For some, the COVID-19 pandemic may be over. For others, it feels like it will never end. We learn from history that the plague will indeed end eventually. But when exactly will this end, and what will it take to finally get back to "normal"?
The world health organization WHO officially declared COVID-19 as an epidemic in March 2020. A disease becomes an epidemic if it spreads across countries, continents and / or regions and if it spreads easily from person to person, infecting a large number of people.
"Pandemics are whenever a disease spreads rapidly around the world," said Casey Pinto, assistant professor of public health sciences at Penn State College of Medicine.
So a pandemic starts with a disease, usually a new one like COVID-19, then spreads rapidly around the world. But, when and how will it end?
"That's a great question that experts around the world are thinking about right now because it's very difficult to say when the epidemic will end," Pinto said.
The WHO says there has never been a pandemic caused by the Corona virus. They define several phases of the influenza pandemic, one of which is the post-pandemic period.
"At this stage, the level of influenza activity has returned to the level seen in seasonal influenza in most countries with adequate surveillance," according to the WHO.
COVID-19 is caused by a Corona virus that is different from the influenza virus. But the post-pandemic definition can provide some clues as to when the epidemic will finally end.
"Although the specifics are not clear, the main problem when the pandemic ends is when we can say that the virus stops spreading easily among the population," said Pinto.
How the epidemic ended
There are several factors that contribute to reaching the point when the virus stops spreading easily. But one of the biggest factors is achieving herd immunity, and not just achieving herd immunity in one country, but the whole world.
"Because we are a very connected society, people will be traveling between countries and between countries, so herd immunity needs to be achieved across the country and the world for the epidemic to end," Pinto said.
Although the exact threshold for herd immunity is unknown, experts estimate that we need at least 70% of people to be immune to the virus.
Researchers can estimate the percentage of people who need to be immune to the virus to achieve herd immunity by comparing COVID-19 to other diseases with similar transmission rates.
"Like measles, we know that we need about 93% of the population to be vaccinated or have natural immunity through exposure to prevent measles outbreaks. With COVID, because it is almost as contagious as measles, we may need about 90% of people to be immune," said Pinto.
Learning from the 1918 flu epidemic
Since the outbreak of COVID-19, people have compared it to the flu pandemic of 1918. A total of 25 million people died in the first six months since the virus spread. The epidemic took about 18-20 months to completely end. But the virus didn't go away, and the same thing experts predict will happen to COVID-19.
"Just like the flu, experts think COVID-19 will become endemic, which means it will occur frequently in our population. And, like the flu, we may need to be revaccinated periodically to prevent serious illness," he said.
Regardless of the future of COVID-19, Pinto and health experts and scientists remind the public that the epidemic is not over. Keeping a social distance, washing hands diligently, wearing a mask, and immediately getting vaccinated is our defense now.
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