Scientists Discover New Orthonairovirus in Man Bitten by Tick in China

A case report published in the New England Journal of Medicine describes a previously unidentified orthonairovirus, dubbed wetland weed virus (WELV), in a man bitten by a tick in a wetland park in Inner Mongolia, China, in 2019.

After isolating the virus from the index patient, a team led by researchers from the Beijing Institute of Microbiology and Epidemiology conducted surveillance to determine the prevalence of WELV infection among hospitalized patients with fever and a history of tick bites.

The index patient was a 61-year-old man hospitalized in June 2019 after developing fever and multiple organ dysfunction following a tick bite five days earlier and whose ability to cause disease in mice was studied.

WELV, a member of the orthonairovirus genus of the Nairoviridae family, is most closely related to the tick-borne Hazara orthonairovirus genogroup, which includes Crimean-Congo hemorrhagic fever virus, the authors noted.

Virus detected in other patients, ticks, animals

Seventeen patients from four regions of China presented with nonspecific symptoms such as fever, dizziness, headache, malaise, muscle pain, arthritis and back pain and sometimes with petechiae (spots on the skin or mucous membranes due to capillary bleeding), localized swelling of the lymph nodes and neurological symptoms.

WELV was diagnosed by RT-PCR (reverse transcription polymerase chain reaction). The most common test results were leukopenia (low white blood cell count), thrombocytopenia (low blood platelet count), and increased levels of d-dimer (indicating blood clots) and lactate dehydrogenase (indicating tissue or organ damage).

Analysis of serum from eight recovered patients revealed a four-fold higher concentration of WELV-specific antibodies than those observed in samples collected during acute infection. A field survey found WELV RNA in five species of ticks, as well as in sheep, horses, pigs, and Transbaikalian zokors (a type of rodent) collected from northeastern China.

WELV virus isolated from the index patient and ticks showed cytopathic effects (causing structural changes in cells) in cells lining the human umbilical vein. Injection of the virus into the abdomen of mice and hamsters resulted in infection, brain damage, and death.

Researchers said the Haemaphysalis concinna tick can transmit WELV to an animal, which then passes it to its offspring through the ovaries.

“The initial symptoms of WELV infection are nonspecific disease, requiring differential diagnosis with other tick-borne diseases,” the researchers wrote. “Improved surveillance and detection of emerging orthonairoviruses will provide a better understanding of the impact of these viruses on human health.”