What pathogen could cause the next pandemic? How scientists are preparing for “disease X”

Before the Covid-19 pandemic, the World Health Organization (WHO) did made a list priority infectious diseases. They were considered to pose a threat to international public health, but were still needed research to improve their surveillance and diagnosis. In 2018 “X disease”, which meant that a pathogen we had not previously observed could cause a pandemic.

While it’s one thing to acknowledge the limits of our knowledge of the microbial soup we live in, recent attention has turned to how we might systematically approach future pandemic threats.

Former US Secretary of Defense Donald Rumsfeld famously talked about “known knowns” (things we know that we know), “known unknowns” (things we know that we don’t know), and “unknown unknowns” (things that we don’t know that we don’t know) .

While this may have been controversial in the original context of weapons of mass destruction, he asserts a way to think how we can approach future pandemic threats.

Flu: ‘the known known’

Influenza is a largely known disease; Basically, we have a minor pandemic every winter with minor variations in the virus each year. However, more severe changes may also occur, resulting in spread in populations with little pre-existing immunity. The last time we saw this was in the 2009 case swine flu pandemic.

But there is much we don’t understand about the factors that drive flu virus mutations, how they interact with population-level immunity, and how to best predict transmission risk, severity and impact each year.

The current subtype of avian influenza H5N1 (“bird flu”) spread widely around the world. This led to death many millions birds and spread to several species of mammals including cows in the United States and marine mammals in South America.

Human cases have been reported in people who have had close contact with infected animals, but fortunately there is currently no sustained spread between humans.

Although detecting influenza in animals is a huge task in a vast country like Australia, it does exist on-site systems detecting and responding to bird flu in wild and production animals.

It is inevitable that there will be more flu pandemics in the future. But it’s not always the one we worry about.

Attention has been focused on avian influenza since 1997, when the country experienced an avian flu epidemic Hong Kong caused severe disease in humans. But next pandemic in 2009 comes from pigs in central Mexico.

Coronaviruses: ‘the unknown known’

Although Rumsfeld did not talk about “unknown unknowns”, coronaviruses would fit into this category. We knew more about coronaviruses than most people thought before the Covid-19 pandemic.

We have had experience with Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) causing vast epidemics. Both are caused by viruses closely related to SARS-CoV-2, the coronavirus that causes COVID disease. Although they may have disappeared from public awareness before the pandemic, coronaviruses were included in the 2015 list of infections WHO list diseases with pandemic potential.

Previous research on earlier coronaviruses has proven crucial in enabling the rapid development of vaccines against Covid-19. For example, the Oxford group’s initial work on MERS vaccine was key to the development of AstraZeneca’s Covid-19 vaccine.

Similarly, previous research on structure spike protein – a protein found on the surface of coronaviruses that allows them to attach to our cells – was helpful in the development of mRNA vaccines for Covid.

It seems likely that there will be further coronavirus pandemics in the future. And even if they do not occur on the scale of a pandemic, the effects could be significant. For example, when MERS spread in South Korea in 2015, it caused only 186 cases in two months, but the cost of controlling it was is estimated at $8 billion (A$11.6 billion).

25 virus families: an approach to ‘known unknowns’

Attention now turned to the known unknowns. There are approximately 120 viruses 25 families known to cause disease in humans. Members of each virus family share common properties, and our immune systems respond to them in similar ways.

An example is flavivirus familythe most notable members of which are the yellow fever virus and the dengue virus. This family includes too several other critical viruses, such as the Zika virus (which can cause congenital defects in case of infection of pregnant women) and West Nile virus (which causes encephalitisor encephalitis).

WHO epidemic plan aims to consider the threats posed by different classes of viruses and bacteria. It examines individual pathogens as examples from each category to systematically expand our knowledge.

The U.S. National Institute of Allergy and Infectious Diseases went a step further by making vaccines and therapies appear on the list prototypical pathogens from key virus families. The goal is to be able to adapt this knowledge to modern vaccines and treatments in the event of a pandemic caused by a closely related virus.

Pathogen X, “unknown unknowns”

There are also unknown unknowns, i.e. “X disease” – an unknown pathogen that may cause a stern global epidemic. To prepare for this, we must adopt modern forms of surveillance, focusing especially on places where modern pathogens may emerge.

In recent years, there has been an increasing recognition of the need for a broader view of health, going beyond thinking about the health of humans, but also of animals and the environment. This concept is known as “One health” and takes into account issues such as climate change, intensive agricultural practices, the exotic animal trade, increased human encroachment on wildlife habitats, changes in international travel and urbanization.

This has consequences not only where to look for modern infectious diseases, but also how we can reduce the risk of disease “spillover” from animals to humans. This may include targeted research animals and people who work closely with animals. Currently, testing mainly focuses on known viruses, but new technologies can look for yet unknown viruses in patients with symptoms consistent with modern infections.

We live in a huge world of potential microbiological threats. While influenza and coronaviruses have a history of causing pandemics in the past, a longer list of modern pathogens can still cause epidemics with significant consequences.

Continued surveillance of modern pathogens, improving our understanding of critical virus families, and developing policies to reduce the risk of virus transmission will be critical to reduce the risk of future pandemics.

This article is part of a series on the next pandemic.