WHO’s 2018 annual review of priority diseases list 

The World Health Organization (WHO) has developed a tool for determining which diseases and pathogens to prioritise for research and development in public health emergency contexts. This tool seeks to identify those diseases that pose a public health risk because of their epidemic potential and for which there are no, or insufficient, countermeasures. The diseases identified through this process are the focus of the work of R& D Blueprint. The WHO This is not an exhaustive list, nor does it indicate the most likely causes of the next epidemic. 

The first list of prioritised diseases was released in December 2015 and was reviewed in January 2017. The second annual review took place in February 2018 and experts consider that, given their potential to cause a public health emergency and the absence of efficacious drugs and/or vaccines, there is an urgent need for accelerated research and development for the following diseases:

• Crimean-Congo haemorrhagic 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; and
• Disease X.

‘Disease X’ represents an as yet unknown pathogen that could cause a serious international epidemic. For this reason, the R&D Blueprint explicitly seeks to enable cross-cutting R&D preparedness that is also relevant for an unknown Disease X as far as possible.

A number of additional diseases were discussed and considered for inclusion in the priority list, including: Arenaviral haemorrhagic fevers other than Lassa Fever; Chikungunya; highly pathogenic coronaviral diseases other than MERS and SARS; emergent non-polio enteroviruses (including EV71, D68); and Severe Fever with Thrombocytopenia Syndrome (SFTS).

“These diseases pose major public health risks and further research and development is needed, including surveillance and diagnostics,” says the WHO. “They should be watched carefully and considered again at the next annual review. Efforts in the interim to understand and mitigate them are encouraged.”

Although not included on the list of diseases to be considered at the meeting, monkeypox and leptospirosis were discussed and experts stressed the risks they pose to public health. There was agreement on the need for: rapid evaluation of available potential countermeasures; the establishment of more comprehensive surveillance and diagnostics; and accelerated research and development and public health action.

Several diseases were determined to be outside of the current scope of the Blueprint, including: Dengue; yellow fever; HIV/AIDs; tuberculosis; malaria; influenza causing severe human disease; smallpox; cholera; leishmaniasis; West Nile Virus and plague.

The experts also noted that for many of the diseases discussed, as well as many other diseases with the potential to cause a public health emergency, there is a need for better diagnostics. They also noted that existing drugs and vaccines need further improvement for several of the diseases considered, but that are not included in the priority list.

The impact of environmental issues on diseases with the potential to cause public health emergencies was discussed. This may need to be considered as part of future reviews.

The importance of the diseases discussed was considered for special populations, such as refugees, internally displaced populations, and victims of disasters.

The value of a One Health approach was stressed, including a parallel prioritisation processes for animal health. Such an effort would support research and development to prevent and control animal diseases minimising spillover and enhancing food security. The possible utility of animal vaccines for preventing public health emergencies was also noted.

The WHO noted concerted efforts to address anti-microbial resistance through specific international initiatives and did not exclude the possibility that a resistant pathogen might emerge in the future and would need to be prioritised appropriately.