Explainer: What's Disease X? Why there can be another pandemic on the way

This hypothetical, unknown pathogen lurking out there, which has the potential to trigger a future epidemic, has been nicknamed as 'Disease X'.

Disease X has come under the spotlight of late as a UK health expert in a media interview shared her fears about new viruses out there setting off another pandemic deadlier than COVID-19.

Kate Bingham, who served as the chair of the UK's Vaccine Taskforce from May to December 2020, created quite a stir when she said that a new virus can very easily turn out to be lethal for humans. And, potentially, can be as deadly as the devastating Spanish Flu of 1919-1920, which had killed more than 50 million people worldwide.

So, what is Disease X, why is it deadly and causing so much concern?

What is Disease X?

Disease X, as its name suggests is an unknown pathogen. It can be a virus, a bacterium or fungus without any known treatments.

The World Health Organisation (WHO) first explained it thus: Disease X represents the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease.

While the Coalition for Epidemic Preparedness Innovations warned that it may "sound like science fiction", but Disease X is something we must prepare for.

What causes Disease X?

It is supposed to be caused by a “pathogen X.” Such a pathogen is expected to be a zoonosis, most likely an RNA virus, emerging from an area where the right mix of risk factors will help it to transmit at a sustained level.

When was the term first coined and by whom?

In 2018, the WHO had coined the term Disease X, a year before the COVID-19 pandemic struck. The global health body has been putting out a list of priority diseases that pose the greatest public health risk as they can cause an epidemic or they lack insufficient countermeasures. On the list are diseases like COVID-19, Ebola, Lassa fever, Middle East respiratory syndrome (MERS), Nipah and Zika.

Disease X too finds a mention on this list. These diseases are of high priority in terms of research and development. What the scientific community fear is that these unexpected Disease X outbreaks may completely take the medical world by surprise.

In May this year, at a World Health Assembly meeting in Geneva, Dr Tedros Adhanom Ghebreyesus, the WHO director-general issued a warning regarding this outbreak. Tedros warned that ‘another epidemic can come at any time, which can spread a terrible disease and also kill a large number of people’.

What will be the impact of a Disease X?

What sounds ominous is that Bingham, who is the author of the book, The Next Killer: How to Stop the Next Pandemic Before It Starts, written along with Tim Hames, a former journalist and political advisor, said that Disease X is expected to be considerably more dangerous than COVID-19.

It can cause 20 times more fatalities than the coronavirus, which claimed more than 2.5 million people around the world. She asks people to imagine Disease X as infectious as measles with the fatality rate of Ebola. And, she adds that somewhere in the world, it's replicating, and sooner or later, "somebody will start feeling sick”.

Ebola had a fatality rate of around 67 per cent, while bird flu and MERS also killed a large number of people. Bingham felt that the next pandemic cannot be so easily contained as the COVID-19 pandemic and seems to think we had it easy with the coronavirus.

According to Bingham, the 1918-19 flu pandemic killed at least 50 million people worldwide. She felt that today, we could expect a similar death toll from one of the many viruses that already exist.

How many (Disease X) viruses are out there?

Scientists say that there are plenty of viruses and they are diverse. There are more viruses busily replicating and mutating than all the other life forms on our planet combined. However, not all of them pose a threat to humans but plenty do, said scientists.

Bingham said that scientists have identified 25 virus families which contain thousands of individual viruses, and millions are yet to be discovered, and these have the potential to evolve into pandemics.

How can Disease X threats be countered?

The world will have to prepare for mass vaccination drives and deliver the doses in record time, said Bingham. Scientists felt R&D and working out counter-measures are essential to quickly contain an epidemic.

WHO scientists are already working on R&D, vaccines, tests and treatments of the priority pathogens on their list that can cause outbreaks or pandemics.

"This list of priority pathogens has become a reference point for the research community on where to focus energies to manage the next threat,” said Dr Soumya Swaminathan, former WHO Chief Scientist on the world health agency website. “It is developed together with experts in the field, and is the agreed direction for where we—as a global research community—need to invest energy and funds to develop tests, treatments and vaccines," she added. 

Scientists are saying that there’s an urgent need to invest in vaccine research and development, strengthen health systems and surveillance, and enhance global cooperation and coordination to be able to counter the threats posed by these unknown viruses of Disease X.

What's the status on vaccine development for these unknown viruses?

Currently, no approved vaccines are available. Scientists need to develop a collection of "different prototype vaccines for every threatening virus family", said Bingham, who seems to want a 'head start' on vaccines to target specific features of Disease X.

Also, vaccines are required to counter different facets of the virus as well. For different types of vaccines stimulate different immune responses and therefore they provide different levels of protection.

Why pandemics are increasing

The rise in outbreaks, according to Bingham, is attributed to the growing trend of more people cramming into urban areas. People are increasingly connected due to globalisation.

The continual destruction of millions of acres of natural habitat each year is also playing a role.

Three-quarters of emerging infectious diseases originate in animals and then leap from species to species until they can, in certain circumstances, infect human beings. Deforestation, modern agricultural methods and the destruction of wetlands are facilitating a breeding ground for Disease X viruses.