The world of tickborne diseases may have a new member. Scientists in China have identified a novel virus, dubbed the Wetland virus (WELV), that can infect humans and various animals. While only a handful of human cases have been documented so far, the virus appears capable of causing illness and potentially invading the brain.
This discovery, detailed in a recent New England Journal of Medicine publication, began with a 61-year-old man admitted to a Jinzhou hospital in June 2019. He presented with fever, headache, and multi-organ dysfunction. Significantly, he had been bitten by ticks five days prior while visiting a wetland park in Inner Mongolia, suggesting a link between the tick bite and his illness. The ineffectiveness of initial antibiotic treatment further pointed towards a viral infection.
Subsequent blood tests revealed a previously unknown viral agent. Genetic sequencing identified the virus as an orthonairovirus within the Nairoviridae family, closely related to other tickborne viruses like the Crimean-Congo hemorrhagic fever virus. This led to its designation as the Wetland virus, or WELV.
Following this initial case, researchers investigated the presence of WELV in both humans and animals near the presumed infection site. The virus was detected in low percentages of five tick species, most commonly in Haemaphysalis concinna ticks, known vectors of other tickborne diseases. WELV was also found in a small number of sheep, horses, pigs, and transbaikal zokors (a type of rodent). Retrospective analysis of blood samples from patients with fever following tick bites identified 20 potential WELV infections, with 17 cases where WELV was the sole tickborne pathogen detected.
Patients with suspected WELV infection presented with nonspecific symptoms such as fever, swollen lymph nodes, and dizziness. Some experienced tissue damage and blood clotting, while one patient even lapsed into a coma, exhibiting signs of neurological infection with elevated white blood cells in their spinal fluid. Fortunately, all identified patients recovered. However, experiments in mice showed that WELV can reach the brain and cause lethal infections.
Further research is crucial to fully understand WELV and the risk it poses to humans. One hypothesis suggests WELV can be transmitted through generations of Haemaphysalis concinna ticks via the ovaries of female ticks, a mechanism observed in other tickborne parasites. The presence of WELV antibodies in some dogs and cattle suggests a wider range of animal hosts. Additionally, WELV antibodies were found in a small percentage of seemingly healthy park rangers, indicating potential asymptomatic infections, similar to other tickborne diseases.
Much remains unknown about this newly discovered virus. The researchers emphasize the importance of enhanced surveillance and detection for emerging orthonairoviruses to better understand their impact on human health. The nonspecific nature of early WELV symptoms necessitates careful differential diagnosis from other tickborne illnesses.
In conclusion, the discovery of WELV highlights the evolving landscape of tickborne diseases and underscores the need for continued research and vigilance. While the current data suggests a potential threat, further investigation is needed to determine the true extent of the risk WELV poses to human populations.
