SFTS is a tick-borne disease with a fatality rate of 10–30%. Diagnosis currently takes several days, but a simple kit that can give a result in 15 minutes, like a flu test, is under development. With a treatment approved in 2024, early diagnosis has become key, and Japanese medical technology holds the potential to save lives.

What Is SFTS? Rising Cases and Spreading Infection Areas

Severe Fever with Thrombocytopenia Syndrome (SFTS) is an emerging infectious disease contracted through the bite of a tick carrying the SFTS virus. First reported in China in 2011, it saw its first patient confirmed in Japan in 2013.

The main symptoms are fever, gastrointestinal problems (vomiting, diarrhea, abdominal pain), a drop in platelets, and a drop in white blood cells; severe cases involve impaired consciousness and hemorrhagic symptoms. The fatality rate is 10–30% (about 27% in domestic epidemiological studies), extremely high for a domestic infectious disease.

In 2025, Japan reported 183 cases as of November 2 that year, a record high. Cases had previously been concentrated in western Japan, but in July 2025 the first case with a presumed infection site in the Kanto region was confirmed in Kanagawa, and in August the first in Hokkaido was confirmed in Sapporo. The health ministry now advises caution even in prefectures with no confirmed cases.

Update: reports have kept climbing in 2026. As of mid-June, the cumulative total stood at 72 cases, running ahead of the pace set in the record year of 2025.

Why Rapid Diagnosis Is Needed

At present, a confirmed SFTS diagnosis requires detecting the viral gene by RT-PCR, with testing done via public health centers at prefectural institutes of health or the Japan Institute for Health Security. The several days this process takes to yield results is a problem.

When the antiviral drug favipiravir (Avigan) was approved in June 2024 as the world's first therapeutic for SFTS, the importance of early diagnosis rose further. Studies show that the viral load at the start of treatment strongly affects the prognosis, and that early administration raises survival rates. Post-marketing clinical trials of the drug began in December 2024.

If a rapid diagnostic kit that gives results in about 15 to 30 minutes at the point of care, like a flu antigen test, reaches practical use, the wait before treatment shrinks to the length of a consultation.

Efforts to Develop a Rapid Diagnostic Kit

Led by the National Institute of Infectious Diseases (now the Japan Institute for Health Security), work has advanced on developing an ELISA to detect SFTS virus antigens and on refining quantitative gene-based PCR. With support from the Japan Agency for Medical Research and Development (AMED) and its program for developing innovative drugs against emerging and re-emerging infectious diseases, diagnostic-technology development at universities and research institutes is accelerating.

Developing a rapid diagnostic kit requires producing monoclonal antibodies specific to the SFTS virus. Developing high-quality antibodies that can accurately recognize the viral protein without cross-reacting with other viruses is the technical challenge.

Several research institutions, including Osaka University, are working on simple test kits based on immunochromatography, with research toward practical use in progress.

Significance for Public Health

Putting an SFTS rapid diagnostic kit into practical use would, first, enable an immediate response at the point of care. Being able to test and diagnose on the spot a patient with fever and gastrointestinal symptoms and a history of a tick bite would help start appropriate treatment early and prevent the disease from spreading.

Veterinary use is also expected. SFTS also infects dogs and cats, and cases of transmission from infected animals to humans have been reported. Rapid screening at animal hospitals could help prevent secondary infection of veterinary workers and pet owners.

Furthermore, being able to quickly identify infection areas and grasp the state of an outbreak would make epidemiological surveys more efficient and lead to more effective preventive measures.

The Outlook Ahead and the Importance of Prevention

Development of a rapid diagnostic kit is steadily advancing, but practical use is still some time off. For now, avoiding tick bites is the most important preventive measure.

Ticks become active from spring through autumn. When entering woods or grassy areas, wear long sleeves and long pants and avoid exposing skin. Check your whole body after returning home, and if a tick has attached itself, do not force it off but see a medical institution.

Tick control for pets is also important. Use tick-prevention medication regularly and brush pets after walks.

Now that SFTS is no longer a disease of western Japan alone, the speed of diagnosis is directly a question of survival. How are tick-borne infectious diseases being tackled in your country, and how are diagnostic technologies developing? We'd love to hear from you.

References