Yezo virus is a new germ transmitted by ticks, according to Japanese doctors

Another day, another germ to fear. Scientists in Japan say they have shown that a previously unknown virus transmitted by ticks has been making people sick in the country since at least 2014. The Yezo virus, as it was named by its discoverers, is believed to be causing a drop in white blood cells. and platelet count as well as fever in its victims, similar to other tick-borne illnesses.

In a paper published last month in Nature Communications, researchers laid out their case for Yezo being a new human virus. According to the report, Yezo’s first known occurrence was in a 41-year-old man who was admitted to their hospital in Sapporo, Japan in mid-May 2019 with a high fever, loss of appetite, and lower limb pain in both. sides.

Symptoms started four days after visiting a nearby forest and three days after finding a tick attached to his right abdomen. Tests showed the man had low levels of white blood cells and platelets, the component of the blood that helps prevent or stop bleeding through clotting. Doctors assumed he had a tick-borne illness and gave him various antibiotics. Over the course of 19 days, 15 of which were in hospital, he gradually recovered and his symptoms disappeared. But during those days, tests failed to identify evidence of infection with a known tick-borne disease, including Lyme disease, tularemia and relapsing fever.

A little over a year later, in July 2020, doctors encountered another patient with similar symptoms. He had visited two hospitals before seeing them, but had also recovered successfully.

Eventually, say the authors, they were able to identify traces of the same unknown virus in the blood of the two patients. From the blood of the second patient, they claimed to have recovered enough virus to develop it fully intact in the lab and in mice. And finally, from these samples, they were able to genetically identify the mysterious bug as belonging to a family of viruses all spread by ticks, called orthonairoviruses. They decided to call it tentatively Yezo virus (YEZV), in reference to the historical name of Hokkaido, the largest island where it was first found.

Proving that a newly discovered virus can be transmitted and cause disease in humans, however, requires several sources of evidence, which the authors say they have collected.

For example, they say they have found antibodies to Yezo in the Hokkaido fauna and in three of the main tick species known to inhabit the area. More importantly, they also claim to have found evidence of Yezo infection in preserved blood samples from at least five other people in the area suspected of having a tick-borne illness, dating back to 2014. These patients, like the first two, appeared to develop fever and low platelet counts, while the blood of four patients overall exhibited levels of Yezo antibodies that became detectable as they recovered, which one expects from an acute infection. Interestingly, four of these patients also exhibited signs of Lyme disease, suggesting that they may have been co-infected with both germs. (Unfortunately, tick-borne co-infections are not rare).

“In this work, we demonstrate that YEZV is most likely the pathogen responsible for febrile illness, representing the first report of an endemic infection associated with an orthonairovirus potentially transmitted by ticks in Japan,” the authors wrote.

It will still take independent verification by other scientists before Yezo is considered the real deal. But the authors suspect it might be more widespread than what is currently documented, and they are pushing for more research to be done on it as soon as possible.

“Not all cases of Yezo virus infection that we know of so far have turned into death, but it is very likely that the disease is beyond Hokkaido, so we urgently need to investigate on its spread, ”said study author Keita Matsuno, a virologist. at the International Institute for Control of Zoonoses at the University of Hokkaido, in a declaration of the University.