Fever from the fields

It has been confirmed that five people in Japan have died of severe fever associated with thrombocytopenia syndrome (SFTS), a virus infection believed to be transmitted by ticks. It’s possible that the number of deaths from the disease will increase. The central government needs to collect information on suspected cases from local governments and make efforts to establish an effective treatment for SFTS.

People also need to be aware that ticks transmit other diseases as well, such as Japanese scarlet fever, Lyme disease and rabbit fever. Trombiculid mites (tsutsugamushi) transmit scrub typhus. It is important for people to take utmost care to guard against bites from ticks, which live in fields and forests.

From around 2009, several hundred SFTS cases were reported in China. In 2011, a particular virus that causes the disease was identified. The disease has an incubation period of six days to two weeks and causes nausea, fever and diarrhea. It is characterized by a fall in the number of blood platelets and white blood cells. It can also cause subcutaneous bleeding and melena. The mortality rate in China was said to be about 12 percent.

A doctor who treated a woman in Yamaguchi Prefecture who died in the fall of 2012 noticed that her symptoms were similar to those of SFTS and sent her preserved blood to the National Institute of Infectious Diseases for a test. On Jan. 30, the health and welfare ministry announced that she had died of the disease.

By Feb. 26, it was confirmed that four men, from Ehime, Miyazaki, Hiroshima and Nagasaki prefectures respectively, also died of the disease. There was no indication that the victims had been bitten by ticks and the infection routes are not known. But it is logical to assume that mites could have been the source since the virus causing SFTS was found in mites in China.

The virus found in the five Japanese cases had similar gene arrangements but differed slightly from those found in China. The health and welfare ministry thinks that the virus is indigenous to Japan. There is the possibility that other people who were bitten by ticks and who suffered a high fever also were SFTS sufferers. It is important to collect relevant information to determine how many other SFTS sufferers there might be.

To reduce the chance of tick bites when walking in wooded, bushy terrain, skin exposure should be minimized by wearing long-sleeve shirts, pants tucked into socks, and shoes that fully cover the feet, as well as a hat and gloves. A towel wrapped around the neck can provide additional protection.

At present, no effective treatment or vaccination for SFTS exists. Only the symptoms can be treated. It is imperative that the central and local governments accumulate as much information on SFTS as possible as a basis for developing a treatment for the disease.