Understanding Chikungunya Virus: Risks and Insights for Australia

The World Health Organization (WHO) has recently expressed alarm over a notable increase in cases of chikungunya, a viral infection transmitted by mosquitoes. This concern is particularly highlighted by outbreaks occurring in La Réunion and Mayotte, two islands located in the Indian Ocean. Following a significant epidemic in 2004-2005, these islands have reported over 47,500 confirmed cases and 12 fatalities between August 2024 and May 2025. Additionally, Mayotte recorded 116 cases from March to May 2025.

Chikungunya has been identified in more than 100 countries, with local transmission reported in regions across Africa, Asia, and Europe. With this backdrop, it is crucial to understand what chikungunya is, how it spreads, and the implications for Australia.

Chikungunya Symptoms

The primary symptoms of chikungunya include fever, severe joint pain, and swelling in the joints. Other common symptoms can consist of headaches, rashes, muscle pain, nausea, and fatigue. While the disease is rarely fatal, certain demographics, such as infants, older adults, and individuals with pre-existing health conditions, may experience more severe symptoms. Symptoms typically manifest within 3 to 7 days after a mosquito bite, but can take up to 12 days to appear. Although there is no specific treatment for chikungunya, pain management using medications like paracetamol is recommended. Most individuals recover within weeks, although some may continue to experience fatigue and joint pain for months or even years.

Transmission Mechanism

Chikungunya is spread by infected female mosquitoes. The transmission cycle begins when these mosquitoes bite a person whose blood contains the virus. Once infected, the mosquitoes can transmit the virus to others during subsequent bites. The two primary mosquito species responsible for chikungunya transmission are Aedes aegypti and Aedes albopictus. These species are easily distinguished by their black and white markings and are notorious for biting during the day, often targeting exposed skin, particularly around the ankles.

Global Distribution of Chikungunya

First identified in Tanzania in 1952, chikungunya outbreaks have predominantly occurred across Africa and Asia. Over the years, the virus has spread globally, affecting 119 countries and territories as of December 2024. The 2004-2005 epidemic marked the largest outbreak, originating from the Indian Ocean islands and eventually reaching India. The frequency and spread of chikungunya outbreaks have increased, partly due to the impacts of climate change, which has created favorable conditions for mosquito reproduction and adaptation.

Concerns for Australia

In Australia, Aedes aegypti mosquitoes have been present since the 1800s, with records of dengue outbreaks dating back to 1879. In contrast, Aedes albopictus was first documented in the Torres Strait in 2005. Currently, Aedes aegypti is widespread in various regions across Queensland, while Aedes albopictus is confined to the Torres Strait. Despite these mosquito populations, chikungunya transmission has not yet been documented within Australia. However, travelers returning from affected regions have reported cases, with 42 cases identified in 2023, 70 in 2024, and 90 in 2025, reflecting a potential rise in cases post-COVID travel restrictions.

As climate change continues to influence the distribution of mosquito species, the risk of local transmission in Australia may rise. Nonetheless, some evidence suggests that residents may have some level of immune protection from a closely related local virus, the Ross River virus.

Precautions for Travelers

Currently, there is no approved vaccine for chikungunya in Australia, although two vaccines are available in the United States. Travelers heading to regions where chikungunya is endemic should take preventive measures to avoid mosquito bites. Recommendations include wearing loose-fitting, light-colored clothing, applying insect repellent, closing windows, and using mosquito nets. These precautions can also mitigate the risk of contracting other mosquito-borne diseases, such as dengue fever. Anyone who travels to areas with chikungunya and experiences symptoms should seek medical attention promptly.