EXPLAINER: What you need to know on the return of Chikungunya

On June 4, 2025, Mombasa County announced that it was grappling with a chikungunya outbreak.

Health officials confirmed that 25 positive cases out of 45 samples analysed by the Kenya Medical Research Institute (KEMRI). 

The most affected sub-counties are Mvita, Nyali, Likoni and Kisauni. 

What is Chikungunya?

Chikungunya is a mosquito-borne viral disease transmitted by infected female Aedes aegypti and Aedes albopictus mosquitoes. 

Unlike other mosquitoes that bite at night, the Aedes mosquitoes prefer to bite during the day.

The disease is caused by the chikungunya virus (CHIKV), an RNA virus in the alphavirus genus of the family Togaviridae.

The name chikungunya derives from a word in the Kimakonde language of southern Tanzania, meaning “that which bends up” and describes the contorted posture of infected people with severe joint pain.

According to the World Health Organisation (WHO), chikungunya was first identified in Tanzania in 1952 and subsequently in other countries in Africa and Asia.

The health organisation says urban outbreaks were first recorded in Thailand in 1967 and India in the 1970s.

Since 2004, outbreaks of CHIKV have become more frequent and widespread.

WHO said large outbreaks and sporadic cases are reported mostly in the Americas, Asia and Africa, and occasional smaller outbreaks in Europe.

The symptoms of chikungunya are similar to those of dengue and Zika, making it easy to misdiagnose and making it more difficult for countries to accurately determine the number of people infected.

Symptoms typically appear between four to eight days after a bite and include high fever, severe joint pain, headache, muscle pain, skin rashes, nausea and extreme fatigue. 

While the disease is self-limiting and often resolves on its own, young children, the elderly, and individuals with underlying health conditions are at higher risk of complications. 

According to WHO, most patients recover fully from the infection; however, occasional cases of eye, heart and neurological complications have been reported with chikungunya infections. 

Patients with severe disease require hospitalisation because of the risk of organ damage and death.

Once an individual is recovered, available evidence suggests they are likely to be immune to future chikungunya infections 

Diagnosis

Chikungunya virus may be detected directly in blood samples collected during the first week of illness using tests such as reverse transcriptase–polymerase chain reaction (RT–PCR).

WHO states that other tests can detect a person’s immune response to chikungunya virus infection. 

These are typically used after the first week of infection to test for antibodies to the virus. 

The antibody levels are typically detectable by the first week after illness onset and can still be detected for about two months.  

The return of Chikungunya

Deputy Manager of the Emergency Operations Centre in Mombasa, Fatma Ali, attributes the surge in infections to the ongoing rains, which have created ideal breeding conditions for mosquitoes. 

She emphasised the importance of community involvement in controlling the outbreak.

“It is our responsibility to ensure that our environment is clean by removing stagnant water, and this will reinforce the efforts that the county government is currently undertaking to control the disease,” Ali said. 

Residents have been urged to eliminate stagnant water around their homes, use mosquito repellents, wear protective clothing and utilise window and door screens to reduce mosquito exposure. 

Health officials have emphasised the importance of community cooperation in controlling the outbreak and preventing further spread of the disease.

Management and treatment

WHO states that there are currently two chikungunya vaccines that have received regulatory approvals in several countries and/or have been recommended for use in populations at risk.

The vaccines are, however, not yet widely available or in widespread use. 

WHO and external expert advisors are reviewing vaccine trial and post-marketing data in the context of global chikungunya epidemiology to inform possible recommendations for use.  

There is no specific antiviral treatment for chikungunya virus infections, but antipyretic and analgesic medications (such as paracetamol) for fever and pain can be used to alleviate these symptoms.

Severe symptoms and deaths from chikungunya are rare and usually occur in young babies or elderly people with other coexisting health problems.

Prevention and control

WHO proposes that the main method to reduce transmission of chikungunya is through control of the mosquito vectors and reduction of mosquito breeding sites. 

This requires mobilisation of communities, who are critical in reducing mosquito breeding sites through emptying and cleaning containers that contain water on a weekly basis, disposing of waste, and supporting local mosquito control programmes.

During outbreaks, insecticides may be sprayed to kill flying adult mosquitoes, applied to surfaces in and around containers where the mosquitoes land, and used to treat water in containers to kill the immature mosquito larvae. 

This may also be performed by health authorities as an emergency measure to control the mosquito population.

WHO advises people living in or visiting areas with chukungunya transmission to wear clothing that minimises skin exposure to the day-biting mosquitoes. 

Window and door screens should be used to prevent mosquitoes from entering homes. 

Repellents can be applied to exposed skin or clothing in strict accordance with product label instructions.

Repellents should contain DEET, IR3535 or icaridin. 

Insecticide-treated mosquito nets should be used against day-biting mosquitoes by persons who sleep during the daytime, for example, young children, sick patients or older people.

WHO is committed to supporting countries in the confirmation of outbreaks through its collaborating network of laboratories, providing technical support and guidance to countries for the effective management of mosquito-borne disease outbreaks.

The health organisation also reviews the development of new tools, including insecticide products and application technologies.