Scientists have highlighted an "urgent" need for a vaccine to combat all coronaviruses amid concerns over "catastrophic" consequences if a deadly hybrid is formed between the viruses that cause Covid-19 and Middle East Respiratory Syndrome.
The danger is that a hybrid could combine the transmissibility of Sars-CoV-2, the pathogen that leads to Covid-19, and the high death rate of Mers-CoV, the cause of Mers.
In a new study, three researchers at the Shanghai Institute of Infectious Disease and Biosecurity highlighted the "astonishingly high" death rate for people infected with Mers-CoV of about 35 per cent.
"Even as Sars-CoV-2 continues its worldwide spread, Mers-CoV remains a threat," the scientists wrote in Signal Transduction and Targeted Therapy, which is linked to Nature, one of the world’s top scientific journals.
"Mers-CoV is the most virulent human pathogenic coronavirus known to date, even though only sporadic infections have been reported in the Middle East since 2016."
New virus could pose deadly threat
In their paper, published last month, the researchers said that an "even more concerning" recombinant virus — one that combines the genetic material of more than one virus — could be named Sars-CoV-3 or Mers-CoV-2.
"It is likely that such a new [group of viruses] may bear high Sars-CoV-2-like transmissibility along with a high Mers-CoV-like case-fatality rate, which would have catastrophic repercussions," the scientists wrote.
Mers-CoV is about 100 times as deadly as Sars-CoV-2, they said, but because it does not spread easily, it has caused fewer than 900 deaths since emerging in 2012.
When it infects human cells, Sars-CoV-2 uses a receptor on those cells called Ace2 while Mers-CoV and similar coronaviruses enter through a different receptor, DPP4.
Certain human cells in the lungs and intestines have both types of receptors, leading to the risk that the two viruses could "coinfect" cells, potentially leading to recombination between them.
Prof John Oxford, emeritus professor of virology at Queen Mary, University of London and an author of the textbook Human Virology, said coronaviruses were "known for gene swapping".
"They can swap whole chunks of genes and recombine with other members of the family," he said. "It’s a very good topic to be interested in and an important one."
Mers-CoV only rarely spreads between people, with a large proportion of cases resulting from people catching the virus from camels.
The World Health Organisation states that the death rate after infection is about 35 per cent, although it cautions that this may be an overestimate, as mild cases may go undetected.
Saudi Arabia has been the most heavily affected country, followed by the UAE and South Korea, the latter of which suffered an outbreak in 2015. There is no specific vaccine or treatment for MERS.
"Given the high risk of Sars-CoV-2/Mers-CoV recombination, the development of pan-β-CoV vaccines [which would protect against a wide variety of coronaviruses] as well as CoV entry and replication inhibitor-based therapeutics is urgently needed to combat the pandemics or epidemics caused by emerging Sars-CoV-3 or Mers-CoV-2 in the future," the researchers wrote.
Prof Oxford is among the researchers who has been working to develop a pan-influenza vaccine, something that would be of great value because the dominant strains of influenza causing illness typically change from year to year.
As was widely reported, in November scientists forecast that a universal flu vaccine, based on the messenger RNA (mRNA) technology behind successful Covid-19 vaccines, could be available within two years following successful experimental work.
The focus of this vaccine is helping the immune system to recognise the internal proteins of the influenza virus, as Prof Oxford said these were less variable than external proteins.
"It would be a good idea to apply that to the coronavirus," he said. "You will look for internal proteins which are the same. Many of them are very much related when they’re in the same family."
Prof Oxford said producing a pan-coronavirus vaccine was "probably achievable now" because more is known about the internal structure of Sars-CoV-2, and this knowledge could be applied to Mers-CoV.