Story at a glance
- New cases from community spread have made containment impossible for COVID-19.
- The pandemic could naturally trickle off after moving through the population.
- It could become endemic like the flu.
Several states in the U.S. have implemented stay-at-home orders for nonessential workers and mandated closing of nonessential businesses, including New York and California. With the case count climbing past 46,000 in the U.S. and deaths at 600, the federal and state governments are ramping up efforts to fight COVID-19.
Here are some scenarios for how the pandemic could end globally.
The first scenario for how any epidemic could end is containment; if the number of cases are limited to the origin of the outbreak and people who traveled from the origin do not infect more people in other locations, the spread will be minimal.
Before the COVID-19 outbreak officially became a pandemic, there was a possibility for it to be geographically contained.
That possibility was gone with the first reports of community spread in Europe and North America in February. “Once it was established this virus was spreading efficiently between people... we immediately should’ve realized that this was not going to be containable,” says Amesh Adalja at Johns Hopkins Center for Health Security to Vox.
These are other scenarios for how this pandemic could end.
2. Natural trickle off
There’s potential that the number of cases could naturally trickle off, which could be due to a number of things. Other coronaviruses and flu viruses often follow a natural trickle off when the weather gets warmer. The COVID-19 virus, called SARS-CoV-2, may not survive well in more humid conditions, though that has yet to be confirmed.
Cases could also taper off because the virus runs out of susceptible people to infect. "What happens typically is that enough people get the bug that there just aren't enough susceptible people to keep the chain going,” says epidemiologist Joshua Epstein of New York University to Live Science. This is likely to happen more quickly in smaller populations but could take months in larger populations.
There could be a large spike or multiple spikes in cases before it naturally trickles off, and this is under the assumption that nothing that’s being done in response is affecting the outbreak’s trajectory. We’ll get into public health responses later.
3. Pandemic to endemic
Another possibility is that SARS-CoV-2, the virus that causes COVID-19, becomes endemic to humans. This means that it is a normal human disease, like the flu, that enters and reenters the human population for the foreseeable future. “One scenario is that we go through a pandemic,” says epidemiologist Stephen Morse of Columbia University’s Mailman School of Public Health to STAT. “Then, depending what the virus does, it could quite possibly settle down into a respiratory illness that comes back seasonally.”
COVID-19 may be a case where it “could very well become another seasonal pathogen that causes pneumonia,” says infectious disease expert Michael Osterholm of the University of Minnesota to STAT. “The only other pathogen I can compare it to is seasonal influenza.” It could come back year after year, unless we successfully develop a vaccine for it.
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4. Public health response curtails the outbreak
A fourth scenario is one in which we prevent both large spikes in cases and SARS-CoV-2 from becoming endemic by slowing the spread and treating cases of COVID-19 with antivirals and other therapeutic treatments. This is what experts are calling “flattening the curve,” the curve being the trajectory of new cases over time. If we don’t slow the spread, there could be a large spike in cases that could overload the health systems and lead to more deaths, not only in an increase in total deaths but also potentially an increase in proportion to the number of cases.
Without new vaccines or drugs, we can slow the spread by engaging in social distancing, which many governments have already mandated or strongly recommended. Stay-at-home orders can slow the spread if fewer people are contracting the coronavirus from others. If someone does have the virus, they can limit their contact with others so that the spread stops with them.
5. Vaccine development
Creating a vaccine is difficult and takes a long time — at least one year, but potentially much longer. It takes a lot of resources and may not be helpful for dealing with the current pandemic depending on how long it lasts.
Vaccines also do not provide someone with 100 percent immunity; they typically give a range of immunity. For example, two doses of the inactive polio vaccine is 90 percent effective against polio, and three doses is 99 to 100 percent effective. How effective a vaccine is depends on the specific vaccine that is developed, and the most effective vaccine may not be the first vaccine developed. Several companies are currently working on vaccines for SARS-CoV-2.
Another thing to note about vaccines is that it will only help prevent illness before someone gets infected. The main purpose for a vaccine is to prevent future outbreaks. One estimate by epidemiologist Marc Lipsitch of Harvard University says that 40 to 70 percent of people around the world may be infected by SARS-CoV-2 within the coming year, as reported by the Atlantic. If the majority of people in the world are exposed to the virus, then giving them the vaccine may not be very helpful.
However, if we successfully slow the spread, we can use a vaccine to prevent the coronavirus from becoming endemic by protecting the part of the population who hasn’t been exposed to it. If it does become endemic, we may need to treat it like the flu and develop multiple vaccines for it if it mutates over time.
6. Antivirals and other therapeutic treatments
The truth is that we don’t know if any existing drugs will help treat COVID-19. The clinical trial process includes multiple stages to ensure safety and to validate that the drug is effective. Normally, this process could take years, but the Federal Drug Administration may be able to speed it up by fast-tracking approvals. Developing new drugs for COVID-19 would take even longer than getting approval for an existing drug.
The drugs that are being tested in clinical trials are:
Hydroxychloroquine and chloroquine, which are malaria drugs,
Favipiravir or Avigan, a Japanese antiviral drug,
Remdesevir, which was developed for Ebola virus,
Kaletra, an HIV drug, and
Tocilizumab, for treating inflammatory responses.
These drugs may be helpful in treating people, but there is no guarantee they will be effective. If they are helpful, they may lower the severity of illness in people who are infected, consequently decreasing the burden on health systems. Some drugs may prevent someone who is exposed from getting sick by stopping the virus from being able to replicate in the body. Overall, if health systems are not overwhelmed by many people who need to be put into ICUs, there could be a lower death rate.
It’s important to note that having treatments that are effective may not affect the number of cases or the rate of new cases. The best way to prevent new cases is lowering the rate of transmission from person to person, hence social distancing.
An unknown ending
Scenarios are like potential storylines. What happens in reality depends on so many factors that it would be difficult to come up with a scenario that predicts accurately what happens. The point of thinking through scenarios is to visualize potential outcomes and what is or isn’t done to reach those outcomes.
There’s a lot of uncertainty regarding the COVID-19 pandemic. We won’t know if we practiced social distancing effectively enough until long after (and even then the experts will debate about it). We may not know for a while if any existing drugs can help ease the suffering of people with the coronavirus or if they can prevent infection. What we can do now is try to control how many new cases there are and try to not let fear rule our actions and interactions.
For up-to-date information, check the websites of the Centers for Disease Control and Prevention and the World Health Organization. For updated global case counts, check this page maintained by Johns Hopkins University.
You can follow Chia-Yi Hou on Twitter.
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