Newly discovered orthonairovirus is associated with human febrile illnesses

1. A newly found orthonairovirus, Wetland virus (WELV), was discovered to be pathogenic to humans, causing
febrile illnesses in northeastern China.

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

Evidence Rating Level: 2 (Good)

Study Rundown: Tickborne viral infections are associated with significant morbidity and mortality worldwide. The genus orthonairovirus comprises species of tickborne viruses that are responsible for febrile illnesses in humans. Despite the prevalence of viral illnesses transmitted by tick vectors, the maintenance of enzootic cycles is unclear, making it difficult to prevent and control these diseases. In 2019, a patient presented to a hospital in Liaoning, China, with fever and multiorgan dysfunction after a tick bite in a wetland park in Inner Mongolia. After sequencing the patient’s serum, it was revealed that the patient had an orthonairovirus, designated WELV. The present study identified febrile patients with a history of tick bites by conducting active hospital-based surveillance in China. Epidemiological investigations, animal sampling, and serological testing were also conducted to study the infectivity and pathogenicity of WELV. This study identified Haemaphysalis concinna as a possible vector for the WELV orthonairovirus. The virus was shown to be pathogenic in both human and animal models, which raised concerns about fever disease risk to the region.

Click here to read the study in NEJM

In-Depth [epidemiological study]: This study identified and characterized the novel orthonoairovirus, WELV, in northeastern China by investigating its epidemiology, transmission, and pathogenicity. Active surveillance was performed in four medical facilities in northeast China, where patients who had developed acute fever within one month after a tick bite were identified. These patients underwent screening for WELV via molecular and serological testing on blood and serum samples. Laboratory testing was also conducted to isolate WELV via reverse transcriptase polymerase chain reaction (RT-PCR) from ticks, tissue samples from wild animals, and serum samples from domestic animal and human patients (n=682). To assess the pathogenicity of WELV, viral load and clinical signs were monitored after in vivo experimental infections were produced in mice and hamsters. Viral transmission was also assessed by conducting transmission studies with the Haemaphysalis concinna tick. Results from this study identified WELV as a tickborne virus from the orthonairovirus genus in the Nairoviride family. Seventeen patients from northeastern China were identified with acute WELV infection. These patients presented with symptoms such as fever, dizziness, headache, and myalgia. Laboratory findings from these patients revealed leukopenia, thrombocytopenia, and elevated D dimer and lactate dehydrogenase levels. The WELV RNA was detected in five tick species and horses, pigs, and sheep sampled in northeastern China. In vivo, infection of some strains of mice by WELV resulted in death. The Haemaphysalis concinna tick was identified as a possible vector for WELV. The virus was shown to be pathogenic in both human and animal models, raising concerns about health impacts in northeastern China.

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