Credit WHO
#17,020
Six weeks ago, in NEJM: A Novel Henipavirus With Human Spillover In China, we looked at initial reports of A Novel Henipavirus With Human Spillover In China, which researchers described as a phylogenetically distinct henipavirus - dubbed Langya henipavirus (LayV) - which they isolated from the throats of 35 fever patients who reported recent animal exposure.
Henipaviruses - of which Nipah and Hendra are the best known - belong to the Paramyxoviridae family of viruses, and have sparked a number of deadly spillovers into humans - and epidemics - across South East and Central Asia - and to a lesser extent Australia - over the past 25 years.
While normally associated with Fruit bats, we don't really know the full extent of their host range. We do know that in addition to bats, henipaviruses can infect humans, horses, and swine and can produce severe, often, fatal, illness.
Nipah - which has been the deadliest henipavirus to date - was only identified 25 years ago after an outbreak in Malaysia, which spread from bat to pigs - and then from pigs to humans - eventually infecting at least 265 people, killing 105 (see Lessons from the Nipah virus outbreak in Malaysia).
Characteristics of Nipah virus that increase its risk of becoming a global pandemic include: humans are already susceptible; many strains are capable of limited person-to-person transmission; as an RNA virus, it has an exceptionally high rate of mutation: and that if a human-adapted strain were to infect communities in South Asia, high population densities and global interconnectedness would rapidly spread the infection.
So, when news of a newly discovered zoonotic henipavirus was announced from China's eastern Shandong and Henan provinces, researchers and public health officials took notice.
Although the virus was found in 35 patients - all exhibiting a range of symptoms (fever, cough, fatigue, anorexia, leukopenia, and for some - liver or renal damage) - they haven't fully established a causal relationship between the viral infection and the disease, although it is strongly suspected.The initial report indicated - in addition to the confirmed human infections - that genetic testing of 25 animals found low levels of the virus in dogs (5%) and goats (2%), but much higher levels (27%) in shrews, which they suspect may be the reservoir host for this virus.
Given the events of the past 3 years, the discovery of another zoonotic virus in China has raised eyebrows, but there are undoubtedly many such viruses around the world. They occasionally spillover into humans, but (so far, at least), but only rarely do they have what it takes to spark a wider epidemic.
Some of the `lesser' novel viruses we've seen emerge over the past decade include:
Nosocomial Outbreak of SFTS Among Healthcare Workers in a Single Hospital in Daegu, Korea
Alaska Reports 3rd & 4th Case of A Novel Zoonotic Orthopoxvirus (Alaskapox) Near Fairbanks
EID Journal: Bourbon Virus in Wild and Domestic Animals, Missouri, USA, 2012–2013
EID Journal: Novel Poxvirus in Proliferative Lesions of Wild Rodents in East-Central Texas, USA
EID Journal: Influenza A(H6N1) In Dogs, Taiwan
Langya virus outbreak in China, 2022: Are we on the verge of welcoming a new pandemic?
Abstract
Langya virus is a zoonotic virus that belongs to the family Paramyxoviridae; genus Henipavirus with close relation to species; HeV and NiV. Its animal reservoir is shrews, others being domestic goats and dogs. Its symptoms can range from mild respiratory illness to fatal encephalitis.
The first case of the Langya virus emerged in China after its detection in a 53-year-old farmer who presented with febrile illness and had a history of animal contact. Later a study that recruited 35 febrile patients from 3 different hospitals of China detected the Langya virus genome in 26 patients declaring it an outbreak in China. Most of these patients were farmers; however, these cases did not show any trace of linkage among each other that could have led to more understanding of the exact mechanism of transmission among humans.
Like many other nations, China faces climatic crises that favor zoonotic spillovers. Studies are still going on to formulate ways to detect Langya virus. Currently, the only management available involves supportive care. Trials in laboratories have shown efficacious results with ribavirin. Community-based surveillance strategies and extensive research on vaccine development are the need of the hour to contain this disease from becoming a global pandemic.
