Yezo virus, a new disease that infects humans, discovered in Japan

Japanese researchers have identified a previously unknown virus that can infect humans and cause disease.

Named the Yezo virus, this new virus is transmitted by tick bites and causes a disease whose symptoms include fever and a reduction in blood platelets and white blood cells, which are responsible for fighting foreign substances and disease.

The Yezo virus was discovered when a 41-year-old man was admitted to hospital in 2019 complaining of fever and leg pain after being bitten by a tick while walking in a forest in Hokkaido .

He was released after being treated for two weeks. The man tested negative for all tick-borne viruses that were known at the time. The following year, another patient was admitted with similar symptoms after also being bitten by a tick.

Researchers at the University of Hokkaido, including the virologist from the university’s International Zoonoses Institute, Keita Matsuno, performed genetic analysis on blood samples from the two patients and discovered a new nairovirus. This category of virus is called the “Nairobi sheep virus” and includes the Crimean-Congo hemorrhagic fever virus, both also transmitted by tick bite.

The team continued to look for signs of the virus in blood samples from patients admitted to hospital with similar symptoms since 2014. They found traces of the Yezo virus in at least five other patients, all of whom had fevers. high blood platelets and white blood cells. These patients also showed signs of abnormal liver function.

“At least seven people have been infected with this new virus in Japan since 2014, but so far no deaths have been confirmed,” Matsuno said in a press release from Hokkaido University.

The team’s research is published in the journal Natural communications.

Naming the new virus Yezo, the historic Japanese name for the island of Hokkaido where the virus was first discovered, the team set out to search for its source.

Examining blood samples taken from wildlife over a 10-year period from 2010, researchers found traces of Yezo antibodies in raccoons and Hokkaido Sika deer, which are native to the region. . The team also found Yezo virus RNA in three major tick species across the island in northern Japan.

Matsuno added that while there are currently no deaths associated with Yezo, testing beyond Hokkaido and in hospitals in Japan is now of vital importance.

He said: “All the cases of Yezo virus infection that we know of so far have not turned into deaths, but it is very likely that the disease is beyond Hokkaido, so we have to urgently investigate its spread. “