Ticks are small blood-feeding arachnids that can carry a wide range of viruses, bacteria, and parasites. Because different pathogens can circulate in the same tick species, the illnesses they cause may overlap and be difficult to distinguish. Credit: Stock

Some unexplained cases of severe tick-related illness may have a previously overlooked cause.

A newly identified tick-borne virus may help explain why some patients in China develop symptoms resembling a dangerous hemorrhagic fever even though tests for the expected virus come back negative.

Researchers identified the virus as Asian longhorned tick nairovirus, or ALTNV. Among 3,163 patients tested in areas where tick-borne viruses circulate, 10.4% showed evidence of ALTNV infection. Among patients who tested negative for Dabie bandavirus, or DBV, 15.1% tested positive for ALTNV.

DBV causes severe fever with thrombocytopenia syndrome, or SFTS, a tick-borne disease found across Asia. Thrombocytopenia means a person has an abnormally low number of platelets, the blood cells that help with clotting. The disease has a reported fatality rate of 10% to 30%, and the World Health Organization lists DBV as a priority for research.

Negative DBV tests reveal another virus

Yet about 30% of patients with signs and symptoms suggesting DBV infection test negative for the virus. That unexplained group prompted researchers led by the State Key Laboratory of Pathogen and Biosecurity in Beijing to search for another possible cause.

The team collected samples from people who had been bitten by ticks and sought care at sentinel hospitals in parts of China where tick-borne viruses circulate. Using RNA sequencing and viral isolation, they identified ALTNV and determined that it belongs to a group of viruses known as orthonairoviruses within the Nairoviridae family.

Genetic analysis showed that ALTNV shared less than 80% amino acid similarity with other species in the same genus, supporting its identification as a distinct virus.

The researchers then tested whether ALTNV could reproduce in the laboratory. Serum from patients that contained ALTNV RNA produced viral growth in cultured cells. Immunofluorescence testing detected ALTNV viral antigens, while electron microscopy revealed features characteristic of orthonairoviruses. The virus was also able to replicate in several types of cells.

Coinfection brought more severe outcomes

The illnesses seen in patients differed depending on whether ALTNV occurred alone or together with DBV.

Among patients infected only with ALTNV, fatigue was the most common symptom, affecting 84%. Gastrointestinal problems occurred in 80%, while 38% developed thrombocytopenia and 36% had elevated aminotransferase levels, which can indicate inflammation or injury involving the liver or other tissues.

All patients with ALTNV infection alone recovered completely.

The picture was more concerning among people infected with both ALTNV and DBV. Among 38 coinfected patients, 61% developed respiratory symptoms, compared with 38% of patients infected with DBV alone. Kidney impairment occurred in 84% of coinfected patients, compared with 66% of those with DBV alone.

Seven of the 38 patients with both viruses died, representing 18.4% of the coinfected group.

Asian longhorned ticks carried ALTNV

The researchers also investigated how widely ALTNV was circulating among ticks. They detected ALTNV RNA in 1.3% of 47,428 ticks collected across 15 Chinese provinces.

The Asian longhorned tick, Haemaphysalis longicornis, had the highest prevalence, with 1.8% testing positive. Laboratory experiments also showed that this tick species could transmit ALTNV to mice, providing evidence that it can carry and spread the virus.

A shared tick complicates diagnosis

That overlap could complicate diagnosis. ALTNV and DBV circulate in the same regions, share a tick vector, and can produce overlapping symptoms, making it difficult to determine which infection a patient has based on symptoms alone.

“The cocirculation of ALTNV and DBV in the same areas, coupled with their shared tick vector, underscores the need for improved differential diagnosis between infections with these viruses in regions where SFTS is endemic,” the authors concluded.

Reference: “A Zoonotic Orthonairovirus from Febrile Patients in China” by Xiao-Ai Zhang, Bo Liu, Si-Qian Wu, Xin Yang, Ning Cui, Ling Lin, Xue-Jun Wang, Nan Li, Ming Chen, Ming-Da Hu, Jun Wu, Ellen Owen, Jonathan E. Owen, Li-Qun Fang and Wei Liu, 2 September 2026, New England Journal of Medicine.
DOI: 10.1056/NEJMc2602496

Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.