3 Ways Viruses Can Go Extinct

Viruses, despite their incredible success and abundance, are not invincible. They can, and do, go extinct. Understanding how this happens is crucial, especially when considering the future of viruses like SARS-CoV-2, which causes COVID-19. Here are three primary ways a virus can disappear from the face of the Earth.

1. Running Out of Hosts

For a virus to survive, it needs a continuous supply of hosts to infect. If a virus exhausts its host population, it faces extinction. This nearly occurred with the B/Yamagata flu lineage in early 2020. The widespread implementation of social distancing, mask-wearing, and lockdowns to combat COVID-19 significantly reduced the number of susceptible hosts for B/Yamagata.

• Reduced transmission rates lead to fewer infections.
• Limited host availability can drive a virus to near extinction.
• It remains uncertain if B/Yamagata is truly extinct or merely hiding in an animal reservoir.

Some viruses are so deadly that they kill their hosts, which can paradoxically lead to their own demise. An example of this occurred in 1950s Australia when scientists introduced the myxoma virus to control the European rabbit population. Initially, the virus was highly lethal, killing vast numbers of rabbits. However, the virus evolved to become less deadly, allowing infected rabbits to live longer and spread the virus more effectively. Simultaneously, rabbits evolved to develop better immune responses.

Key Points:

• Highly lethal viruses risk eliminating their host population.
• Viruses can evolve to become less deadly to ensure their survival.
• Hosts can evolve resistance, further impacting viral survival.

2. Human Intervention: Effective Vaccination

Vaccines have proven to be a powerful tool in eradicating viruses. Successful vaccination campaigns have led to the virtual extinction of two viruses: smallpox and rinderpest (which affects cattle). Vaccines work by stimulating the immune system to recognize and fight off viral infections.

The Success of Vaccination:

• Smallpox eradication demonstrates the power of effective vaccines.
• Rinderpest eradication highlights the global impact of veterinary vaccines.
• Vaccines must provide strong protection against infection to be effective.

3. Outcompetition by Other Viruses

Viruses often compete for the same resources and hosts. When a new, more efficient virus emerges, it can outcompete and drive older viruses to extinction. The Delta variant's rapid displacement of the Alpha variant of SARS-CoV-2 is a prime example of this phenomenon.

• Viral competition can lead to the extinction of less efficient strains.
• New variants can emerge with increased transmissibility or virulence.
• Viruses can also coexist by occupying different ecological niches.

Viral Niches:

Viruses don't always compete directly. They can occupy different ecological niches within the same host. For example, influenza infects the respiratory tract, while norovirus infects the intestines. Even within the same cell, viruses can coexist, as seen with hepatitis B and C viruses.

The Future of SARS-CoV-2

Will SARS-CoV-2, the virus responsible for COVID-19, ever go extinct? While new variants will continue to emerge and potentially outcompete existing ones, the virus is now firmly established in the human population. The possibility of eradicating SARS-CoV-2 through vaccination faces challenges, as the virus can persist in animal reservoirs, and current vaccines do not prevent all infections.

Potential Scenarios:

• Continued emergence of new variants.
• Establishment of SARS-CoV-2 in animal populations.
• Development of a universal vaccine that prevents all SARS-CoV-2 infections.

While a cataclysmic event could theoretically wipe out the virus along with humanity, a more realistic hope lies in the development of a universal vaccine. Such a vaccine would need to prevent all SARS-CoV-2 infections, regardless of the variant. Achieving this goal is crucial for long-term control and potential eradication of the virus.

Let's strive towards that second option and work towards a future free from SARS-CoV-2.