Pandemics: What are they and when will we see another?

Joseph Giambrone, professor emeritus in the Auburn University College of Agriculture’s Department of Poultry Science with a joint appointment in the College of Veterinary Medicine’s Department of Pathobiology, has penned this article about various impending worldwide pandemics.

A pandemic is an epidemic of an infectious disease that has spread across a large region affecting a substantial number of individuals. Pandemics are complex and unpredictable events that can be caused by new infectious diseases or the emergence of existing ones in a novel and virulent form. The occurrence of a pandemic depends on numerous factors, including the interactions between humans, animals and the environment, as well as the ability of a pathogen to spread rapidly and cause severe illness. While scientists and health organizations continuously monitor and study infectious diseases to prevent and mitigate their impact, it is impossible to predict with certainty when the next pandemic will happen.

“Remember it is not if but when we will see the next pandemic.”

Many serious human pathogens result from zoonotic transmission, including 61% of known human pathogens and 75% of emerging human pathogens. For example, the rabies virus is transmitted by saliva of infected animals. The plague bacteria (Yersina pestis), the causative agent of the largest documented pandemic in human history that reduced the population of Europe by 30-50%, was transmitted from rats to humans by fleas. Other zoonoses include Ebola virus, tularemia (Francisella tularensis) and tuberculosis. The recent coronavirus pandemics, thought to have a bat reservoir, with intermediate spillover into animals has stimulated renewed emphasis on zoonotic pathogen surveillance. 

That being said what we can do is to remain vigilant, invest in public health infrastructure, support scientific research and follow guidelines and recommendations from health authorities to prevent and control the spread of infectious diseases. By learning from past experiences, we can better prepare for future pandemics.

The emergence of a new pandemic can be caused by numerous factors. Some of the probable causes include:

Zoonotic spillover: Many pandemics have originated from animal viruses that jumped to humans through a process called zoonotic spillover. This happens when a virus from an animal species infects a human, and if it has the ability to transmit efficiently between humans, it can lead to widespread outbreaks.

Mutation of existing pathogens: Pathogens, such as viruses and bacteria, can undergo mutations that enhance their ability to infect humans or become more virulent. These mutations can lead to the emergence of new strains with pandemic potential.

Global travel and connectivity: Modern transportation systems enable rapid and widespread movement of people across the globe. This can facilitate the spread of infectious agents to various parts of the world, increasing the risk of a pandemic.

Urbanization and population density: Increasing urbanization and population density create conditions that favor the rapid transmission of infectious diseases among large groups of people.

Antibiotic resistance: The rise of antibiotic-resistant bacteria is a significant concern. If an untreatable or difficult-to-treat bacterial infection were to spread widely, it could lead to a health care crisis.

Environmental changes: Human activities that lead to environmental changes, such as deforestation, habitat destruction and climate change, can disrupt ecosystems and bring humans into closer contact with new pathogens.

Agricultural practices: Intensive and industrial agricultural practices can create environments that favor the emergence and spread of infectious diseases, both in animals and humans.

Bioweapons research: Though not a common cause, there are concerns that research on biological weapons could inadvertently or intentionally lead to the creation of a new pathogen with pandemic potential.

Monitoring and surveillance of infectious diseases, with rapid response, are essential to detect and contain outbreaks before they escalate into a pandemic.

There were several pathogens known to have pandemic potential. It is important to note that the list may change over time as new pathogens emerge or are better understood. Some of the pathogens that have been identified as having the potential to cause a pandemic include:

Avian Influenza (bird flu) viruses, particularly those with high mutation rates that are endemic in wild migrating waterfowl, are known to cause flu pandemics in humans.

Coronaviruses: Coronaviruses have caused recent pandemics, such as the one caused by SARS-CoV-2, which led to COVID-19. Other coronaviruses, like those responsible for SARS (severe acute respiratory syndrome) and MERS (Middle East Respiratory Syndrome), also have pandemic potential. MERS-CoV and SARS-CoV: These viruses could cause future pandemics if they mutate to become more easily transmissible between humans.

Ebola virus: Ebola virus outbreaks have been sporadically reported in Africa, and while they have not led to global pandemics, the potential for a more transmissible strain exists.

Zika virus: The Zika virus, primarily transmitted by mosquitoes, has been linked to birth defects and neurological problems. Although it caused outbreaks in specific regions, its global spread raised concerns about its pandemic potential.

Drug-resistant bacteria: Pathogens with antibiotic resistance, such as methicillin-resistant Staphylococcus aureus (MRSA) and extensively drug-resistant tuberculosis (XDR-TB), could potentially cause widespread and difficult-to-treat infections.

Nipah virus: The Nipah virus, which can cause severe respiratory and neurological symptoms, has caused outbreaks in Southeast Asia, and has the potential to cause a pandemic if it gains the ability for sustained human-to-human transmission.

Hantaviruses: Certain hantaviruses, like the Sin Nombre virus, can cause hantavirus pulmonary syndrome (HPS) and have potential pandemic risk if they acquire efficient human-to-human transmission.

Remember that the potential for a pathogen to cause a pandemic depends on several factors, including its ability to spread efficiently between humans, evade immunity and cause severe disease. Health authorities, researchers and organizations continuously monitor these pathogens to detect and respond to potential outbreaks and prevent them from becoming pandemics.