Differences in disease: How COVID-19 compares to SARS and H1N1

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By Philip Smith, assistant professor of kinesiology and health, and Shavon Anderson, university communications and marketing


Philip Smith, assistant professor of kinesiology and health.

As COVID-19 continues to spread across the United States and the world, many communities have lingering questions about the deadly virus and its impact. To help address concerns, Miami’s office of university news and communications connected with Philip Smith, assistant professor of kinesiology and health. Smith has expertise in psychology, epidemiology, health policy, community health and health behavior. In part 4 of a 4-part a series, Smith discusses previous outbreaks in a way that’s easy to understand, in his own words.

Social distancing, quarantine and isolation are all measures being used to slow the spread of COVID-19 and ease the stress on America’s health care system, but there’s still little known on what we’re dealing with. According to updates from the Centers for Disease Control (CDC), COVID-19 is a new, previously unidentified virus. 

For COVID-19, just over the course of about two months, the U.S. saw over 775,000 confirmed cases, although this is likely a major underestimate. Daily deaths rose from less than 100 to over 2,000 in a little over two weeks and have stayed at about that number. The current total is over 40,000 deaths.

To think of a pandemic on a similar scale you would have to think all the way back to the 1918 influenza pandemic. That pandemic caused more loss of life than COVID-19 is likely to cause – around 50 million people worldwide and 675,000 people in the U.S. Of course, the CDC didn’t exist and neither did much of our Department of Health and Human Services. 

So, how does COVID-19 compare to other recent outbreaks? Let’s take a look.

The 2003 SARS outbreak by numbers

In 2003, SARS (severe acute respiratory syndrome) affected 26 countries with a little over 8,000 confirmed cases worldwide. Of those 8,000, 774 people died (about 10%). No one died in the United States.

SARS is caused by a type of coronavirus, different from COVID-19. The version of coronavirus that causes SARS is more deadly but much harder to transmit from person to person. The version of coronavirus that causes COVID-19 is less deadly but much easier to transmit from person to person. 

The differences come down to small biological factors: how long the virus stays in the air, how long it can survive on surfaces, how easily it gets to the lower lungs and how resistant it is to changes in weather or climate. This is why there’s an increased number of people getting sick with COVID-19 compared to SARS. It’s also why health officials worry that COVID-19 could stick around from season to season.

COVID-19 and H1N1

H1N1 is a group of flu viruses that caused the influenza pandemic of 1918, as well as the swine flu pandemic of 2009. Comparing influenza to coronavirus is more like comparing dogs and cats. There are differences between the viruses that make them more or less contagious for people, more or less easily passed from animals to people and more or less severe and deadly. 

Of course, the environment is different as well –– in 2009 and 2020, our health system is much better equipped to handle an epidemic than in 1918. So, let’s compare the 2009 H1N1 outbreak to COVID-19.

H1N1 in the U.S. from 2009-2010:

  • 60.8 million people affected.
  • 274,304 hospitalizations.
  • 12,469 deaths.

Keep in mind, this was spread out over the course of a year. At the time, it affected an incredibly high number of people and caused a tragic loss in life. For a better perspective, consider this: For swine flu in 2009, there were 12,000 deaths in a year. For COVID-19, we’ve already seen 2,500 deaths in a day. The quantity and speed of which people are being hospitalized and are dying of COVID-19 are completely unprecedented in modern history.  


Join Philip Smith for an upcoming May 8 webinar: Miami Presents: Surviving COVID-19 - Making informed decisions during a global pandemic. Smith will teach basic skills for staying informed during the COVID-19 pandemic, empowering the audience to make informed decisions during this unprecedented time of uncertainty. The webinar is intended for a general audience and does not require any prior knowledge of public health or epidemiology.