Researchers from China, Singapore, and Australia reported in a letter published in the New England Journal of Medicine on August 4, 2022, about the identification of the Langya henipavirus (LayV) in a throat swab sample from a 53-year-old woman in Langya, Shandong province, China.
The genome of the LayV was most closely related to the Mojiang henipavirus that was first isolated from rats in an abandoned mine in Yunnan in south China.
Henipaviruses belong to the Paramyxoviridae family of viruses, which includes measles, mumps and many respiratory viruses that infect humans. Several other henipaviruses have been discovered in bats, rats and shrews, from Australia to South Korea and China, but only Hendra, Nipah and now LayV are known to infect people.
The researchers that identified LayV had been monitoring patients with fever at three hospitals in Shandong and Henan between April 2018 and August 2021. They identified 35 patients, mostly farmers, with acute LayV of whom 26 were infected with LayV only with no other pathogens present.
These 26 patients had fever (100 per cent of the patients), fatigue (54 per cent), cough (50 per cent), anorexia (50 per cent), myalgia (46 per cent), nausea (38 per cent), headache (35 per cent), and vomiting (35 per cent), accompanied by abnormalities of low platelets (thrombocytopenia, 35 per cent), low white blood cells (leukopenia, 54 per cent), and impaired liver (35 per cent) and kidney (8 per cent) function.
The symptoms ranged from severe pneumonia to a cough. Most stated in a questionnaire that they had been exposed to an animal within a month of their symptoms appearing.
According to the researchers, the findings from the patients with acute LayV infection suggest that LayV was the cause of febrile illness:
- LayV was the only potential pathogen detected in 26 of the 35 patients (74 per cent) with acute LayV infection.
- In paired serum samples that were obtained from 14 patients during the acute and convalescent phases of infection, the IgG titres in 86 per cent of the convalescent-phase samples were 4 times as high as those in the acute-phase samples.
- Viremia was associated with acute LayV infection.
- Patients with pneumonia had higher viral loads than those without pneumonia.
The researchers did not find strong evidence of LayV spreading between people as there was no obvious spatial or temporal aggregation of human cases and there was no close contact or common exposure history among the patients, which suggests that the infection in the human population may be sporadic.
But retrospective contact tracing was only done on 15 family members of nine patients. This “revealed no close-contact LayV transmission, but the sample size was too small to determine the status of human-to-human transmission for LayV”.
To determine the potential animal origin of LayV, tests were done on goats, pigs, and cattle in the villages of the infected patients. Antibodies against LayV were found in goats (three of 168, 2 per cent) and dogs (four of 79, 5 per cent).
Tissue and urine samples were taken from 25 species of wild small animals to ascertain the presence of LayV RNA. LayV RNA was predominantly detected in shrews (71 of 262, 27 per cent), a finding that suggested that the shrew may be a natural reservoir of LayV, infecting themselves and infecting people by chance.
It was unclear how people were infected in the first place, whether directly from shrews or an intermediate animal.
The researchers conclude that a lot of work was needed to be done to ascertain how LayV is spreading in shrews and how people get infected. They stressed the need for a global surveillance system to detect viral spread from animals to humans and rapid communication to avoid more pandemics like Covid-19.
Hendra And Nipah Viruses
The Hendra virus (HeV) was first isolated in 1994, during an outbreak of respiratory and neurologic disease in horses and humans in the Brisbane suburb of Hendra, Australia.
The outbreak involved 21 stabled racehorses and two human beings who died. To date, seven human beings have contracted HeV following exposure to body fluids, tissues, or excretions of infected horses, with four dead, a mortality rate of 57 per cent. HeV has not been reported outside northeast Australia.
A commercial HeV vaccine for horses has recently been licensed in Australia.
Malaysia was the first country in the world to encounter the Nipah (NiV) outbreak in 1998 and 1999. It resulted in the near decimation of the pig rearing industry which was then the largest in ASEAN, with about a million pigs culled. Many of the human beings who survived have been left with residual complications.
The initial NiV cases were reported near Ipoh in September 1998. Four of 28 of these cases tested positive for IgM antibodies against Japanese Encephalitis (JE) and a JE outbreak was declared by the Health Ministry.
The pigs were sold and transferred out of Perak. By the end of 1998, more cases were reported in Bukit Pelandok in Port Dickson district.
In March 1999, Chua Kaw Bing isolated NiV from a patient resident in Sungai Nipah village who was treated at University Hospital, University of Malaya. The outbreak eventually caused 283 cases and 109 deaths (J Clinical Virology 2003: 26: 265-275) with a mortality rate of 38.5 per cent.
A NiV outbreak (11 cases, one death) was also reported in Singapore among slaughterhouse workers in March 1999. Since then, there have been outbreaks in Bangladesh in 2001, with annual outbreaks, and eastern India. The fatality rate of NIV ranges from about 40 to 75% depending on the clinical management capabilities.
Most human NiV infections in Malaysia resulted from unprotected exposure to secretions of sick pigs or their contaminated tissues. Subsequent outbreaks in Bangladesh and India, however, were most likely due to consumption of fruits or fruit products from infected fruit bats. These bats, which are the natural reservoir of NiV, have been found in Indonesia, Philippines, Thailand, Cambodia, Ghana and Madagascar.
Human-to-human NiV transmission have been reported among family and care givers of the infected through close contact with their secretions and excretions. NiV in Bangladesh and India have been reported in health care settings due to transmission through providing care.
NiV outbreaks have been reported in domestic animals like pigs, horses, goats, sheep, cats and dogs. An infected pig can be asymptomatic but some develop fever, difficulty breathing and neurological symptoms like trembling, twitching and muscle spasms. The mortality rate in pigs is usually low except for young piglets.
There is no treatment or vaccine available for NiV in humans or animals.
The Langya (LayV) is a henipavirus, of which only the Hendra, Nipah (“NiV”) and now LayV viruses are known to infect humans.
Although there has been no NiV outbreak in Malaysia since about two decades ago, only the very brave can vouch that it would not recur. Could LayV occur in Malaysia? Only time will tell.
There is an urgent need for the Health and Agriculture Ministries to provide updated public information about its surveillance of both the NiV and LayV viruses in humans and animals.
Dr Milton Lum is a Past President of the Federation of Private Medical Associations, Malaysia and the Malaysian Medical Association. This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation the writer is associated with.
- This is the personal opinion of the writer or publication and does not necessarily represent the views of CodeBlue.