Risk of ‘catastrophic’ Mers-Covid hybrid behind call for pan-coronavirus vaccine

▶ Case numbers in Africa may be low but our connected world offers diseases a way to spread

Scientists have highlighted an urgent need for a vaccine amid concerns of “catastrophic” consequences if a deadly hybrid is formed between the coronaviruses 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 MersCoV, 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 of 35 per cent for people infected with Mers-CoV.

“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 leading 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.”

In the 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-CoVlike 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 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 “co-infect” cells, perhaps leading to a new hybrid.

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.

Mers-CoV rarely spreads between people, with many cases resulting from people catching it from camels.

The World Health Organisation says the death rate after infection is about 35 per cent, although it said that may be an overestimate, as mild cases may go undetected.

Saudi Arabia is the most heavily affected country, followed by the UAE and South Korea, which suffered an outbreak in 2015. There is no specific vaccine or treatment for Mers.

The high risk of a hybrid virus emerging means vaccines and therapeutics are “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 those working to develop a pan-influenza vaccine, which would be of great value because the dominant strains typically change from year to year. 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.

The focus of this vaccine is helping the immune system to recognise the internal proteins of the virus. 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 related.”

Prof Oxford said a pan-coronavirus vaccine was achievable because knowledge of Sars-CoV-2 could be applied to Mers-CoV.

Mers-CoV is 100 times as deadly as Sars-CoV-2, but because it does not spread easily, it has caused fewer than 900 deaths

When Covid-19 developed into a worldwide pandemic in 2020, perhaps the most frightening aspect of the mysterious new disease was that, at first, there was no vaccine and no treatment. Three years later, the recent re-emergence of the deadly Marburg virus in parts of Africa has rekindled similar fears and highlighted our vulnerability to sickness in an interconnected world.

Marburg, an Ebola-like virus that originated in fruit bats and can spread in humans through direct contact with the bodily fluids of infected people, has a death rate of 88 per cent. Although there are some treatments for specific symptoms that may help a patient survive an infection, there is no known cure.

The latest cases have been reported in Equatorial Guinea and Tanzania – countries that are on opposite ends of the African continent. Although, at 21, the total number of official infections is relatively low, there is no room for complacency, especially in a world where air travel has made it easier than ever for pathogens to move around the globe.

Some might claim that because treatments were eventually developed for Covid, we now live in a post-pandemic world. That feels reassuring, but it is not the case, and pathogenic threats remain. This week, researchers in Shanghai highlighted the “catastrophic” risks posed by a potential hybrid between the viruses that cause Covid and Middle East Respiratory Syndrome, or Mers.

In this scenario, the transmissibility of Sars-Cov-2 could be combined with the death rate of Mers-Cov, which is about 100 times more deadly than Covid.

And it is not just viral illnesses that are concerning. Research from the London School of Hygiene and Tropical Medicine published in this month’s edition of The Lancet Planetary Health found that the use of antibiotics in animals like cattle and chickens is associated with antimicrobial resistance in humans.

However, Marburg is not Covid-19 and over-reactions should be avoided – it is less transmissible than the coronavirus that swept the world in 2020 and the US Centres for Disease Control and Prevention says it is still considered “a very rare disease in people” albeit one that “when it occurs, it has the potential to spread”.

It is a sense of prudence that has informed the decision by the UAE to issue an advisory for citizens and residents to postpone travel to Tanzania and Equatorial Guinea. The Emirates has also advised people travelling to the UAE from the two countries to isolate and visit a health centre for a check-up.

For the countries hit by the outbreak, the economic consequences may prove to be grave. Tanzania is a popular tourist destination and many people there rely on it for their living.

Any assumption that rare diseases are problems for so-called developing countries alone is ill-advised – very few places today can be considered “remote” any more. If Covid-19 taught us anything, it is that illnesses can spread – and change – at a speed that leaves scientists struggling to catch up. The world would do well to remain vigilant.