.jpg)
Disease X is aplaceholder name that was adopted by theWorld Health Organization (WHO) in February 2018 on their shortlist ofblueprint priority diseases to represent a hypothetical, unknownpathogen.[4][5] The WHO adopted the placeholder name to ensure that their planning was sufficiently flexible to adapt to an unknown pathogen (e.g., broader vaccines and manufacturing facilities).[4][6] Former Director of the USNational Institute of Allergy and Infectious DiseasesAnthony Fauci stated that the concept of Disease X would encourage WHO projects to focus their research efforts on entire classes of viruses (e.g.,flaviviruses), instead of just individual strains (e.g.,zika virus), thus improving WHO capability to respond to unforeseen strains.[7]
In 2020, experts, including some of the WHO's own expert advisors, speculated thatCOVID-19, caused by theSARS-CoV-2 virus strain, met the requirements to be the first Disease X.[1][2][3] In December 2024, anunidentified disease in theDemocratic Republic of the Congo was sometimes referred to as Disease X, after infecting over 400 people and killing at least 79, later revealed to be an aggressive strain of malaria.[8]
In May 2015,in pandemic preparations prior to the COVID-19 pandemic, the WHO was asked by member organizations to create an "R&D Blueprint for Action to Prevent Epidemics" to generate ideas that would reduce the time lag between the identification of viral outbreaks and the approval of vaccines/treatments, to stop the outbreaks from turning into a "public health emergency".[4][10] The focus was to be on the most seriousemerging infectious diseases (EIDs) for which few preventive options were available.[10][11] A group of global experts, the "R&D Blueprint Scientific Advisory Group",[12] was assembled by the WHO to draft a shortlist of less than ten "blueprint priority diseases".[4][5][10]
Since 2015, the shortlist of EIDs has been reviewed annually and originally included widely known diseases such asEbola andZika which have historically caused epidemics, as well as lesser known diseases which have potential for serious outbreaks, such asSARS,Lassa fever,Marburg virus,Rift Valley fever, andNipah virus.[5][11] Since then,COVID-19 has been added to the list.[13]
In February 2018, after the "2018 R&D Blueprint" meeting inGeneva, the WHO added Disease X to the shortlist as a placeholder for a "knowable unknown" pathogen.[4][6][14] The Disease X placeholder acknowledged the potential for a future epidemic that could be caused by an unknown pathogen, and by its inclusion, challenged the WHO to ensure their planning and capabilities were flexible enough to adapt to such an event.[5][15][16]
At the 2018 announcement of the updated shortlist of blueprint priority diseases, the WHO said: "Disease X represents the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease".[5][6][17]John-Arne Røttingen, of the R&D Blueprint Special Advisory Group,[9] said: "History tells us that it is likely the next big outbreak will be something we have not seen before", and "It may seem strange to be adding an 'X' but the point is to make sure we prepare and plan flexibly in terms of vaccines and diagnostic tests. We want to see 'plug and play' platforms developed which will work for any or a wide number of diseases; systems that will allow us to create countermeasures at speed".[6][11] US expertAnthony Fauci said: "WHO recognizes it must 'nimbly move' and this involves creating platform technologies", and that to develop such platforms, WHO would have to research entire classes of viruses, highlightingflaviviruses. He added: "If you develop an understanding of the commonalities of those, you can respond more rapidly".[7]
Jonathan D. Quick, the author ofEnd of Epidemics, described the WHO's act of naming Disease X as "wise in terms of communicating risk", saying "panic and complacency are the hallmarks of the world's response to infectious diseases, with complacency currently in the ascendance".[18]Women's Health wrote that the establishment of the term "might seem like an uncool move designed to incite panic" but that the whole purpose of including it on the list was to "get it on people's radars".[19]
Richard Hatchett of theCoalition for Epidemic Preparedness Innovations (CEPI), wrote "It might sound like science fiction, but Disease X is something we must prepare for", noting that despite the success in controlling the 2014Western African Ebola virus epidemic, strains of the disease had returned in 2018.[20] In February 2019, CEPI announced funding of US$34 million to the German-basedCureVacbiopharmaceutical company to develop an "RNA Printer prototype", that CEPI said could "prepare for rapid response to unknown pathogens (i.e., Disease X)".[21]
Parallels were drawn with the efforts by theUnited States Agency for International Development (USAID) and theirPREDICT program, which was designed to act as an early warning pandemic system, by sourcing and researching animal viruses in particular "hot spots" of animal-human interaction.[22]
In September 2019,The Daily Telegraph reported on howPublic Health England (PHE) had launched its own investigation for a potential Disease X in the United Kingdom from the diverse range of diseases reported in their health system; they noted that 12 novel diseases and/or viruses had been recorded by PHE in the last decade.[23]
