Novel zoonotic Langya virus identified in China

In a recent report published in The New England Journal of Medicine, scientists discuss their discovery of the novel Langya henipavirus (LayV) in eastern China. To date, a total of 36 patients have been diagnosed with acute LayV infection in the Shandong and Henan provinces.

Study: A Zoonotic Henipavirus in Febrile Patients in China. Image Credit: CI Photos / Shutterstock.com

The current outbreak

While monitoring febrile patients who reported recent contact with animals in eastern China, LayV infection was first identified through metagenomic analysis of a patient’s throat swab sample. This analysis revealed that the LayV genome consists of 18,402 nucleotides and is phylogenetically related to the Mojiang henipavirus that was previously discovered in southern China in 2014.

After their initial discovery of this infected patient, the researchers identified an additional 35 patients with acute LayV infection. Notably, 26 of these individuals were infected with LayV alone.

Of these 26 patients, 100% presented with fever, 54% with fatigue, 50% with anorexia and cough, 46% with myalgia, 38% with headache, and 35% with vomiting. Thrombocytopenia and leukopenia were reported in 35% of patients, whereas liver and kidney function were reported in 35% and 8% of these patients, respectively.

The researchers who identified the first LayV virus also surveyed 25 species of wild small animals as potential hosts for this virus. To this end, LayV ribonucleic acid (RNA) was identified in 27% of the surveyed shrews, thus suggesting that this animal is the most likely reservoir for this virus. Other domestic animals that were seropositive for LayV included 2% and 5% of surveyed goats and dogs, respectively.  

A review of other henipaviruses

Other notable viruses of the henipavirus genus include the Nipah virus (NiV) and Hendra virus (HeV). Both NiV and HeV are naturally found in Pteropus spp bats; however, their spillover into mammals ultimately led to their ability to infect human beings.

During a 1994 HeV outbreak, the infection initially presented with influenza-like symptoms following a seven to 16-day incubation period. Of the seven infected individuals, two recovered, and one developed pneumonitis and died from organ failure. The remaining three patients experienced encephalitic manifestations, including confusion, and ataxia, with fatal seizures reported in two patients.

NiV was first discovered in 1999 following an outbreak reported among both pigs and people in Malaysia and Singapore. Since then, several NiV outbreaks have been identified in Bangladesh, India, and Malaysia.

Whereas the Malaysia strain of NiV (NiV-M) is associated with a case fatality rate (CFR) of 40% and primarily causes neurological symptoms, the Bangladesh strain (NiV-B) typically causes severe respiratory distress and has a CFR of 90%.

NiV and HeV infections arise following exposure to infected human or animal secretions and respiratory droplets. Notably, previous NiV outbreaks in Bangladesh found that human-to-human transmission occurred among patients experiencing respiratory symptoms of the infection. Comparatively, both NiV-M and HeV outbreaks have not been associated with human-to-human transmission.

Approaches to mitigate LayV outbreak

In previous NiV outbreaks, public health officials have urged the widespread use of sensitive rapid diagnostic tests (RDTs) to quickly identify and isolate potentially infected individuals. Several preventative and non-pharmaceutical measures can also be implemented to effectively reduce the R₀ until medical countermeasures become available.

NiV and other henipaviruses are associated with high pathogenicity and, as a result, are considered to be pathogens of notable epidemic potential. Although there are no therapies currently available to treat henipavirus encephalitis, several broadly active antiviral therapeutics that target different RNA and DNA viruses could potentially be used against henipavirus infection. However, many of these drugs require additional pre-clinical and clinical investigation in order to determine their efficacy against henipaviruses.

Several monoclonal antibodies (mAbs) are also under development against henipaviruses. Thus, these agents could be used as both pre- and post-exposure prophylactic measures until a vaccine becomes available.

Conclusions

Since LayV was the only pathogen identified in a majority of the patients with acute LayV infection, the researchers are confident that LayV was the primary cause of their febrile illness. Notably, contact tracing of 15 people who interacted with nine LayV-infected patients did not reveal that human-to-human transmission occurred; however, the small sample size of the study does not eliminate the possibility that human-to-human transmission of this virus is possible.

Sentinel surveillance of similar febrile illnesses reported among people who recently interacted with shrews or other potential reservoirs of LayV is essential to better understand this human illness. Due to the sporadic and often unpredictable nature of henipavirus outbreaks, it is essential to isolate suspected cases of LayV infection and maintain open communication with public health agencies on new data as it becomes available.