COVID-19 and the Flu Don’t Compare

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The novel coronavirus, SARS-CoV-2, that causes COVID-19, has been compared at times to the flu. The flu kills tens of thousands of Americans every year. Yet we don’t shut down businesses, close schools and issue “Stay Home, Stay Healthy” orders to limit the spread of the flu. What makes the coronavirus so different? Why do we need to take strong action such as physical distancing with COVID-19? While the full picture is not yet complete, it’s increasingly clear that the flu, while it should be taken seriously, pales in comparison to COVID-19

  1. Novel coronavirus spreads more rapidly than the flu.

While all flu strains are slightly different, research shows that, on average, a person infected with the flu infects 1.28 additional people. By contrast, a person infected with the novel coronavirus spreads the virus to two or three additional people.

What does this look like? Even if we take the conservative estimate of spreading COVID-19 to just two people instead of three, you can see that the spread of the virus happens much more rapidly than the spread of the flu.

COVID-19 Spreads Rapidly

2. COVID-19 is contagious longer before people start showing symptoms, meaning people are more likely to spread it before they know they’re sick.

With the flu, you typically have symptoms between one to four days after exposure, with most people showing symptoms after two days, and are contagious 24 hours before you feel sick Once people start feeling sick with the flu, they generally stay home, minimizing the spread of the virus.

Infected people start showing symptoms of COVID-19 one to 14 days after exposure, with most people showing symptoms after four or five days. It appears that the coronavirus can spread 48 to 72 hours before the onset of symptoms, and we’re discovering some people have minimal or no symptoms at all. These people don’t know that they have COVID-19 and may not follow social distancing guidelines. In turn, they can pass the virus along to people who may get severely ill or even die from COVID-19. This is one possible explanation for why people who are infected with the virus spread it to more people than the flu.

3. COVID-19 doesn’t seem to slow down with warmer weather, like the flu.

In the U.S., flu season usually begins in the fall and lasts until March or sometime in early spring, with the peak in cases occurring between December and February. As the weather warms, flu activity generally decreases. While there are many reasons why this may be the case, research shows that the virus spreads more easily in cooler temperatures. Higher temperatures can cause degradation of the flu virus in a much shorter time.

With COVID-19, however, there’s no guarantee that warmer weather will slow the spread. Countries such as Singapore, Indonesia, Brazil and Ecuador, all in their summer season, are experiencing high spread of the virus. As social distancing guidelines ease in Washington State over the coming months, it’s possible we’ll see a resurgence of the virus despite warmer weather. Only time will tell.

4. COVID-19 kills at a faster rate than the flu.

We’re still in the middle of this pandemic, so it’s impossible for us to say with certainty what the death rate of COVID-19 will end up being. As it becomes clearer that some people have the novel coronavirus without symptoms, the implication is that the death rate should be lower than the one to two percent initially estimated. But it’s also becoming clear that many deaths that should have been attributed to COVID-19 have not been. Even though we cannot know for certain what the death rate of COVID-19 is, we can clearly say that it has killed more people in far shorter a time period than the flu.

The CDC estimates that in the 187 days between October 1, 2019, and April 4, 2020, 24,000-62,000 people in the U.S. died of the flu. These numbers mean that between 128 and 332 people died per day of the flu. This is a huge range, I know. The CDC uses modelling to estimate the number of flu deaths each year, so it’s not always possible to get an exact death toll.

The first known U.S. death from COVID-19, once thought to be in Kirkland, Washington, on Feb. 28, has been discovered to have occurred in the San Francisco Bay area on Feb. 6. In the 85 days between Feb. 6 and May 1, there have been 37,308 deaths directly attributed to COVID-19 by lab confirmation, equaling 439 COVID-19 deaths per day.

If we also consider deaths of cases with no lab confirmation – but who were considered probable for COVID-19 (based on symptoms, known exposure to the novel coronavirus, etc.) – there have been more than 67,000 COVID-19 deaths in the U.S. This equals 788 COVID-19 deaths per day.

This is not a perfect comparison because the CDC uses modeling to estimate the number of flu deaths per season. The COVID-19 numbers reported here are actual deaths, not based on a model. The CDC does have a COVID-19 death forecast, but it changes based on the data, including when Stay Home orders are lifted. You can find it here:

Let’s look at just Skagit County now. The 2019-2020 flu season, which has now come to a close, resulted in just one death in Skagit County. But COVID-19 has been another story. Skagit County’s first diagnosed COVID-19 case occurred on March 10. Just 11 days later, we sadly lost our first person to COVID-19. And since then, we’ve lost 13 Skagitonians to COVID-19, more than doubling the death count of the worst flu season in recent years. While 13 people isn’t a huge number, the families and friends of those 13 people lost huge parts of their worlds to this virus. We don’t want more people experiencing the pain of such a loss. It’s safe to assume that this death toll would be higher without the “Stay Home, Stay Healthy” order; look at the death rate in Sweden, which has not instituted social distancing guidelines, versus the other Nordic nations that have.

It’s likely the number of reported COVID-19 deaths is underestimated, and likely significantly underestimated. The CDC has begun estimating the burden of COVID-19 deaths by looking at the number of excess deaths from what would be expected. More information on that can be found here:

5. COVID-19 does not have a vaccine.

Influenza is a long-known, well-studied virus. There are vaccines available for all sorts of strains of the virus, and a well-established supply chain ensures enough doses are available for each new flu season. While some years the vaccine is less effective than other years, people who get the vaccine and still get the flu generally have a milder case of the illness than unvaccinated people.

Of course, not everyone gets vaccinated, sometimes because of personal choice, sometimes because of health conditions that make vaccination dangerous, sometimes because it’s easy to let things slip by unnoticed. The CDC estimates that right around 60% of Americans, give or take a few percentage points, get the flu vaccine each year. The more people who get the vaccine, the fewer people the virus can infect and the slower the spread.

There is no vaccine available for the novel coronavirus. Even if you want it, you can’t get it. In the past, vaccines for new viruses took 10 or more years to develop. Scientists are working hard to have one available sooner than that, maybe even within a year or so. But until then, this virus will spread, infecting millions and killing hundreds of thousands around the world.

The only defense we have against this virus is to limit the spread ourselves. This means washing our hands often and using hand sanitizer when we can’t. It means avoiding crowds and only going out when we absolutely need to, wearing a mask in public, and staying at least six feet away from non-household members. As businesses start to open back up, it may be tempting to forget social distancing, but that is likely to lead to a resurgence of the virus, meaning we’ll have to shut down all over again. So take precautions and limit your trips out. It’s not easy and it’s not fun, but it saves lives.

It could even save your life.