Does Langya virus pose a spillover threat?

By Dr. Liji Thomas, MDReviewed by Benedette Cuffari, M.Sc.Aug 30 2022

The coronavirus disease 2019 (COVID-19) pandemic has brought attention to the recurring threat of zoonotic viruses as potential sources of future pandemic diseases. Such pathogens initially leap across the species boundary, ultimately becoming infectious and capable of replicating within humans rather than their original or reservoir animal species.

Study: Spillover Zoonotic 'Langya Virus': Is It a Matter of Concern? Image Credit: CI Photos / Shutterstock.com

Introduction

Almost 75% of newly emerging infections are zoonotic. This phenomenon is largely due to the intrusion of human activity and residences into wildlife habitats, as well as alterations in habitats caused by environmental and climate change. Notably, climate change alters the way host species interact with the pathogen.

The transmission of pathogens from animals to humans has recently been reported in a henipavirus called the Langya virus (LayV) in Eastern China. The discovery of this virus was made amid surveillance efforts initiated during the COVID-19 pandemic and the current monkeypox virus outbreak in non-endemic nations.

LayV belongs to the same family as the Hendra and Nipah viruses.

The severity of Nipah infections can range from asymptomatic to lethal respiratory infection, with encephalitis reported in some severe cases. The Nipah virus fatality rate ranges from 40% to 75%.

Nipah virus has also been shown to spread between contacts in hospitalized cases, which is unlike the Hendra virus. To date, little is known about LayV.

In a Letter to the Editor published in the journal Veterinary Quarterly, researchers assess the potential impact of LayV, its current risk, and what measures might help to contain this virus and, as a result, reduce the size of the outbreak.

About LayV

LayV is a henipavirus belonging to the Paramyxoviridae family and consists of a single-stranded ribonucleic acid (RNA) genome. Aside from Nipah and Hendra viruses, both of which cause severe respiratory infections with lethal potential, other known henipaviruses include Cedar, Mojiang, and Ghanaian bat viruses, the latter of which is now called Kumasi virus (KV). Only Cedar and Mojian viruses have been shown to infect humans.

LayV is most closely related to the Mojiang virus, which is a paramyxovirus often carried by rats. In 2012, the Mojiang virus was suspected to be the cause of lethal pneumonia in three miners in southern China’s Yunnan province. Their blood samples were negative for Nipah, Ebola, and the severe acute respiratory syndrome coronavirus (SARS-CoV).

The ultimate death of these miners led to the identification of this virus in the buff-breasted rat (Rattus flavipectus), which is native to Southeast Asia and China. The Mojiang virus does not share a common mechanism of cell entry with either the Hendra or Nipah viruses.

LayV was first identified in two northeastern Chinese provinces in 2018. However, in August 2022, LayV was formally recognized by scientists in their report published in the New England Journal of Medicine.

The host

LayV is thought to be carried by shrews, with its RNA having been found in over 25% of nearly 260 shrews. Thus, scientists believe that shrews may be the reservoir species that act as a direct or indirect vector for human transmission. About 5% and 2% of dogs and goats, respectively, have also tested positive for LayV.

Only 35 cases of human infection have been reported since 2018, none of which appear to be due to human-to-human infection. The likely route of transmission is from rodent-like mammals to humans, with most infections reported in farmers and factory staff.

No human-to-human contact has been discovered; however, the small size of the initial study demands further research before this can be conclusively ruled out. This is urgently needed, as the high prevalence of LayV in shrews indicates that if human-to-human spread occurs readily, it would lead to infection in almost 100% of the population.

The illness

LayV infection appears to present with non-specific symptoms like fever, cough, fatigue, loss of appetite, and muscle aches. Almost all cases presented with fever, 26 of which did not test positive for any other pathogen except for LayV. While several individuals have been infected by LayV, none have died due to this infection.

Possible treatments might include ribavirin or chloroquine, both of which are active against Hendra and Nipah viruses. New vaccines that can be distributed to high-risk areas are warranted.  

Implications

There remains a lack of research available to fully determine the threat posed by LayV.

Due to the devastating effects of climate change, zoonotic spillover events are becoming more common. In fact, previous research indicates that half of modern human infections are due to climate change-related events.

Thus, continuing surveillance is needed to quickly identify such spillovers early enough to prevent worldwide disasters like the COVID-19 pandemic. This must be done in a collaborative fashion while making all data available to scientists and public health officials.