The newly discovered orthonairovirus is associated with febrile illnesses in humans

1. A newly discovered orthonairovirus, wetland virus (WELV), has been found to be pathogenic to humans and causes
Febrile illnesses in northeast China.

2. WELV has been detected in various animal species and ticks, suggesting that the tick Haemaphysalis concinna may be the vector that transmits the infection.

Evidence assessment level: 2 (Good)

Study overview: Tick-borne viral infections are associated with significant morbidity and mortality worldwide. The genus Orthonairovirus includes species of tick-borne viruses responsible for febrile illnesses in humans. Despite the prevalence of viral diseases transmitted by tick vectors, the maintenance of enzootic cycles is unclear, making the prevention and control of these diseases difficult. In 2019, a patient presented to a hospital in Liaoning, China, with fever and multiorgan dysfunction following a tick bite in a wetland park in Inner Mongolia. After sequencing the patient's serum, it was determined that the patient had an orthonairovirus called WELV. The present study identified febrile patients with a history of tick bites through active hospital surveillance in China. Epidemiological studies, animal samples and serological tests were also carried out to investigate the infectivity and pathogenicity of WELV. This study identified Haemaphysalis concinna as a possible vector for WELV orthnairovirus. The virus was found to be pathogenic in both human and animal models, raising concerns about the risk of febrile illness in the region.

Click here to read the study in NEJM

Detailed [epidemiological study]: This study identified and characterized the novel orthonoairovirus WELV in northeast China by investigating its epidemiology, transmission and pathogenicity. Active surveillance was conducted in four medical institutions in northeast China, identifying patients who developed acute fever within a month of a tick bite. These patients were screened for WELV using molecular and serologic testing on blood and serum samples. Laboratory testing was also performed to isolate WELV from ticks, tissue samples from wild animals, and serum samples from domestic animals and human patients using reverse transcriptase-polymerase chain reaction (RT-PCR) (n=682). To assess the pathogenicity of WELV, viral load and clinical symptoms were monitored after experimental infections were induced in mice and hamsters in vivo. Viral transmission was also assessed by conducting transmission studies with the Haemaphysalis concinna tick. The results of this study identified WELV as a tick-borne virus from the genus Orthonairovirus in the Nairoviride family. Acute WELV infection was detected in 17 patients from northeast China. These patients presented symptoms such as fever, dizziness, headache and myalgia. Laboratory findings in these patients showed leukopenia, thrombocytopenia, and elevated D-dimer and lactate dehydrogenase levels. WELV RNA was detected in five tick species as well as horses, pigs and sheep in northeast China. In vivo, infection of some strains of mice with WELV resulted in death. The tick Haemaphysalis concinna was identified as a possible vector for WELV. The virus was found to be pathogenic in both human and animal models, raising concerns about health effects in northeast China.

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