#17,233
Although many people think that the SARS-CoV-2 virus came without warning, in truth, while the exact SARS-CoV-2 virus that sparked the COVID pandemic had not been reported prior to December 2019, several closely related cousins were already on our radar.
- Twenty years ago, the first severe human coronavirus - SARS-CoV - burst onto the world's stage (see SARS and Remembrance) after being hidden by Chinese officials for months, causing at least 8,000 infections and 800 deaths.
- In 2012 another coronavirus (MERS-CoV) virus was discovered affecting humans in the Middle East. It was eventually linked to camels, and has caused at least 2,600 infections and 935 deaths (likely a huge undercount) - and while reported cases are down - it remains a pandemic concern.
- We've seen numerous discoveries of novel coronaviruses - mostly in bats - around the world, many believed to have pandemic potential (see 2016's PNAS: SARS-like WIV1-CoV Poised For Human Emergence).
- And since the emergence of SARS-CoV-2 several related coronaviruses have been found in bats both in, and outside of, China (see Nature: Coronaviruses Closely Related to the Pandemic Virus Discovered in Japan & Cambodia).
While it was more of a lucky guess than a flash of genius, six weeks before the Wuhan outbreak, in a blog called African Swine Fever's (ASF) Other Impacts; Pharmaceuticals, Bushmeat, and Food Insecurity, I speculated that China's ASF outbreak could lead to increased `bushmeat' consumption, which in turn might spark another SARS-like outbreak.
The point being, we'd seen so many emerging coronaviruses over the previous 15 years or so, the notion that a novel coronavirus could spark the next pandemic wasn't that far-fetched.
Novel influenza viruses, which are known to have sparked dozens of pandemics over the past 500 years, are still on the top of our list, but there are plenty of other more exotic contenders, including Ebola and Marburg viruses, Lassa Fever, Rift Valley Fever, Nipah and/or Hendra, and Monkeypox.
Anytime we see a spillover of a zoonotic virus into humans, we should be paying attention, even if it isn't particularly common, or deadly.
Viruses evolve over time and have the ability to adapt to new hosts - and while most will fail in that endeavor - it only takes one overachiever to spark the next global health crisis.
A little over 5 months ago we learned of a previously unknown novel zoonotic henipavirus in China's eastern Shandong and Henan provinces in NEJM: A Novel Henipavirus With Human Spillover In China, which had infected at least 35 humans and had been isolated in a number of farm animals.
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.
Henipaviruses - of which Nipah and Hendra are the most infamous - 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.
Six weeks later, in J. Virus Erad: A Review Of The Langya Virus Outbreak in China, 2022, we looked at a more detailed review of this emerging virus, where the authors wrote:
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 good news is - as far as we know - this virus is not transmitting from human-to-human. But how good, or reliable, surveillance from China - which is already dealing with a massive wave of COVID - is, is unknown.
H-2-H transmission is something we have seen with other henipaviruses (Nipah), meaning we can't entirely discount the possibility.
While the Langya virus currently sits pretty far down our list of pandemic concerns, it is worth keeping an eye on. This past week an editorial was printed in the journal Virulence, which discusses its (still largely unquantified) pandemic potential.
Follow the link to read the article in its entirety, as I've only posted some excerpts. After the break I'll have a brief postscript.
Langya henipavirus: Is it a potential cause for public health concern?
Shania Sanchez & Hinh Ly (2023) Langya henipavirus: Is it a potential cause for public health concern?, Virulence, 14:1, 2154188, DOI: 10.1080/21505594.2022.2154188
A new virus, named Langya henipavirus (LayV), has recently been identified in Shandong and Henan provinces in China and has so far infected 35 individuals between April 2018 and August 2021. It is closely related to other known henipaviruses (Nipah and Hendra viruses) that can cause up to 70% human case fatality.Even though LayV has not been shown to be fatal in humans and does not appear to be transmitted from human-to-human, it is an RNA virus with the capacity to evolve genetically in the infected hosts (e.g. shrews) and can infect humans (e.g. farmers who have been in close contacts with shrews). It is therefore important to be vigilant about this new viral outbreak.
(SNIP)
While bats, rodents, and shrews are thought to act as reservoirs for Nipah and Hendra viruses, a recent survey of more than two dozen wild species of animals suggests that shrews are the natural hosts of LayV [2], yet it isn’t clear whether they are primary or intermediate hosts of the virus [1,2], before it can be transmitted to people via direct contact with the infected animals. In fact, patients who have been tested positive for LayV are farmers who reported to have been in contact with shrews within a month of their symptom onsets. Symptoms of the disease include fever, fatigue, cough, loss of appetite, muscle pain, nausea, headache and vomiting [2].Some patients have been diagnosed with more severe disease, such as liver and/or renal failure syndromes and/or decreased white blood cell count and low platelets [2]. Even though it has been reported that patients infected Figure 2. Transmission of LayV from shrew to human is known, but it is unclear whether human-to-human transmission of LayV is also possible.with LayV can shed viruses via blood, urine, faeces and saliva [5], so far, there is no evidence to suggest that LayV can be transmitted from human to human (but rather through zoonotic spillover events) (Figure 2).
Spillover of novel viruses, such as LayV and SARS-CoV-2, which is the causative viral agent of the current COVD-19 pandemic, has been strongly associated with close human interactions with animals (for a review, see [6]). Therefore, it is essential to understand how these events occurs to prevent future viral disease outbreaks and to minimize their societal impact [7].
While LayV is so far not an immediate cause for public health concern, it is an RNA virus with a relatively high degree of mutability (i.e., relatively high error rate of genomic RNA replication mediated by the error-prone RNA-dependent RNA polymerase [8]) and has the ability and potential to evolve genetically and to undergo rapid antigenic variations in the infected hosts, and therefore could become highly problematic if it is left unchecked.
Therefore, it is essential that surveillance methods, such as those used during the 2018 outbreak of Nipah virus [9] that include serosurveys and longitudinal spatial and temporal studies to detect virus shedding and to isolate the virus from the likely animal reservoirs can help mitigate the potential threat that LayV may pose to humans.
(Continue . . . )
Granted, it is hard to give too much thought to the creek rising when your house is already on fire, but we can't assume that we'll be out of the woods once we `get past' our current COVID emergency. The world is a big place, and has an excellent track record as being an effective incubator for new viruses.
While I can think of a dozen other viruses with greater pandemic potential than Langya, our ability to accurately predict the next pandemic virus remains frustratingly elusive.
The best we can do right now is to assume the next one is already out there, evolving and adapting, and could emerge at any time. It could be milder than COVID, or it could worse.
But either way, we need to be prepared to deal with it when it comes.
