Seasonal or Occasional Outbreaks

To better understand SARS-CoV-2, researchers looked at previous pandemics such as the 1918 Spanish flu and the Black Death in the 14th century. What are the possible outcomes of the current pandemic?

In 1918, the influenza pandemic affected nearly one-third of the world's population at the time in four waves. Two years later, the virus became drastically less deadly. Today, it has evolved into the seasonal flu.

A few centuries earlier, the Black Death killed nearly 200 million people in Europe within four years. Until today, the contagion is still very deadly and there has been no developed vaccine for the bubonic plague yet. However, today's available treatment can help patients recover if they are hospitalized on time.

Transmissibility and Virulence

In the past few months, scientists have published several studies on how the coronavirus has evolved since the original strain in Wuhan was sequenced. Although the virus has already hit several countries in two or three waves, scientists still hope that similar to former pandemics, coronavirus will also gradually become less deadly over time.

Evolutionary biologist Paul Ewald proposed several years ago that when a germ is deadlier, the less likely it is to spread since it relies on the host which kills white quickly. He calls this the "theory of virulence," where the deadliness of a virus or bacteria would eventually decline.

The theory also proposes that germs have specific strategies to become infectious that results in high transmissibility and virulence, such as SARS-CoV-2. Factors such as durability in various environments could prevent a virus from becoming less deadly. Another factor of coronavirus is that it is more stable than influenza.

According to Ewald, coronavirus is nearly as durable as influenza since pathogens can remain on surfaces for hours or days. He believes that the future evolution of coronavirus will be similar to seasonal influenza that arrives during late fall until early spring.

However, predicting the pandemic's outcomes is complex since global records are likely to be inaccurate. This is the result of various testing methods, false negative or positive results, cases that are unaccounted for, and other factors.

Moreover, a lot of research has focused on the increasing transmissibility of coronavirus and not its lower virulence. For example, by June, a team from the Scripps Research Institute published a study that the original D614 Wuhan strain evolved into the G614 in the Americas and in Europe which was ten times more deadly.

A month later, another team from Los Alamos National Laboratory, confirmed that the coronavirus evolved into a more infectious strain. However, researcher Bette Korber said that "infectiousness and transmissibility are not always synonymous." Virologist Nathan Grubaugh, who was not involved in either study, said that there is also a huge difference between transmission observed in laboratories and live infections between people.

Virologist Vincent Racaniello said that coronavirus "may become less deadly, not because the virus changes, but because very few people will have no immunity. For example, if a child is exposed to the virus, recovers, then get infected again as an adult, they would most likely get a mild infection. Experts around the world believe that when the current pandemic will end, coronavirus may become seasonal. Occasionally, an outbreak may even occur in areas where people remain unvaccinated.

Check out more news and information on the Coronavirus on Science Times.