Experts warn deadly disease has returned with record-high cases — here's what you need to know

Health officials in Japan have sounded the alarm over the record-setting outbreak of a tick-borne disease that's already led to the deaths of more than 10 people in 2025. 

What's happening?

As reported by Kyodo News, as of mid-August, 135 people in Japan had been diagnosed with Severe Fever with Thrombocytopenia Syndrome, or SFTS, a potentially fatal tick-borne disease. This surpasses the previous record of 134 annual cases back in 2023.

A majority of the confirmed cases have been found to occur in the western part of the country, with Kochi Prefecture leading the way with at least 14. According to the Japan Institute for Health Security, of the 135 cases confirmed so far this year, SFTS has claimed the lives of more than 10 people in Japan.

The Ministry of Health, Labor, and Welfare has urged residents and visitors to take proper precautions while spending time outdoors. These include covering exposed skin by wearing long sleeves and pants to prevent tick bites, which is the primary route of infection. 

Why is a Severe Fever with Thrombocytopenia Syndrome outbreak concerning?

Ticks can be quite common in Japan, typically found in natural environments as well as in grassy areas of agricultural and recreational land. The regional activity of these parasitic arachnids has historically been highest from spring to fall. However, rising global temperatures, as well as related changes in the populations of potential host animals, could expand the seasons and habitats hospitable to ticks, thereby increasing the risk of infection.

Common symptoms of SFTS include fever, nausea, diarrhea, and vomiting. More severe cases can lead to internal bleeding, neurological symptoms, and multi-organ failure.

The disease's onset and high fatality rate of around 10 to 30 percent, according to Kyodo News, can prove to be a challenge for health care systems. However, early diagnosis and effective treatment, such as with antivirals, can potentially prevent the most serious complications.

What's being done about Severe Fever with Thrombocytopenia Syndrome?

Unfortunately, there are currently no vaccines to prevent SFTS infection in humans. However, researchers have been working on several candidates that are currently in development. This includes studies into viral vector and mRNA vaccines.

While SFTS vaccines have shown promise in animal models, further research is still needed to develop safe and effective options for clinical approval and widespread use.

In the meantime, a big-picture approach to reducing the spread of SFTS might address the tick population itself. Nurturing biodiversity might help keep tick numbers in check and slow the spread of disease by increasing the number of hosts that are incapable of transmitting it.

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Mitigating the rise in global temperatures through investments in the clean energy transition may also help reduce the portion of the year and the regions conducive to tick activity, limiting their presence.

On an individual level, prevention might go beyond covering exposed skin when outdoors to also include wearing tick repellents and thoroughly inspecting humans and pets for ticks.

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