Disease X: an unknown disease that could claim millions of lives

Dubbed ‘Disease X’, scientists believe a future epidemic of the influenza virus could cause millions of deaths worldwide, mimicking the effects of the Spanish Flu of 1918.

Illustration of potential disease x - which is likely to share similarities with influenzacigdem | Shutterstock

With globalized trade, increased connectivity between countries, and higher numbers of people traveling frequently, large outbreaks of infectious diseases are “becoming inevitable”, a Research and Development (R&D) Blueprint brochure states.

The R&D Blueprint is a “global strategy and preparedness plan” that aims to make tests, vaccines, and medicines quickly available during epidemics to avoid a large-scale crisis.

The Blueprint began after the Ebola epidemic taught the World Health Organization (WHO) that “we […] must advance the new development of new medical products to detect, prevent and treat infectious disease with epidemic potential.”

In May 2015, 194 Member States requested that the World Health Organization bring together a network of experts to devise the R&D Blueprint to prevent and control epidemic outbreaks.

The 2018 Annual Review of the Blueprint identifies the diseases and pathogens that should be prioritized for research.

First assembled in 2015 and reviewed in 2017, the list highlights the diseases that have insufficient countermeasures, some of which have no countermeasures in place at all. Such diseases are thought to pose a significant risk to public health.

Recently reviewed again for 2018, the list flags up the following diseases as requiring urgent research and development. It is important to note that the diseases are not ranked by urgency, nor is it an exhaustive list of diseases highlighted for research and development.

  • Crimean-Congo hemorrhagic fever (CCHF)
  • Ebola virus disease and Marburg virus disease
  • Lassa fever
  • Middle East respiratory syndrome coronavirus (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS)
  • Nipah and henipaviral diseases
  • Rift Valley fever (RVF)
  • Zika
  • Disease X.

Disease X represents the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease.”

World Health Organisation

Currently, there is no disease called Disease X. However, the precedent for the effects of Disease X is set with the Spanish Flu in 1918, an influenza pandemic that claimed 5% of the world’s population.

It is thought that if Disease X mirrors the pandemics of the past, it could leave healthy individuals with the strongest immune systems most at risk.

Spanish Flu is believed to have caused “cytokine storms” in patients due to the body’s immune system attacking itself.  Such events occur when the body’s immune system produces an overwhelming amount of contradictory signals that eventually prove fatal.

The study “Pandemic Versus Epidemic Influenza Mortality: a pattern of changing age distribution” claims that the highest numbers of fatalities were unusually seen in people under the age of 65, with conclusions being drawn that the stronger the immune system, the more vulnerable it actually was to Spanish Flu.

A different theory is that older generations had, by the time of the 1918 Spanish Flu pandemic, built up more resistance to influenza infections through exposure to other strains, and as such, they were better protected than their younger peers.

Comparing three outbreaks of influenza A in 1918, 1957, and 1968, the “Pandemic Versus Epidemic” study shows that large proportions of fatalities were among younger populations, but deaths among younger people “accounted for decrementally smaller proportions of deaths during the first decade following each pandemic”.

It goes on to suggest that the “large proportion of influenza-related deaths during each pandemic and the following decade among persons <65 years old should be considered in planning for pandemics.”

Influenza viruses mutate extremely quickly and some strains can be passed between animals and humans, meaning predicting or pinpointing outbreaks can be difficult.

In 2015, the WHO recorded 212 cases of avian influenza A(H7N9) that resulted in death out of 571 lab-confirmed cases. While avian flu A(H7N9) does not transmit well to humans, Dr. Jonathan Quick said that outbreaks can be made more dangerous through person-to-person contact:

Our greatest fear is being blindsided by a new virus, most likely due to animal-human spillover, which then readily spreads from human to human, has at least a 5 to 10 per cent fatality rate, does not respond to existing medicines, and for which an effective vaccine and accurate diagnostic test cannot rapidly be developed.”

Jonathon Quick, Chair of the Global Health Council

Hoping that we can deal with an outbreak of an unknown disease more effectively in the future and saving countless lives, WHO science adviser Rottingen says that “history tells us that it is likely the next big outbreak will be something we have not seen before, and that the “the point is to make sure we prepare and plan flexibly in terms of vaccines and diagnostic tests.”

Lois Zoppi

Written by

Lois Zoppi

Lois is a freelance copywriter based in the UK. She graduated from the University of Sussex with a BA in Media Practice, having specialized in screenwriting. She maintains a focus on anxiety disorders and depression and aims to explore other areas of mental health including dissociative disorders such as maladaptive daydreaming.


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