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 and molecular and antibody tests to investigate patients with suspected SFTS who tested negative for Dabie bandavirus (DBV), then screened 3,163 patients with fever and recent tick exposure.
• Virus characterization: They analyzed the virus’s genome, cultured it 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 in mice.

Key Findings:

• The newly identified 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 screened; 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.
• Among 38 patients coinfected with ALTNV and DBV, respiratory symptoms and kidney impairment were more frequent than among patients with DBV alone. Seven coinfected patients died, but the study could not determine whether ALTNV contributed to greater severity.
• ALTNV RNA was detected in 1.29% of ticks tested. The highest rate was 1.75% in Haemaphysalis longicornis, which transmitted the virus to mice in laboratory experiments.

Interpretation:

The findings identify ALTNV as another potential cause of fever and thrombocytopenia after tick exposure. Because ALTNV and DBV occur in the same regions and can cause similar findings, the researchers note 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.

Conclusion:

The findings were reported in The New England Journal of Medicine.

Sources:

• Article context; The New England Journal of Medicine study