(SNIP)
Dear Editor
Langya henipavirus (LayV) is an emerging pathogen belonging to the genus Henipavirus. It has relation to Hendra (HeV) and Nipah (NiV) species which are highly fatal1 and notorious for infecting humans and animals both. LayV belongs to the Paramyxovridae family.2 Zoonotic RNA of HeV has its origin from Australia and infects horses, while NiV has caused multiple outbreaks in South East Asia.3 LayV genome comprises of 18,402 nucleotides.4 It is a zoonotic pathogen; the positivity rate of LayV antibodies was found in 5% of dogs and 2% of goats.3 LayV RNA was isolated from 27% of 267 shrews (small mole-like animals),2 suggesting shrews are a possible reservoir for human transmission. However, the exact mechanism of its spread to humans is still unknown. Symptoms range from respiratory nature presenting with fever, fatigue, and cough2 to fatal encephalitis.
The first ever hint of LayV emerged in China when a 53-year-old farmer visited a hospital in Shandong in December 2018 with a predominant complaint of fever and a history of contact with animals within a month of symptom onset.2 LayV genome, related to HeV and NiV was detected in throat swabs of the aforementioned farmer upon enrollment in a screening study for zoonotic diseases. This study included 35 patients from 3 hospitals of Shandong and Henan who were suspicious of having LayV.5 Results from this study detected the LayV genome in 26 out of 35 recruited febrile patients, suggesting LayV as the sole cause of illness in these patients.6
Out of these 26 cases, all had a fever, 50% had a cough, 46% reported myalgia, 35% had a headache, and vomiting was present in 35% of them. The blood profile of 26 patients was also evaluated, which revealed 54% of patients with leukopenia, 35% showed thrombocytopenia, and some had hepatic function impairment.7 The effect of LayV on immunity needs to be addressed as it can open gates toward many more opportunistic pathogens.
Most of these patients were farmers; some were factory employees,3 which can hint toward LayV being a febrile illness with some relation to farmers' environmental exposure. When the contact of 9 patients having close contact with 15 family members was traced, close contact transmission could not be proved,3 which suggests sporadic transmission in humans; however, the sample size was too small. No clusters of cases have shown up from the same family or geographical propinquity, indicating ambiguity about its spread to humans2 raising curiosity on how these cases were exactly exposed to LayV. None of all patients infected with LayV in China have been reported dead, so fatality is still doubtful7; however, NiV species carry a 90% possibility of death.7
The primary reservoir for LayV is shrews; however, many other animal hosts indicate its capability to evolve over time, just like COVID-19, so the more the number of hosts, the more the chances for LayV to adapt.
The threat is that we are unaware of what these adaptations might be and what might these adaptations do and thus possess the potential to unlock several means of global spread. However, we can take a breath of relief as no human-to-human transmission has yet been reported.8 So, there are high chances that LayV cannot become a pandemic in contrast to COVID 19. Living in a world of pandemics like COVID-19 and monkeypox, we must keep close eyes on emerging infectious diseases like LayV.
As little is known about the pathogenicity of LayV, further research should focus more on knowledge of viron to reach the root mechanism behind its infectivity and spread. Strategies for community-based surveillance should be developed to combat the LayV outbreak. Investigations should be carried out to know more about the exact mode of transmission; help can be sought from already discovered cousin viruses, HeV and NiV, to know more about LayV, its structure, and mode of spread to detect and promptly contain the disease timely.
Planning of outbreak management strategies is the need of the hour as the emergence of LayV in eastern China suggests how effortlessly this virus can spread, unobserved, from animals to humans5 and thus possesses the potential to be a global threat.
Out of 26 patients who tested positive for LayV, the intensity of disease was found to be severe in patients with compromised immunity.9 This emphasizes the need to focus on immunity boosters to prevent disease progression. Centers of disease control and prevention (CDC) suggest symptomatic management of complications with supportive care; however, trials in laboratory studies have shown beneficial results with antiviral ribavirin6. We suggest that extensive research is necessary in the area of vaccines and antiviral treatments.
Had we known about the existence of the SARS-CoV-2 virus in the summer of 2019, before it had successfully jumped to humans, we would have regarded it as an interesting (possibly even concerning) find, but it would have been lumped with many others like it with similar pandemic potential (see 2016's PNAS: SARS-like WIV1-CoV Poised For Human Emergence).
For now, the Langya henipavirus (LayV) ranks pretty far down our threat list, and may never amount to anything more than a local concern and a scientific curiosity.
But nature has a way of surprising us, so it is worth keeping an eye on this new entry into the zoonotic sweepstakes.
