounding the alarm early so that countries can prepare in time”.
The chikungunya virus is mainly transmitted by the yellow fever mosquito, Aedes aegypti, but also by the Asian tiger mosquito, Aedes albopictus, the same species that spread the dengue and Zika viruses.
The mosquito becomes a carrier of the virus when it bites a person carrying the pathogen.
According to the Federal Office of Public Health (FOPH), 30 chikungunya infections have already been seen this year among travellers returning to Switzerland – slightly more than double the number in the same period last year.
The Swiss government has been monitoring the mosquito since 2013.
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Risk in Switzerland remains ‘very low’
Since 2007, mosquito-borne transmission of the disease has been reported in mainland Europe on six occasions – all in Italy and France, the WHO said in an epidemiology update.
The largest outbreak was in Italy in 2007 when there were 334 suspected and probable cases.
“Transmission has been driven by Aedes albopictus mosquitoes that are established in the southern and central parts of mainland EU and are expanding in their geographic distribution,” the WHO said.
Although there’s never been a single case of virus transmission in Switzerland, there has been a case not too far from the Swiss border.
Around 100 kilometres from Basel, in Lipsheim near Strasbourg, a person was reported to have contracted the virus from an infected mosquito without having previously travelled abroad.
Authorities are therefore urging people to be more vigilant.
The risk of major outbreaks in Central Europe is not particularly high at present, however.
The pathogen is not yet native to the region and has only been introduced by travellers so far.
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“I consider the risk of major outbreaks in Switzerland to be very low. However, there could be isolated locally transmitted cases, as we are currently observing in France or Italy,” Tobias Suter of the Swiss Tropical and Public Health Institute in Basel told Swiss broadcaster SRF.
The FOPH also considers the risk in Switzerland to be “very low”.
What is chikungunya?
Chikungunya is an infectious disease which is primarily transmitted to humans via the bite of an infected female Aedes mosquito.
It was first identified in Tanzania in 1952 but the disease didn’t circulate widely until the 2000s when there were large outbreaks in Indian Ocean islands and the Caribbean.
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The name itself is a reference to the symptoms. In Makonde, a language spoken by the Bantu people in southeastern Tanzania, chikungungya roughly translates as “that which bends up” or “that which contorts”.
But detecting an infection is very difficult, the Swiss Tropical and Public Health Institute’s Suter told SRF.
“In many cases, an infection causes no or only very mild symptoms,” he said, adding that when symptoms did occur they typically manifested as a sudden rise in high fever, accompanied by severe joint pain and headaches.
Other possible symptoms include muscle pain, joint swelling, and a rash. According to the FOPH, symptoms usually appear seven to nine days (in rare cases three to 12 days) after being bitten by an infected mosquito.
According to the WHO, the joint pain can be very severe and may last for months or even years, although most people recover within a week. It’s generally not fatal but can be life-threatening for the elderly, infants and people with underlying health problems.
There is no person-to-person transmission, but there are reports of the virus being passed on during pregnancy. Otherwise, the virus can only be transmitted by infected mosquito bites.
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How do you protect yourself against it?
According to the WHO, the best protection is to avoid being bitten. Use insect repellents and wear long-sleeved tops and trousers (at day and night).
The tiger mosquito bites repeatedly during the day, the Swiss Mosquito Network said.
However, the most important method to cut viral infections is to reduce tiger mosquito breeding grounds, the WHO said, as tiger mosquitoes lay their eggs in standing water.
Mosquito expert Suter recommends that people who believe they have the virus see a doctor. The virus can be detected with a blood test.
If the disease is confirmed, the WHO recommends rest and plenty of fluids.
There are no specific drugs for chikungunya with treatment directed primarily at relieving symptoms, particularly joint pain.
Currently, there are two vaccines approved in several countries and recommended for at-risk groups.
According to the Federal Office of Public Health, one has been on the European market since June 2024. However, the vaccine has not yet been approved in Switzerland.
How did the virus come to Switzerland?
The WHO’s warning of an epidemic is linked to high levels of global trade and travel, as well as climate change.
More tropical mosquitoes are reaching Europe – and Switzerland – via transport links, and more are able to survive in the country as a result of warmer temperatures.
While the chikungunya virus originally only caused infections in tropical and subtropical regions, there have been around 800 imported chikungunya cases in neighbouring France since May – as well as 12 recorded instances of local transmission.
Mosquito and other pest species that are native to warmer climates are moving further north as weather conditions warm due to climate change, increasing the risk that diseases like chikungunya will become endemic in Central Europe.
Other tropical diseases
The number of dengue fever cases – another tropical disease transmitted by the tiger mosquito – has also increased in Switzerland in recent years. While there were only four cases in 2004, the number rose to 102 in 2012 and 177 in 2013.
In the first half of 2025, 62 cases were reported to the FOPH, which could represent a slight decrease – at the same time last year, the number of cases was 71.
