[Editorial] Langya Virus- the Next Zoonosis

What is Langya Virus?

Langya Virus or LayV is a new zoonotic virus that has evolved to infect humans. It was recently described by the New England Journal of Medicine.
It is a henipavirus and is related to Nipah Virus and Hendra Virus which are known to cause infections and fatal illnesses in humans. Other related viruses include the Mojiang, Cedar and Ghanaian Bat Viruses- which aren’t known to cause human diseases, according to US CDC.
It was identified in China’s Shandong and Henan provinces during routine surveillance.
The virus was identified from the throat swab of a patient and is named after the Shandong province town in which the patient lived. After this, some 35 cases have been identified in this region over a period of 2 years (to 2021).

What are its symptoms?

Some of the symptoms include:
- Fever
- Fatigue
- Cough
- Loss of appetite
- Muscle ache
- Headache
- Nausea
- Thrombocytopenia (low platelet count)
- Leukopenia (low WBC count)
A small proportion of the patients had serious complications like pneumonia, impaired kidney and liver functions.

Where did it come from?

This virus was identified among people who had reported recent contact with animals and suffered from fever. They were mostly farmers.
To identify the virus, the researchers deployed the ‘metagenomic analysis’ technique in which the entire genetic material is sequenced and then the ‘known’ sequences (like human DNA) are discarded while looking for the ‘unknown’ sequence that represent the new virus.
It was identified to be a phylogenetically distinct member of the Henipavirus family- indicating evolution.
While a few goats and dogs were found to be infected with LavY in the past, direct evidence showed that a significant number of wild shrews (a rodent species) carried this virus.

How much of a concern is it?

Traditionally, scientists use the ‘Koch’s Postulates’ to determine whether it was the particular microbe that caused the disease. These are:
The microbe is found in people with the illness, but not among healthy people.
The isolation of the microbe from the diseased people must be possible.
This isolate from the diseased people must cause disease when given to a healthy person/ animal.
The isolation of the microbe from the healthy person (after becoming ill) must be possible.
According to the researchers, the LavY doesn’t meet these 4 criteria. However, the relevance of these criteria in the current times is questioned.
Also, in all patients (except 9 patients), no other pathogen was found except LavY. There is also evidence that some of the patients’ (14 of them) immune system had responded to the LavY. Those who were more sick had a higher number of virus.
While it is unknown whether LavY is capable of human-to-human transmission, when it comes to its close relatives, Henipaviruses are BSL4 (biosafety level 4) pathogens. They cause severe illness among animals and humans.
Hendra Virus, 1^st reported in 1994, have been known to cause outbreaks and deaths among horses. It is considered to be a ‘spillover’ infection from Flying Foxes. Also, 7 human cases and 4 deaths from Hendra Virus infection have been reported from Australia.
Nipah Virus is a more significant relative. The 1^st outbreaks were reported in Singapore and Malaysia. Bangladesh frequently experiences outbreaks. The virus is known to undergo human-to-human transmission.
Currently, there aren’t any licensed drugs or vaccines to protect humans from infection.

What can we do about it?

Though only a little is known about LavY, the currently reported cases are likely to be only the tip of the iceberg. There is no solid evidence for human-to-human transmission and is hence not a particular cause for worry.
However, there is a need for constant surveillance. Regular human and animal screening for emerging viruses is key to understanding and tackling zoonotic diseases.
Taiwan’s Centres for Disease Control is already working on a standardized procedure for genome sequencing and surveillance of the virus.
Information sharing among the nations is also vital given the degree of globalization.
Further work is required to determine how the virus spreads, how severe the infections can get and how widespread it is in China and its vicinity.

Conclusion:

Langya Virus is only the next zoonotic virus in a long list- a list that is expected to grow in the future too. While it isn’t much of a global health concern now, our COVID experience shows the wisdom of preparedness and prevention measures, rather than damage control and mitigation.