Health

Understanding zoonotic diseases: Is COVID-19 Disease X that WHO warned of in 2018?

Disease X predictions: mortality rate higher than seasonal flu; spread as easily as the flu; shake financial markets even before turning pandemic

 
By Vibha Varshney
Published: Wednesday 06 May 2020
World's largest physics meeting cancelled due to COVID-19 fears. Source: Pixabay

In 2018, the World Health Organization (WHO) released a list of 10 diseases that can cause epidemics; all were viral in nature. Besides the usual suspects such as Zika, Ebola and Severe Acute Respiratory Syndrome (SARS) — triggered by a coronavirus, it also had a Disease X, to be caused by an unknown pathogen. There is now a growing consensus that COVID-19 is Disease X. 

“This outbreak (COVID-19) is rapidly becoming the first true pandemic challenge that fits the Disease X category,” writes Marion Koopmans, head, viroscience department, Erasmus University Medical Centre in The Netherlands in the journal, Cell.

Peter Daszak, who was part of the WHO team that collated the 2018 list, writes in the New York Times that they had postulated that Disease X would be viral, originate in animals and would emerge in a place where economic development drives people and wildlife together. The group predicted that the disease would be confused with other diseases during the initial stages and would spread quickly due to travel and trade.

Disease X would have a mortality rate higher than seasonal flu and would spread as easily as the flu. It would shake the financial markets even before it became pandemic. “In a nutshell, COVID-19 is Disease X,” he writes. This flies in the face of WHO’s expectations that the next pandemic would be that of influenza.

The devastation caused by COVID-19 pandemic is a rude reminder of the fact that the world needs to better understand and manage epidemics. “Our understanding of infectious diseases has improved. But we don’t fully understand all aspects regarding the emergence of epidemics,” says Suresh V Kuchipudi, clinical professor and associate director, Animal Diagnostic Lab, Department of Veterinary and Biomedical Sciences, the Pennsylvania State University.

He, however, highlights a similarity among the past few epidemics: “RNA (ribonucliec acid) viruses have caused all the recent major outbreaks, including COVID-19.” Due to their inherent nature to mutate and evolve, RNA viruses are more likely to cause future epidemics.

WHO tracked 1,483 epidemic events in 172 countries between 2011 and 2018. Nearly 60 per cent of the recent epidemics were zoonotic, of which 72 per cent originated in wildlife. Besides COVID-19, WHO reported nine disease outbreaks in the first 79 days of 2020.

Climate change and environmental degradation are making matters worse as they help viruses to mutate faster, thus increasing the rate of spread. RNA viruses have mutation rates that are up to a million times higher than their hosts.

These high rates are correlated with enhanced virulence and evolvability, traits considered beneficial for viruses, wrote Siobain Duffy, associate professor at the School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, in PLoS Biology in 2018.

Viral diseases are difficult to control and the limited knowledge about them adds to the challenge. Despite decades of experience, scientists are not even close to finding an effective method to contain a viral outbreak.

In fact, the currently used contaiment methods such as social isolation and closing down of schools were also used during the deadly Spanish flu in 1917-1918. The methods did not work then, and they do not seem to be working now. Even the much-promoted hand washing might not be as effective as is being expected.

Researchers at the University of Hong Kong found that personal protective measures such as hand hygiene or face masks and environmental hygiene measures such as improved hygiene and environmental cleaning do not help reduce transmission of influenza.

Despite the mounting threat, there are no global comprehensive surveillance efforts that proactively monitor the emergence of potential pandemic viruses. In 2018, a project (Global Virome Project) was launched to develop a global atlas of most of the planet’s naturally occurring potentially zoonotic viruses over the next 10 years.

Scientists today know just over 260 viruses in humans, which cumulatively account for just 0.1 per cent of potential zoonoses. In other words, the world remains ignorant about 99.9 per cent of potential zoonotic viruses.

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