In October 2019 in New York, the WHO'sHealth Emergencies Program ran a "Disease X dummy run" tosimulate a global pandemic by Disease X, for its 150 participants from various world health agencies and public health systems to better prepare and share ideas and observations for combatting such an eventuality.[24][25]
In March 2020,The Lancet Infectious Diseases published a paper titled "Disease X: accelerating the development of medical countermeasures for the next pandemic", which expanded the term to includePathogen X (thepathogen that leads to Disease X), and identified areas of product development and international coordination that would help in combatting any future Disease X.[26]
In April 2020,The Daily Telegraph describedremdesivir, a drug being trialed to combat COVID-19, as an anti-viral thatGilead Sciences started working on a decade previously to treat a future Disease X.[27]
In August 2023, the UK Government announced the creation of a new research center, located on thePorton Down campus, which is tasked at researching pathogens with the potential to emerge as Disease X. Live viruses will be kept in specialist containment facilities in order to develop tests and potential vaccines within 100 days in case a new threat is identified.[28]
In January 2024, during theWorld Economic Forum's annual meeting, Disease X was once again discussed as being a potential threat following the COVID-19 pandemic.[29][30]
A paper published in 2022 listed the following strategies in preparation for Disease X:[31]
On the addition of Disease X in 2018, the WHO said it could come from many sources citinghemorrhagic fevers and the more recentnon-polio enterovirus.[6] However, Røttingen speculated that Disease X would be more likely to come fromzoonotic transmission (an animal virus that jumps to humans), saying: "It's a natural process and it is vital that we are aware and prepare. It is probably the greatest risk".[6][11] WHO special advisor Professor Marion Koopmans, also noted that the rate at which zoonotic diseases were appearing was accelerating, saying: "The intensity of animal and human contact is becoming much greater as the world develops. This makes it more likely new diseases will emerge but also modern travel and trade make it much more likely they will spread".[11][32]
From the outset of theCOVID-19 pandemic, experts have speculated whetherCOVID-19 met the criteria to be Disease X.[33][34] In early February 2020, Chinese virologistShi Zhengli from theWuhan Institute of Virology wrote that the first Disease X is from a coronavirus.[3] Later that month,Marion Koopmans, Head of Viroscience atErasmus University Medical Center inRotterdam, and a member of the WHO's R&D Blueprint Special Advisory Group,[9][35] wrote in the scientific journalCell, "Whether it will be contained or not, this outbreak is rapidly becoming the first true pandemic challenge that fits the disease X category".[2][36][37] At the same time,Peter Daszak, also a member of the WHO's R&D Blueprint, wrote in an opinion piece inThe New York Times saying: "In a nutshell, Covid-19 is Disease X".[1]
At the 2018 announcement of the updated shortlist of blueprint priority diseases, the media speculated that a future Disease X could be created intentionally as abiological weapon.[38] In 2018, WHO R&D Blueprint Special Advisor Group member Røttingen was questioned about the potential of Disease X to come from the ability ofgene-editing technology to producesynthetic viruses (e.g., the 2017 synthesis ofOrthopoxvirus in Canada was cited), which could be released through an accident or even an act ofterror. Røttingen said it was unlikely that a future Disease X would originate from a synthetic virus or a bio-weapon. However, he noted the seriousness of such an event, saying, "Synthetic biology allows for the creation of deadly new viruses. It is also the case that where you have a new disease there is no resistance in the population and that means it can spread fast".[11]
In September 2019, Public Health England (PHE) reported that the increasingantibiotic resistance of bacteria, even to "last-resort" antibiotics such ascarbapenems andcolistin, could also turn into a potential Disease X, citing theantibiotic resistance in gonorrhea as an example.[39]
In 2018, theMuseum of London ran an exhibition titled "Disease X: London's next epidemic?", hosted for the centenary of theSpanish flu epidemic from 1918.[40][41]
The term features in the title of several works of fiction that involve global pandemic diseases, such asDisease (2020),[42] andDisease X: The Outbreak (2019).[43]
Disease X has become the subject of severalconspiracy theories, claiming that it may be a real disease, or conceived as a biological weapon, or engineered to create a planned epidemic.[44][45]
By listing Disease X, an undetermined disease, the WHO is acknowledging that outbreaks do not always come from an identified source and that, as it admits, "a serious international epidemic could be caused by a pathogen currently unknown to cause human disease".
This hope now looks forlorn with the sudden emergence of the respiratory disease Covid-19, which has rapidly acquired most of the characteristic of a Disease X.
