Why have we recently witnessed an increase in the emergence of viruses?

From COVID-19 to avian flu and monkeypox, it seems that the number of emerging viruses has increased in recent years. But what is the reason?

From the widespread outbreak of monkeypox  in 2022 to the ongoing spread of avian flu and recent cases of Marburg virus in Equatorial Guinea, COVID is no longer the headline it used to be. Instead, we constantly hear about the spread of emerging viruses or the resurgence of past viruses.

So, have viral outbreaks increased or have we simply gotten better at detecting them thanks to advanced technologies in the wake of the COVID pandemic? The answer may be a combination of both.

Lindsey Broadbent, a virologist at the University of Surrey in the UK, writes on The Conversation that an estimated 1.67 million viruses are currently infecting mammals and birds that have not yet been identified. It is believed that of this number, around 827,000 have the potential to infect humans.

To understand how viruses appear, we need to go back to the beginning of life on earth. There are several theories about how viruses first emerged, but all experts agree that viruses have been evolving alongside living organisms for billions of years. When a disturbance in this evolution occurs, we run into trouble.

The main drivers of virus emergence in human populations are humans and their actions. Agriculture has been widespread for over ten thousand years, and during this time, close contact between humans and animals began. This gave viruses that naturally infected animals the opportunity to jump species and infect humans. These types of diseases are called zoonoses, or diseases shared by humans and animals. About 75% of emerging infectious diseases are due to this type of infection.

The progress of human civilization, technology, and the destruction of natural habitats have forced animals to seek food in new areas. Different species that were usually not in contact with each other are now in a common environment. Add humans to this equation, and you have a complete recipe for the emergence of new viruses.

Urbanization leads to high population density and provides an ideal environment for the spread of viruses. The rapid development of cities often outpaces infrastructure such as health systems and sanitary care, which increases the likelihood of viral transmission.

Climate change has also contributed to the spread of viruses. For example, arboviruses (viruses transmitted by insects such as mosquitoes) are being identified in new regions. This is because the range of countries where mosquitoes can survive is increasing.

We have known about these factors for a long time. The emergence of SARS-CoV-2 (the virus that causes COVID-19) did not surprise any virologist or epidemiologist. Experts had predicted the occurrence of new global pandemics. What was unexpected was the scale of the COVID-19 outbreak and the difficulty in containing the efficient spread of the virus.

We have also been unable to anticipate the impact of false information on public health. Anti-vaccination beliefs have become more prevalent on social media in recent years, and we are witnessing an increase in doubt about vaccines. Disruptions in childhood vaccination programs have also created a risk of preventable infectious diseases, such as measles.

Lessons learned about virus surveillance

Science has moved at an unprecedented pace during the pandemic, leading to the development of new methods and improvement of previous methods for virus detection for surveillance of the spread and evolution of viruses.

Now, many scientists who worked on tracking SARS-CoV-2 have shifted their focus to monitoring other viruses. For example, during the pandemic wastewater surveillance was used for SARS-CoV-2 detection, and this method can also help track other viruses that are a threat to human health.

When a person becomes infected with a virus, usually some of the virus’s genetic material is expelled from their body and finds its way to the sewage system. Sewage has the power to typically indicate that the number of infections in an area is on the rise before the start of an increase in the number of cases in hospitals.

Modifying the aforementioned technology to find other viruses like influenza, measles, or even polio can provide valuable information about the timing of virus outbreaks. This is currently being done to some extent. For example, in 2022, polio was identified in London’s sewage.

An increase in monitoring viruses will naturally lead to reports of more outbreaks. While some people may find this terrifying, such information can be the key to controlling future pandemics. If an outbreak occurs in an area with insufficient virus surveillance, the likelihood of the infection spreading to an uncontrollable extent is higher.

Of course, monitoring is only one part of preparedness for a pandemic. Governments and health and scientific organizations worldwide must have up-to-date pandemic and virus emergence protocols to take control of the situation in a timely manner.

It is unlikely that COVID will be the last pandemic in the lifetimes of most humans currently living on Earth. But we hope to be more prepared to deal with the next pandemic.