New orthonairovirus explains a share of unexplained tick-borne fevers in China
A previously unknown tick-borne virus has been identified in China and linked to a flu-like illness marked by fever, fatigue, gastrointestinal complaints, thrombocytopenia, and abnormal liver enzymes. The virus, named Asian longhorned tick nairovirus or ALTNV, belongs to the orthonairovirus genus in the Nairoviridae family and appears to circulate in the same regions and the same tick species that spread a far more familiar threat: Dabie bandavirus, the agent of severe fever with thrombocytopenia syndrome, or SFTS.
The clinical value of the finding is immediate. For years, a substantial fraction of patients with symptoms suggestive of DBV infection have tested negative, leaving clinicians with a febrile illness, low platelets, and no pathogen to name. ALTNV now fills part of that diagnostic gap. In the study cohort, 10.4% of 3,163 patients tested positive for ALTNV by viral RNA or IgM antibodies, and the proportion rose to 15.1% among those who were negative for DBV. A virus that common cannot be dismissed as a laboratory curiosity.
Among patients infected only with ALTNV, fatigue dominated the presentation and was reported by 84%. Gastrointestinal symptoms were nearly as common, affecting 80%, while 38% developed thrombocytopenia and 36% had elevated aminotransferase concentrations. Those lab abnormalities fit the biologic pattern of a systemic viral infection that can disrupt endothelial integrity, injure the liver, and disturb hematologic function without necessarily progressing to catastrophic hemorrhagic disease. In these single-infection cases, recovery was complete.
A narrower bedside lesson emerges from the clinical phenotype itself: a patient with fever, GI symptoms, low platelets, and modest transaminase elevation in a tick-endemic region may not have SFTS alone.
Coinfection with DBV carried the sharpest clinical penalty
The most consequential signal in the study came from the 38 patients infected with both ALTNV and DBV. Coinfection did not merely add another virus to the lab report; it tracked with worse organ dysfunction. Respiratory symptoms were more frequent in the coinfected group than in patients infected only with DBV, affecting 61% versus 38%. Kidney impairment was also more common, affecting 84% versus 66%. Seven of the 38 coinfected patients died, a mortality rate of 18.4% in that subgroup.
Those outcomes matter because they suggest viral coexistence may amplify severity through overlapping inflammatory pathways or a heavier systemic viral burden. DBV already causes a potentially fatal hemorrhagic fever syndrome with a reported case-fatality rate of 10% to 30%, and the emergence of a second virus in the same ecological niche complicates triage in endemic regions. When two pathogens share a vector and geography, clinical pattern recognition becomes less reliable, and laboratory confirmation becomes more urgent.
The genetic data support ALTNV as a distinct virus rather than a minor variant. Sequence analysis placed it within orthonairoviruses, and its proteins shared less than 80% amino acid identity with those of other species in the genus. Laboratory work went further: human serum containing ALTNV RNA infected cultured cells, the virus was visualized with immunofluorescence, electron microscopy showed orthonairovirus-like particles, and replication was demonstrated in multiple cell types. The pathogen is real, viable, and biologically capable of infecting mammalian systems.
Asian longhorned ticks carried the virus across 15 provinces
The ecological findings explain how ALTNV can move silently through human populations. Researchers tested 47,428 ticks collected from 15 provinces and found ALTNV RNA in 1.3%. Prevalence was highest in Haemaphysalis longicornis, the Asian longhorned tick, where 1.8% of specimens were positive. That species is already recognized as an efficient vector for emerging tick-borne pathogens, and the experiments in this study showed that it could transmit ALTNV to mice.
The transmission data close the loop between field surveillance and clinical disease. A virus found in human febrile illness, recovered from ticks, propagated in cell culture, and transmitted in an animal model carries the signature of a true zoonotic pathogen, not a contaminant or incidental sequence. The public health implications are substantial in regions where SFTS is endemic and the same tick populations are feeding on both humans and animals.
Diagnostic separation will now matter in a very practical way. A patient who tests negative for DBV does not necessarily have a benign illness, and a patient with DBV may still be harboring a second pathogen that worsens organ injury. In settings where rapid molecular testing is limited, that overlap risks under-recognition of coinfection and may delay more intensive monitoring for respiratory failure, renal dysfunction, or other complications.
The study also reframes the broader burden of undiagnosed febrile illness in tick-endemic China. If ALTNV accounts for a meaningful share of cases previously labeled unexplained, then fever surveillance, tick testing, and diagnostic algorithms all need to expand beyond a single-virus framework. The next clinical question is not whether ALTNV exists; it is how often clinicians are missing it, how frequently it co-occurs with DBV, and whether early recognition changes outcomes in the sickest patients.