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Researchers in China have identified a previously unknown tick-borne virus, Asian longhorned tick nairovirus (ALTNV), in patients with unexplained illness and in ticks from 15 provinces. The study found ALTNV in 15.1% of patients who tested negative for the virus that causes severe fever with thrombocytopenia syndrome; the health effects of ALTNV alone and alongside that virus need further study.
Researchers in China have identified Asian longhorned tick nairovirus (ALTNV), a previously unknown tick-borne virus found in patients with unexplained illness and in ticks collected across 15 provinces. The study, reported in the New England Journal of Medicine, offers a possible explanation for some illnesses that resemble severe fever with thrombocytopenia syndrome (SFTS) but test negative for its known viral cause, Dabie bandavirus (DBV).
The research team, led by scientists at Beijing’s State Key Laboratory of Pathogen and Biosecurity, investigated patients treated at sentinel hospitals in regions where tick-borne viruses circulate. They used RNA sequencing and viral isolation to identify ALTNV. Genetic analyses placed it in the orthonairovirus genus, within the Nairoviridae family; its proteins shared less than 80% of their amino acids with those of other species in the genus. Laboratory tests also showed that it could grow in several cell types.
Of 3,163 patients included in the study, 10.4% tested positive for ALTNV through viral RNA or immunoglobulin M antibodies, which can indicate a recent infection. In the subset who tested negative for DBV, 15.1% tested positive for ALTNV. Among patients classified as infected only with ALTNV, fatigue was reported in 84%, gastrointestinal symptoms in 80%, thrombocytopenia in 38% and elevated aminotransferase concentrations in 36%. The researchers reported that these patients recovered completely.
The study also identified 38 patients with both viruses. Compared with patients infected only with DBV, those with both had respiratory symptoms more often (61% versus 38%) and kidney impairment more often (84% versus 66%). Seven coinfected patients died, or 18.4% of that group. These figures describe the study groups; they do not establish that ALTNV caused the additional complications or deaths.
A Possible Cause of DBV-Negative Illness
Identifying ALTNV gives clinicians and researchers another possible infection to investigate when patients in tick-endemic areas have compatible symptoms but test negative for DBV. The finding matters because DBV causes SFTS, a potentially deadly disease found across Asia. The source material gives its case-fatality rate as 10% to 30%, and the World Health Organization has identified it as a priority pathogen for research.
The reported overlap between ALTNV and DBV also complicates interpretation of symptoms and test results. The study found ALTNV RNA in 1.3% of 47,428 ticks collected across 15 provinces, with the highest reported prevalence—1.8%—in Haemaphysalis longicornis, or the Asian longhorned tick. Researchers said laboratory experiments showed this tick could transmit ALTNV to mice. Together, the findings support further investigation of the virus and improved diagnosis in areas where both viruses circulate.
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How Researchers Found ALTNV
The study began with a diagnostic gap: according to the source report, about 30% of patients whose symptoms suggested DBV infection tested negative for the virus. DBV is the known cause of SFTS, which can involve fever and low platelet counts. The researchers examined samples from people bitten by ticks and treated at hospitals in affected regions of China to look for other possible causes.
The team used sequencing, cell culture, immunofluorescence and electron microscopy to characterize the newly detected virus. It also examined thousands of ticks from multiple provinces. These methods provide evidence that ALTNV is a distinct virus and that it can infect humans and be carried by ticks; the study does not establish how widespread human infection is beyond the patients and locations examined.
“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 study authors
Questions About Risk and Severity
The findings do not establish how often ALTNV causes illness in the broader population, how severe infection may be across different groups, or whether ALTNV contributed to the worse outcomes recorded among coinfected patients. The study’s reported recovery among patients infected only with ALTNV is a finding from this patient group, not a guarantee about outcomes for all infections.
It is also unclear how well available tests identify ALTNV outside the study setting, whether the virus circulates beyond the regions sampled, and how frequently people are exposed. Tick positivity measures in this study describe the collected ticks; they do not by themselves establish a person’s chance of infection. Further surveillance and clinical research will be needed to answer these questions.
Further Testing and Surveillance
The study authors call for improved differential diagnosis between ALTNV and DBV in regions where SFTS is endemic. That will require additional work to assess diagnostic approaches and track infections over time. Monitoring both patients and tick populations could help researchers map where ALTNV circulates and clarify how often it is associated with illness.
Further studies can also examine outcomes in larger groups, including patients with coinfections, to clarify whether ALTNV changes the course of DBV illness. The source material does not specify a date for a next research milestone or a public health policy change.
Key Questions
What is ALTNV?
ALTNV is Asian longhorned tick nairovirus, a previously unknown virus in the orthonairovirus genus. Researchers detected it in patients with tick-associated illness and in ticks collected in China.
How many patients in the study tested positive?
Among 3,163 patients, 10.4% tested positive for ALTNV by viral RNA or immunoglobulin M antibodies. Among those who tested negative for DBV, 15.1% tested positive for ALTNV.
What symptoms were reported in ALTNV-only patients?
In patients classified as infected only with ALTNV, the study reported fatigue in 84%, gastrointestinal symptoms in 80%, thrombocytopenia in 38% and elevated aminotransferase concentrations in 36%. The researchers reported that these patients recovered completely.
Can Asian longhorned ticks transmit ALTNV?
The researchers reported laboratory evidence that Haemaphysalis longicornis, the Asian longhorned tick, could transmit ALTNV to mice. The study does not provide a measure of an individual person’s risk of infection.
Does ALTNV cause more severe disease when combined with DBV?
The study found more respiratory symptoms and kidney impairment among 38 coinfected patients than among patients infected only with DBV, and seven coinfected patients died. These observations do not prove that ALTNV caused the difference in complications or deaths.
Source: rss
