Disease X has been formerly included on the WHO’s Blueprint priority list since March 2017. And spokesman Tarik Jasarevic has re-emphasised the importance of preparing for the unknown. He said: “The Research and Development (R&D) Blueprint is a global strategy and preparedness plan that allows the rapid activation of R&D activities during epidemics.
“Its aim is to fast-track the availability and use of effective tests, vaccines and medicines that can be used to save lives and avert large scale crisis.
“The R&D Blueprint focuses on a priority list of diseases with outbreak potential, and for which there are no or insufficient medical countermeasures (drugs and vaccines), and no major control initiatives or extensive research pipelines.”
Mr Jasarevic stressed the list was not exhaustive, nor did it indicate the most likely causes of the next epidemic.
But he added: “Disease X is the unknown, something that we have not seen before.
“It is a placeholder to a disease that can emerge and cause harm.
“It represents the knowledge that a serious epidemic could be caused by a currently unknown pathogen, or a known pathogen with changed characteristics leading to increased severity, and/or expanded geographic range.
“No one can say when and where this will happen, but recent examples have made us aware that other viruses with poorly-known pathologies may be waiting in the wings.”
At the moment, Disease X is theoretical in the sense that no specific disease has been identified – but Mr Jasarevic said the description could have been applied to many disease which have since become recognised as posing a serious public health threat, such as swine flu and Zika.
He said: “Nearly all recent epidemics have been caused by viruses that jump from animals to humans, known as zoonotic diseases.
“Ecosystem and human habitats changes, modern travel and trade make it much more likely for zoonotic disease to spread.
“However, if these viruses are our enemy, we do not yet know our enemy very well.
“So, disease X could be sparked by a zoonotic virus that then spreads to become an epidemic or a pandemic.
“This has happened many times during the last decade: H1N1 Swine flu virus in 2009, Severe Acute Respiratory Syndrome (SARS) in 2002, Middle East respiratory syndrome (MERS) in 2012, and more recently Zika in South America in 2015.”
Mr Jasarevic stressed the importance of being prepared for the illnesses the nature of which is not yet known.
He said: “We should be aware that the unknown can happen, and make sure we prepare and plan flexibly in advance of any epidemics.
“For example, platforms for developing vaccines, drugs, and diagnostic tests that will work for any or a wide number of diseases, including an unknown disease, and will allow us to create countermeasures quickly.
“However, while products to detect, prevent, treat and control these diseases are fundamental, they are not sufficient unless there are basic capabilities in the affected countries that will improve disease surveillance and the capacity of local health systems, which would help in turn to detect and respond to an outbreak quickly.”