Explained | Disease X: Tracking the next pandemic

What steps is the WHO taking to stay ahead of future public health crises?

Updated - December 07, 2022 04:18 pm IST

Published - November 29, 2022 01:04 pm IST

Representational image

Representational image | Photo Credit: Keith Bishop

The story so far: World Health Organisation (WHO) on Monday said that it is updating the list of priority pathogens that “pose the greatest public health risk due to their epidemic potential and/or whether there is no or insufficient countermeasures”.

The process, which started on Friday, involves more than 300 scientists from across the world , considering evidence on around 25 virus families and bacteria, as well as “Disease X”. The process is expected to guide global investment and research and development(R&D) in vaccines, tests, and treatments.

Currently, Covid-19 is at the top of the priority disease list.

What is Disease X?

Disease X refers to an unknown pathogen that can cause the next pandemic. It is part of WHO’s priority diseases list prepared for R&D in a public health emergency context. According to WHO, it represents “the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease”.

How is WHO tracking the next pandemic?

WHO relies on R&D Blueprint – a global strategy and preparedness plan – to avert large-scale health crises. The R&D Blueprint includes goals and research priority areas to accelerate the development of testing, vaccines, and therapeutics of diseases caused by the listed priority pathogens. The WHO uses this blueprint to guide responses to outbreaks and improve global response for future epidemics – covered under and as “Disease X”.

The need to develop such a blueprint was sharply felt during the 2014 Ebola outbreak in West Africa. The medical community was ill-prepared to deal with the disease’s rapid spread, and the lack of treatment drugs, vaccines, and trained healthcare professionals compounded the problem. While the outbreak was eventually controlled through quarantine and travel restrictions, community awareness, and coordinated international efforts, it nudged the WHO towards preparing for similar public health concerns in the future. In May 2015, the organisation convened a network of experts to develop the R&D Blueprint for Action to Prevent Epidemics.

According to WHO, the following gaps in R&D were found during the Ebola pandemic:

  • Platforms that expedite vaccine clinical trials, drug testing and data sharing,
  • a broader R&D scope that encompassed, for example, a better understanding of the disease, animal models, and personal protective equipment,
  • community engagement plans from the outset, and
  • funding sources that could be quickly activated.

The Blueprint also works with partners, including the Coalition for Epidemic Preparedness Innovations (CEPI) and the Global Research Collaboration for Infectious Disease Preparedness (GloPID-R).

What is an R&D roadmap?

An R&D roadmap gathers the knowledge collected through stakeholder effortand identifies the main activities needed to “promote strategic research in advance of and during outbreaks.”.

Like most roadmaps, it is a concise and comprehensive document, outlining a collaborative framework that includes basic research to late-stage development, licensure and early use of products. These R&D roadmaps serve as important tools to identify effective health technologies and save lives by integrating “research into response”.

More about the R&D Blueprint

For each disease on the list of priority pathogens, an R&D roadmap is created, followed by target product profiles (TPP). This framework is then used to guide outbreak responses — both urgent action and global response to potential future pandemics.

The blueprint uses three different approaches to establish preparedness in dealing with disease outbreaks— improving coordination and fostering an enabling environment, accelerating R&D processes, and developing new norms and standards for epidemics.

When an outbreak is recorded, the blueprint moves from R&D preparedness to an emergency R&D response plan. This includes WHO coordination and planning to facilitate the implementation of research response, and mobilisation of external stakeholders.

The 2016 Zika outbreak emerged as a testing ground for the R&D Blueprint. Initial activities included developing the landscape of existing research, product development for the disease, and consultation with world experts to identify knowledge gaps and agree on a plan for accelerating product development.

In April 2016, WHO came up with TPPs for Zika virus diagnostic tests, while a TPP for vaccines against the disease and the associated congenital syndrome was released in July of that year. The Emergency Use Assessment and Listing (EUAL) procedure, established during the Ebola outbreak, was opened for Zika in vitro diagnostics in the following February.

The current list of priority diseases

WHO’s current list of priority diseases includes:

  • Covid-19
  • Crimean-Congo haemorrhagic fever
  • 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
  • Zika virus disease
  • Disease X

When is the updated list expected?

WHO conducted its last prioritisation exercise in 2018. A new updated list is expected to be released in the first quarter of 2023. Efforts towards building the updated list will draw on lessons from the Covid-19 pandemic, WHO announced.

The new prioritisation exercise

The prioritisation exercise will adopt a viral family approach – identifying “representative viruses (or prototypes) within a viral family as a pathfinder in generating science, evidence and filling knowledge gaps that may then be applied to other viruses of threat in the same family”. This approach allows for fast-track research on entire families of viruses instead of individual strains, thus broadening the knowledge of experts and improving response to unforeseen strains, including those that may cause Disease X.

Experts will review the science related to around 25 viral family groups and shortlist viruses of concern. One bacterial group will also be added to ensure that risks of naturally occurring bacterial threats are accounted for. In the first phase of the exercise, experts will shortlist priority viral families, prototype viruses and bacteria, and Disease X recommendations.

During the second phase, scientific and public health criteria (public health impact, health equity, economic and societal impact) will be considered for a deeper review of the shortlist. An independent Prioritisation Advisory Committee (PAC) will conduct the final prioritisation following a multi-criteria decision analysis (MCDA) approach.

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