Before the COVID pandemic, the World Health Organization (WHO) had made a list Priority infectious diseases. It is felt that they pose an international public health threat, but research is still needed to improve their monitoring and diagnosis. In 2018, “disease x” was included, which meant that a pathogen that was not previously on our radar could cause a pandemic.
Although it is one thing to acknowledge the limits of our knowledge of the microbial soup we live in, more attention has recently focused on how we can systematically deal with future pandemic threats.
Former US Secretary of Defense Donald Rumsfeld famously coined the term “known knowns” (things we know we know), “known unknowns” (things we know we don’t know), and “unknown unknowns” (things we know. Don’t know) talked about (we don’t know).
Although this may be controversial in its original context of weapons of mass destruction, it offers a way of thinking about how we might deal with future pandemic threats.
Influenza: a ‘known known’
Influenza is a largely unknown entity; We essentially have a small pandemic every winter and there are small changes in the virus every year. But more drastic changes may also occur, resulting in its spread into populations with less pre-existing immunity. We saw this most recently with the swine flu pandemic in 2009.
However, we do not understand much about what causes influenza mutations, how these interact with population-level immunity, and how to predict transmission, severity, and impact each year.
The current H5N1 subtype of avian influenza (“bird flu”) has spread widely throughout the world. It caused the deaths of millions of birds and spread to many mammalian species, including cows in the United States and marine mammals in South America.
Human cases have occurred in people who have had close contact with infected animals, but fortunately there is currently no sustained spread between people.
While detecting influenza in animals is a major task in a country as large as Australia, systems are in place to detect and respond to bird flu in wildlife and production animals.
It is inevitable that there will be more influenza epidemics in the future. But this is not always something we should be concerned about.
Avian influenza has focused attention since 1997 when an outbreak in birds in Hong Kong caused severe disease in humans. However the next epidemic in 2009 originated from pigs in central Mexico.
Corona virus: an ‘unknown known’
Although Rumsfeld did not talk about “known unknowns,” the coronavirus would fit into this category. We knew more about coronavirus than most people thought before the COVID pandemic.
We experienced large-scale outbreaks of severe acute respiratory syndrome (SARS) and Middle Eastern respiratory syndrome (MERS). Both are caused by viruses related to SARS-CoV-2, the coronavirus that causes COVID. Although these things may have faded from public consciousness before COVID, coronavirus was listed on the 2015 WHO list of diseases with pandemic potential.
Previous research on earlier coronaviruses proved vital in allowing COVID-19 vaccines to be developed faster. For example, the Oxford group’s early work on the MERS vaccine was crucial to the development of AstraZeneca’s COVID-19 vaccine.
Similarly, previous research on the structure of the spike protein – a protein on the surface of the coronavirus that allows it to attach to our cells – was helpful in developing mRNA vaccines for COVID.
It appears likely that there will be more coronavirus pandemics in the future. And even if they are not on the scale of Covid, the impacts could be significant. For example, when MERS spread to South Korea in 2015, only 186 cases were reported in two months, but the cost of controlling it was estimated at US$8 billion (A$11.6 billion).
25 Viral Families: An Approach to ‘Known Unknowns’
Attention has now shifted towards the known unknown. There are approximately 120 viruses from 25 families that cause human disease. Members of each viral family have similar properties and our immune system reacts to them in similar ways.
An example is the flavivirus family, the best-known members of which are yellow fever virus and dengue fever virus. This family also includes several other important viruses, such as Zika virus (which can cause birth defects if pregnant women are infected) and West Nile virus (which causes encephalitis, or inflammation of the brain).
WHO’s blueprint for pandemics aims to consider the threats posed by different classes of viruses and bacteria. It looks at individual pathogens from each category as examples to systematically expand our understanding.
The US National Institute of Allergy and Infectious Diseases has taken it a step further and has developed vaccines and treatments for a list of prototype pathogens from major virus families. The goal is to be able to adapt this knowledge to new vaccines and treatments if a pandemic arises from a closely related virus.
Pathogen
There are also unknown unknowns, or “Disease X” – an unknown pathogen that has the potential to trigger a serious global pandemic. To prepare for this, we need to adopt new forms of surveillance, especially considering where new pathogens may emerge.
In recent years, there is increasing recognition that we need to take a broader view of health beyond thinking not only about human health, but also animals and the environment. This concept is known as “One Health” and considers issues such as climate change, intensive agricultural practices, the trade in exotic animals, increasing human encroachment into wildlife habitats, changing international travel, and urbanization.
This has implications not only for where to look for new infectious diseases, but also for how we can reduce the risk of “spread” from animals to humans. This may include targeted testing of animals and people who work closely with animals. Currently, testing is primarily directed toward known viruses, but new technologies can look for as-yet unidentified viruses in patients with symptoms consistent with a new infection.
We live in a vast world of potential microbiological threats. While influenza and coronaviruses have a track record of causing past pandemics, a long list of new pathogens can still cause outbreaks with significant consequences.
Continued surveillance for new pathogens, improving our understanding of important virus families, and developing policies to reduce the risk of spread will all be important to reducing the risk of future pandemics.
This article is part of a series on the next pandemic.
Alan Cheng, Professor of Infectious Diseases, Monash University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
