TOKYO — With a new tick-borne infection causing seven deaths this year, experts are advising people to dress carefully to avoid exposing their skin when ticks are active from spring to autumn.
The infection, called severe fever with thrombocytopenia syndrome (SFTS), is spread by a virus first identified in China in 2011, although SFTS cases occurred one after another beginning around 2009 in that country.
In Japan, a woman in Yamaguchi Prefecture who died last autumn was confirmed at the end of January as the first SFTS case in the country. Seven men and four women have come down with the disease as of April 10, all of whom are aged 50 or older and live in western Japan.
As the 11 patients had no record of overseas travel in recent years and the DNA of the viruses were somewhat different from those found in China, experts assume the virus has existed in Japan for some time.
The SFTS virus is carried by ixodid ticks — madani in Japanese — which thrive in rural areas.
When a person is bitten and becomes infected with the virus, they develop such symptoms as vomiting, stomach aches, diarrhea and a fever of 38 C or higher within two weeks.
Patients also show a decrease in their numbers of platelets and white blood cells.
Masayuki Saijyo, head of the Virology I Department at the National Institute of Infectious Diseases, said, “As early symptoms are similar to those of the common cold, it is difficult to confirm the infection.”
A diagnosis can only be made after testing for the virus, but even when confirmed, there is no cure at present. Patients must wait for a natural recovery, while being treated with intravenous drips.
Not all ixodid ticks carry the virus, and human-to-human infection is possible only through blood and bodily fluids. “There is no need to panic, even if you are bitten,” Saijyo stressed.
The key to preventing SFTS infection is to avoid being bitten. When near fields or in mountainous areas, people should wear long-sleeved shirts, trousers and hats or caps to minimize skin exposure.
To prevent ticks from reaching the skin, it is best to tie cuffs and hems with rubber bands and cover the neck with a towel or similar article.
Once a tick bites, it will continue to suck blood for a few days or even up to two weeks. Therefore, it is important to check your skin for ticks after returning from fields or mountains.
Ixodid ticks, which are black and three to four millimeters long, tend to bite soft parts of human skin, such as the neck, under arms and inside the navel.
If you find one on the skin, grasp it as close to the root of the bite as possible with tweezers and carefully and slowly remove it.
According to Junichi Aoki, a tick expert and an emeritus professor at Yokohama National University, a tick secretes a cementlike substance for a whole day to affix its mouth to the skin.
Therefore, it will become difficult to remove a tick 24 hours after being bitten.
Yoshio Hashimoto, an expert of tick-borne infections at Asahikawa-Kosei General Hospital in Hokkaido, advises people to visit a hospital and have a small section of skin around the bite removed when it is difficult to remove the tick on your own.
“If you try too hard, it may spread the pathogenic agent,” he warns.
Other major infectious diseases carried by ticks are Lyme disease, Japanese spotted fever and scrub typhus, which can cause red spots or high fever, but are all curable using antibiotics and other drugs.