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Do all viruses weaken over time?

Once again, it feels like the end of the pandemic could be on the horizon. What factors are at play to diminish the strength of viruses?

A healthcare worker prepares a Pfizer/BioNtech vaccine against the coronavirus disease during the second booster vaccination program held at a church, in Santiago, Chile, February 7, 2022.
Ivan AlvaradoReuters

Viral evolution is complex. No two are the same, evidenced clearly by the multiple and varied variants of covid-19 that have sprung up in the last two years. That makes it difficult to pinpoint exactly how the covid-19 virus is 'weakening'.

Weaker, in this context, means less likely to cause infection or death. There are two main ways a virus can get weaker, one through a population becoming resistant or totally immune to a virus, or by the virus randomly mutating into a weaker form of itself.

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A population becomes immune

A crucial way to 'weaken' a virus is immunization. Usually, this is done in one of two ways of vaccination or by virtue of having previously contracted the virus. For viruses that are extremely lethal, waiting to get infected is not an option. Vaccination provides human bodies the opportunity to combat a disease before it becomes strong enough to kill them, weakening it.

The most famous example of a disease that was neutralized through inoculation was smallpox. After a serious campaign by the World Health Organization in the second half of the 20th century, the disease was wiped from the planet. This was massively important, as the death rate after contracting the disease was 30 percent, with a higher rate for babies.

Clearly, vaccination had a big impact on 'weakening' the small pox virus. Vaccines have also had a great effect on 'weakening' the covid-19 virus by preventing deaths. Data from the Office for National Statistics in the United Kingdom found, from the period July to December 2021, the risk of death from covid-19 was 93.4 percent lower in the vaccinated compared to unvaccinated people.

For those vaccinated a virus is weaker. For those unvaccinated, it poses serious risk.

A virus becomes less lethal through mutation

Another way a virus can get weaker is through its own mutations. The longer a virus is in circulation, the higher the chance of it mutating. This could change a variety of factors, such as rate of transmission, lethality, how easy it can be tracked by testing, and more. It could stronger or weaker. However, this is completely up to chance. Mutations are random, so there is as much chance of the virus becoming more lethal as it is to become resistant to vaccines.

“We see it go in both directions, becoming more virulent and less virulent. So it certainly shouldn’t be taken for granted that Sars-Cov-2 will simply become milder," says Chris Wymant, Senior Researcher at the Big Data Institute, University of Oxford.

This is similar to what has happened with the covid-19 pandemic. When the Omicron variant surfaced in October there was widespread worry that the variant would be extremely dangerous. This was due to its rapid spread in the first country it was identified, South Africa.

However, as tests were undergone on the variant, it was discovered that Omicron was not as lethal as the preceding Delta variant, despite its rate of transmission. Vaccines had little effect on its transmission as people could be reinfected, sending cases soaring into the hundreds of thousands.

But due to its reduced lethality and the prevalence of vaccines, deaths have not risen to the level that could have been expected if it was April 2020. Of course, this effect is greater in countries with populations that have a very high level of vaccination. The US is still having more than 3,000 covid-19 deaths a day due to having only 64.4 percent of the population double jabbed, one of the lowest rates in North America or Western Europe.

As has been proven throughout the pandemic, the more vaccinated the better. Some countries in Europe have declared the end of the pandemic, while others are lifting restrictions as cases fall. The US is attempting to do the same, but with an intolerable daily death rate from a disease that can be protected against.


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