Novel Virus Transmitted By Tick Bites In Japan; Causes Fever, Depletes Platelets, Leucocytes In Humans [Details]

If there is something that the COVID-19 pandemic has taught us, it is that there are several unknown viruses lurking around. And under the right circumstances, they can find a way to jump from animals to humans. Now, scientists have reported the discovery of a novel virus in Japan that is transmitted to human beings by ticks.

In a new study, researchers from Japan have described a previously unknown virus that was discovered in the Japanese island of Hokkaido. Named, Yezo virus, the pathogen is transmitted by tick bites. It results in a disease that is characterized by fever and a decrease in levels of blood platelets and leucocytes.

"At least seven people have been infected with this new virus in Japan since 2014, but, so far, no deaths have been confirmed," said Dr. Keita Matsuno, corresponding author of the study, in a statement. The findings were published in the journal Nature Communications.

A Novel Virus

The discovery was made when a 41-year-old man from Sapporo, Hokkaido was hospitalized in 2019. He had leg pain and fever after receiving a bite from an arthropod—suspected to be a tick—while walking through a local forest. The man was discharged two weeks later after being treated.

Interestingly, tests revealed that he was not infected with any of the viruses known to be borne by ticks in the region. The following year, another 59-year-old man was also presented to the hospital with similar symptoms after being bitten by an unknown insect, possibly by a tick.

Upon conducting genetic analysis of the viruses that had been isolated from the two patients' blood samples, an entirely new orthonairovirus, a genus of viruses within the family Nairoviridae, was discovered. Orthonairoviruses are known to cause febrile illnesses in humans and animals. The novel virus was named Yezo virus, after a Japanese name of historical significance in the Hokkaido region.

Family Nairoviridae consists of other pathogens such as the Crimean-Congo hemorrhagic fever virus. The Yezo virus was found to be most closely related to Sulina virus (identifiedin Ixodes ricinus ticks inRomania) and Tamdy virus (detected in Hyalomma asiaticum ticks in Uzbekistan). Recently, the Tamdy virus was reported to have caused cases of severe fever among humans in China.

Transmitted By Ticks

The team also examined blood samples that had been collected from patients in 2014. These patients had been hospitalized with similar symptoms after being bitten by ticks. Additional positive samples from five patients were found. Much like the first two patients, these older cases also had a fever and decreased levels of blood platelets and leucocytes. Also, they exhibited signs of abnormal liver function. Of the seven patients in total, four had been co-infected with Borrelia bacteria.

However, an important question still required answering—What is the actual source of the virus? In order to determine the potential source, the researchers screened samples obtained from wild animals in the region between 2010 and 2020. Antibodies against the virus were found in raccoons and shika deers in Hokkaido.

Additionally, the virus RNA was also discovered in three major species of ticks in the area: Haemaphysalis megaspinosa, Ixodes ovatus, and Ixodes persulcatus. "The Yezo virus seems to have established its distribution in Hokkaido, and it is highly likely that the virus causes the illness when it is transmitted to humans from animals via ticks," stated Dr. Matsuno. The virologist highlighted the need to study the virus further.

Dr. Matsuno, stressed, "All of the cases of Yezo virus infection we know of so far did not turn into fatalities, but it's very likely that the disease is found beyond Hokkaido, so we need to urgently investigate its spread." The authors of the study intend to trace the possible distribution of the Yezo virus nationwide in both animals and patients. They also asserted when patients complain of the characteristic symptoms, hospitals must test for the novel symptoms.