Objective:

To identify and characterize a previously unknown tick-borne virus in patients with fever and tick exposure in China.

Approach:

• Patient testing: Researchers used RNA sequencing to identify the virus in patients suspected of having SFTS who tested negative for Dabie bandavirus (DBV), then screened 3,163 patients with fever and recent tick exposure.
• Virus characterization: They analyzed the viral genome, cultured virus from patient serum, and used immunofluorescence and electron microscopy to confirm its identity.
• Tick investigation: Researchers tested 47,428 ticks from 15 provinces and conducted laboratory transmission experiments.

Key Findings:

• The virus, named Asian longhorned tick nairovirus (ALTNV), was classified as a distinct member of the Orthonairovirus genus.
• ALTNV RNA or immunoglobulin M antibodies were detected in 10.4% of the 3,163 patients; 15.1% of patients who tested negative for DBV had evidence of ALTNV infection.
• Among 56 patients infected only with ALTNV, fatigue was reported by 84%, gastrointestinal symptoms by 80%, thrombocytopenia occurred in 38%, and elevated aminotransferase levels in 36%. All recovered without reported lasting complications.
• Thirty-eight patients had both ALTNV and DBV. Respiratory symptoms and kidney impairment were more frequent than among patients with DBV alone; seven coinfected patients died. The study could not determine whether ALTNV contributed to greater severity.
• ALTNV RNA was detected in 1.29% of tested ticks, with the highest rate in Haemaphysalis longicornis (1.75%). Laboratory experiments showed this tick could transmit the virus to mice.

Interpretation:

The findings identify ALTNV as another potential cause of fever and thrombocytopenia after tick exposure. Because ALTNV and DBV can occur in the same regions and cause similar findings, the researchers noted that molecular and antibody testing may be needed to distinguish them.

Limitations:

• The study could not establish whether ALTNV contributed to greater disease severity in coinfected patients.
• Further assay validation and surveillance are needed to establish diagnostic performance and determine the virus’s geographic distribution.

Sources:

• The New England Journal of Medicine (as cited in the provided context)