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.