August 25, 2025
SINGAPORE – The Republic has experienced an uptick in chikungunya infections – caused by a mosquito-borne virus – with reported cases so far in 2025 exceeding the total number seen in 2024.
According to the weekly infectious disease bulletin by the Communicable Diseases Agency (CDA), there have been 21 cases of chikungunya fever in 2025 as at Aug 16, compared with 10 cases reported for the same period in 2024, and 15 cases for the entirety of that year.
Chikungunya infections are also surging worldwide, with the European Centre for Disease Prevention and Control (ECDC) reporting more than 240,000 cases around the globe.
Simply Science examines what is causing the spike in cases and whether Singaporeans should be concerned.
What is chikungunya, and why are infection numbers going up?
Chikungunya is a viral disease, whose symptoms include high fever as well as severe muscle and joint pain.
It is spread by two species of mosquitoes, Aedes albopictus and Aedes aegypti, which are also responsible for spreading other diseases such as dengue and zika.
Like dengue, there is currently no specific treatment for chikungunya.
Chikungunya – which has a mortality rate of fewer than one in 1,000 – is typically less severe than dengue, though its symptoms, such as prolonged joint and muscle pain, can be debilitating for seniors.
CDA cited the presence of the Aedes albopictus and Aedes aegypti mosquito species here and the importation of chikungunya by travellers carrying the virus as risk factors for the spread of the disease.
The agency identified climate change as a factor in chikungunya outbreaks in the Americas, Asia and Europe.
The European Centre for Disease Prevention and Control noted Europe is experiencing longer and more intense transmission seasons for such mosquito-borne diseases as a result of climatic changes, such as rising temperatures and longer summer seasons.
There could also be a virological reason for the spike, said Professor Paul Tambyah, the immediate past president of the International Society for Infectious Diseases.
He pointed to a June article in infectious diseases journal Eurosurveillance, which suggested that the strains responsible for recent chikungunya outbreaks on Reunion island in the Indian Ocean are from the East-Central-South African clade, or subspecies, of the chikungunya virus.
The French territory, which is located about 670km east of Madagascar, reported 47,500 cases as at May.
This means about 5 per cent of the island’s population was infected, resulting in 12 deaths.
The East-Central-South African clade is also responsible for an outbreak in China’s Guangdong province.
In the case of the Reunion outbreak, the strain carries a mutation which makes the virus more easily transmittable by Aedes albopictus mosquitoes, Prof Tambyah noted.
Singapore’s status as a major trade and travel hub means it is inevitably affected by such developments in the region, he said.
Could we see concurrent outbreaks of dengue and chikungunya?
Prof Tambyah stressed that it is important to put matters in perspective, noting that the total number of reported chikungunya cases in Singapore in 2025 to date is fewer than the number of dengue cases per day here in 2024.
There has been a decrease in the number of dengue cases here in 2025, with 2,583 infections reported for the first half of the year, compared with about 10,000 dengue cases over the same period in 2024.
However, he cautioned the country could still see “a lot more” chikungunya cases.
“It is possible that we will see outbreaks of both chikungunya and dengue, but most likely that will happen next year rather than this year, as dengue peaks tend to happen towards the middle of the year,” he said, adding that this would depend on the strains of the viruses which are circulating.
What is Singapore doing to protect people from chikungunya?
CDA advises those living in or travelling to chikungunya-affected areas to take precautions to protect against mosquito bites, such as wearing clothes that cover most of the body, as well as regularly applying effective insect repellent containing chemicals such as Deet or IR3535 as the active ingredient.
The agency said earlier in August that it would review the need for additional public health measures should new information surface suggesting the virus poses an increased risk in Singapore.
In recent years, the Republic has moved to expand Project Wolbachia, an initiative to control the Aedes mosquito population here through the release of lab-grown male mosquitoes infected with the Wolbachia bacteria.
When such mosquitoes mate with females, the eggs produced will not hatch.
“Singapore has one of the world’s best vector control programmes that, together with the programme in Cuba, is routinely cited as a model for the world,” said Prof Tambyah.
Still, it is “very hard to tell” whether the measures taken to deter dengue will work against chikungunya, he said.
The fact that Project Wolbachia specifically targets Aedes aegypti may have, paradoxically, led to relatively more bites from the Aedes albopictus species, he added.
There are currently two chikungunya vaccines available overseas, though neither is available in Singapore, Prof Tambyah said.
One is Ixchiq, a live-attenuated vaccine which uses a weakened form of the virus to prompt an immune response to help prevent disease.
Another, known as Vimkunya, uses a molecule that closely resembles the chikungunya virus to prompt an immune response to help prevent illness.
The authorities here could be waiting for more data amid safety concerns about these vaccines, Prof Tambyah said.
Several countries, including the US and Britain, had temporarily suspended the use of Ixchiq in seniors earlier in 2025 amid reports of serious adverse events, including hospitalisations for cardiac and neurologic issues, and deaths in rare occasions.
“The cornerstone of prevention is still avoiding getting bitten,” said Prof Tambyah.
Simply Science is a series that looks at the science behind everyday questions.