Disease X and future pandemics in the age of climate crisis

What is Disease X?

Disease X is the concept promoting preparedness for future pandemic events by stipulating potential pathogens capable of causing outbreaks on a large scale. The causative agent, which could be any microbe, is designated ‘Pathogen X’.

Why is it important?

The concept of Disease X allows the global community to know what to look for in microbes capable of causing major pandemics, and, most important of all, to prepare the necessary resources to control emerging infectious diseases.

In fact, COVID-19 did fit this concept. Members of the Coronavirus family have always been considered potential threats since the inception of the Disease X concept because they were the causal agents of SARS and MERS. When the news of the emerging SARS-like Coronavirus, later designated SARS-CoV-2, became known at the end of 2019, the public health networks in several countries immediately started to monitor the outbreak situation and set up control measures.

What could be Pathogen X?

In principle, Pathogen X might come from any kind of microbes including viruses, bacteria, fungi and parasites. They could also be new strains of known disease-causing pathogens. Therefore, it is important to regularly monitor circulating microbes from the environment, wildlife and vector samples, making genomic surveillance a necessity.

How to monitor the unknown?

The key is regularly monitoring microbes in circulation to capture changes in microbial dynamics that may develop over time. The collection programmes should explore samples from the environment, wastewater, animal reservoir and vector insects. The state of technology now allows us to decode genetic materials without the need to fully cultivate microbes. Millions of sequencing reads can be deciphered to match existing genomes to determine the species, and even be used to identify unknown pathogens. Most importantly, the collection of sequencing data can eventually lead to the development of detection, prevention and treatment tools.

Risk amplification by climate and environmental crises

A major detrimental factor exacerbating the risk for emerging diseases is the ongoing climate and environmental crises. For example, bats forced out of their natural habitats need to move closer to humans and domestic animals for resources. This event led to the spillover of zoonotic viruses. Similar scenarios have become more common in recent years, which makes active investigations of microbial pools a priority.

Major caveats

Having the data showing the genomic repertoires of circulating microbes is vital for risk estimation. However, this alone does not lead to risk reduction. The development of methods and tools for prevention, diagnosis and treatment must be explored simultaneously to take full advantage of the genomic data. This means that the genomic data must be shared between countries; however, poorer nations are disadvantaged for a variety of reasons. This disparity will dissuade developing countries, often located in geographical areas prone to disease outbreaks, from open data sharing. Hence, global mechanisms to reward data transparency and data sharing must be considered.

Another major concern is the safety issue associated with laboratory handling. Samples collected for genomic surveillance might contain novel microbes that can harm laboratory workers and communities nearby. Safety measures based on local laws and regulations must always be taken into account.

Further Reading

Disease X: accelerating the development of medical countermeasures for the next pandemic

Pathogen spillover driven by rapid changes in bat ecology

Diversity and evolution of the animal virome

Do you think resources should be allocated to detect pathogen X and prepare for future pandemics? If not, what should be the priority instead? Please share your views in the comments.