Japan is experiencing a surge in outdoor tick-borne infections this year, with experts warning that the number of cases could surpass the previous record high set in 2023. The National Institute of Infectious Diseases has reported approximately 90 cases of severe fever with thrombocytopenia syndrome (SFTS), a tick-borne infection, mainly in western Japan.
Ticks, which are parasitic arachnids found in outdoor spaces and are most active from spring to fall, are responsible for transmitting SFTS. Infectious disease experts have expressed concern about the expanding regions where these blood-sucking parasites are biting people. They urge caution to prevent the spread of the virus in unexpected places such as campgrounds and walking trails.
Tick-borne infectious diseases like scrub typhus and Japanese spotted fever have long been observed in Japan. Ticks can also transmit infections such as Lyme disease. However, recent years have seen an increase in cases of previously undetected tick-borne viruses affecting humans.
The first case of SFTS was reported in Yamaguchi Prefecture in 2013, followed by the Yezo virus in Hokkaido in 2021 and a fatal case of the Oz virus in Ibaraki Prefecture in 2023. SFTS is particularly concerning due to its high fatality rate of 27%. Symptoms typically appear after an incubation period of 6-14 days and include fever, vomiting, and diarrhea.
While most people contract these infections from ticks outdoors, there have been instances where transmission occurred from pets to humans or even between patients and their doctors. Experts emphasize paying special attention to areas near residential areas that border fields and mountains since ticks can be present even if individuals aren’t mountain climbing.
A study conducted by Kawasaki Medical School found that mountain climbing and highland trekking were common situations where people got bitten by ticks. However, cases also occurred during farming activities or while picking wild edible plants or tending gardens at home—particularly when wildlife like deer or wild boar were nearby.
Tick bites often go unnoticed initially since they don’t always cause pain immediately. It’s important not to forcibly remove a tick that is sucking blood because its head or mouth-parts may remain embedded under the skin after removal.
While progress has been made with therapeutic drugs like Avigan for treating tick bites associated with SFTS symptoms, prevention remains crucial according to Hanako Kurai from Shizuoka Cancer Center. She recommends wearing protective clothing such as long-sleeve tops, full-length trousers, hats, gloves when venturing into woodland areas along with using insect repellent and taking baths following outdoor activities.
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