Chikungunya virus in China

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A seasoned virologist with extensive experience working with insect-borne viruses and the diseases they cause, Roger is cross-appointed between the GSU at the Sanger Institute, the London School of Hygiene and Tropical Medicine, and the World Health Organization (WHO) Collaborating Centre for Virus Research & Reference. Working at the intersection of science and global public health, he is ideally placed to explain the implications of this outbreak.

Emphasising the need for continued surveillance and the useful insights that come from integrating genomic evidence with other forms of data, he stressed that the risk in the UK remains low.

“The chikungunya outbreak in China is a timely reminder of the growing risks posed by vector-borne viruses in an era of climate change, global mobility and shifting mosquito ecology.”

Professor Roger Hewson
Virus Surveillance Lead, Genomic Surveillance Unit at the Sanger Institute

A significant outbreak of chikungunya virus (CHIKV) is currently ongoing in Guangdong province, China, with over 8,000 confirmed cases reported in recent weeks. This represents the largest documented outbreak of CHIKV in China and has prompted aggressive containment measures, including quarantines, drone-based fogging and legal enforcement of mosquito control efforts. CHIKV is a mosquito-borne virus that usually causes acute, self-limiting illness but can also lead to prolonged joint pain and, in some cases, severe complications in the eyes and brain.

The outbreak in Foshan and surrounding areas of Guangdong province has unfolded rapidly and at a scale unprecedented for China. Authorities have responded with containment strategies reminiscent of COVID-19 measures, including household-level inspections, enforced bed-netting and fines for non-compliance with mosquito control. Unlike previous imported or isolated cases, this outbreak involves sustained local transmission, reflecting both increased environmental suitability for Aedes mosquitoes and a lack of population immunity. The scale and speed of spread of the virus mark it as a notable public health event in East Asia.

CHIKV infection typically presents with high fever, intense joint and muscle pain, rash, headache and fatigue. While many recover within a week, joint pain can persist for weeks, months, or even years in some individuals, mimicking conditions like rheumatoid arthritis.

Older adults, infants, pregnant individuals and those with underlying health conditions are more likely to experience severe or prolonged illness and a minority may develop neurological or vision complications. Importantly, many cases are asymptomatic or mild, allowing undetected individuals to contribute to transmission when they are bitten by infected mosquitoes.

CHIKV is transmitted via the bites of infected Aedes aegypti and Aedes albopictus mosquitoes, both of which are active during the daytime and breed in small pools of standing water. The virus is not spread directly between people. In this outbreak, Aedes albopictus is likely to be an important driver of transmission (although this is not currently confirmed). This mosquito has adapted to cooler climates and urban environments, making it a key vector for spread of the virus in subtropical regions like Guangdong.

Yes. CHIKV is already listed by the WHO and CEPI as a priority pathogen for vaccine development. It has demonstrated an ability to cause explosive outbreaks and is continuing to adapt genetically for more efficient spread by Aedes mosquitoes. With expanding global travel and a warming climate, new regions, particularly in Southern Europe and South America, are becoming suitable for transmission. The current outbreak in southern China highlights how densely populated, previously unaffected areas may become vulnerable. Pandemic potential is amplified by the absence of pre-existing immunity in these populations and the difficulty in rapidly controlling mosquito-borne outbreaks.

At present, the risk of local CHIKV transmission within the UK is considered to be very low, as the key mosquito species that carry the virus are not widely established in the UK. However, the risk to UK travellers visiting southern China is tangible. Travellers should take standard precautions to avoid mosquito bites, including using insect repellents, wearing long sleeves and trousers during the day and staying in screened or air-conditioned accommodation. There are no formal travel restrictions in place, but the outbreak warrants attention from clinicians and public health authorities, particularly in relation to returning travellers who develop a fever.

Two CHIKV vaccines have been approved for use in the UK: IXCHIQ and Vimkunya.

IXCHIQ is a single-dose live attenuated vaccine approved for immunocompetent adults aged 18 to 59, but its use is currently restricted in those aged 65 and above due to safety concerns raised by the Commission on Human Medicines.

Vimkunya, meanwhile, is approved for individuals aged 12 and older. Although not yet in widespread use, these vaccines may be available through specialist travel health services.

Several other vaccines, including virus-like particle, mRNA-based, and measles-vectored platforms, are under active development.

Vaccination is recommended for individuals at higher risk travelling to outbreak areas, particularly older adults, immunocompromised persons and pregnant individuals, though availability and eligibility criteria should be checked in advance.

Genomic surveillance can provide useful insights during chikungunya outbreaks by revealing how the virus is spreading and evolving. By sequencing viral genomes from patients and mosquitoes, scientists can determine whether the outbreak in China is the result of a local emergence or an imported strain. This would enable tracking of how the virus is spreading through the population. It also allows detection of key mutations, such as those that might improve transmission by mosquitoes, which may signal changes in the virus's behaviour or its ability to establish in new regions. This information supports timely public health decisions, guides mosquito control efforts and ensures vaccines remain effective against circulating strains. Taken together, viral genomic information provides essential insights into outbreak dynamics, but a more comprehensive understanding of transmission also requires parallel surveillance of mosquito populations.

Genomic surveillance of mosquitoes can also enhance our understanding and control of chikungunya outbreaks. By sequencing the genomes of local Aedes populations, scientists can identify which species and lineages are circulating, assess their ability to transmit disease — also known as vector competence — and determine whether they are carrying CHIKV or indeed other viruses. Previous work on CHIKV has shown that mutations like E1-A226V in one of CHIKV’s envelope glycoproteins (E1), can significantly increase transmission efficiency in Aedes albopictus. It’s also shown that mosquito vector competence varies depending on genetic background and environmental conditions, such as temperature. This broadens the ecological risk, as European populations of Ae. albopictus can sustain CHIKV transmission even at cooler temperatures. Genomic data can also reveal insecticide resistance markers or shifts in mosquito feeding behaviour that may compromise control strategies.

Developing and maintaining the capability to carry out such integrated mosquito and virus genomic surveillance is increasingly important for anticipating and responding to future vector-borne disease threats.

In summary, the chikungunya outbreak in China is a timely reminder of the growing risks posed by vector-borne viruses in an era of climate change, global mobility and shifting mosquito ecology. Although the virus is unlikely to spread within the UK under current conditions, travellers to southern China may be exposed and should take appropriate precautions to prevent mosquito bites. The recent authorisation of CHIKV vaccines in the UK offers new tools for prevention, particularly for vulnerable individuals. With no antiviral treatments and unpredictable outbreak dynamics, ongoing genomic surveillance, vaccine accessibility, and mosquito control remain essential to mitigating the threat posed by this increasingly global virus.