Scientists in China Identify New Tick-Borne Virus Causing Flu-Like Illness

Scientists in China have identified a novel tick-borne virus that causes an influenza-like illness marked by fever, fatigue, gastrointestinal symptoms and abnormal lab findings. The team, led by researchers from the State Key Laboratory of Pathogen and Biosecurity in Beijing, designated the new orthonairovirus the Asian longhorned tick nairovirus (ALTNV). The discovery, published in the New England Journal of Medicine, grew out of a probe into why about 30% of patients with signs and symptoms of Dabie bandavirus (DBV) infection test negative for that tick-borne hemorrhagic fever.

DBV causes severe fever with thrombocytopenia syndrome (SFTS), a disease found throughout Asia with a case-fatality rate of 10% to 30% that the World Health Organization lists as a research priority. The researchers obtained samples from patients bitten by ticks at sentinel hospitals in parts of China where tick-borne viruses circulate, and identified the new virus through RNA sequencing and viral isolation. Phylogenomic analysis placed ALTNV in the family Nairoviridae, sharing under 80% of its amino acids with other species in its genus.

Of 3,163 patients tested, 10.4% were positive for ALTNV; among patients who tested negative for DBV, 15.1% tested positive for ALTNV. The most common symptoms in patients infected with ALTNV alone were fatigue (84%), gastrointestinal problems (80%), thrombocytopenia (38%) and elevated aminotransferase levels, indicating liver or tissue injury (36%); these patients recovered completely. Among 38 patients coinfected with both ALTNV and DBV, respiratory symptoms (61% versus 38%) and kidney impairment (84% versus 66%) were more common than in patients with DBV alone, and seven of the coinfected patients (18.4%) died.

ALTNV RNA was detected in 1.3% of 47,428 ticks collected across 15 provinces, with the highest prevalence, 1.8%, found in Haemaphysalis longicornis ticks. Experiments showed that H. longicornis ticks can transmit the virus to mice. The researchers said the cocirculation of ALTNV and DBV in the same areas, sharing the same tick vector, underscores the need for improved differential diagnosis between the two infections in regions where SFTS is endemic.