From symptoms alone, there’s really no good way to tell the two apart
The viruses that cause the flu and COVID-19 are not the same, and the diseases are different, too, but they have a lot in common. The flu is caused by several different strains of virus. Influenza A and B are the ones that spur flu season. COVID-19 is caused by a virus called SARS-CoV-2, which was first identified in late 2019.
The Centers for Disease Control and Prevention says symptoms for both flu and COVID-19 can range from mild to severe. Both illnesses can cause fatigue, body aches, fever, chills, coughing or headache. Shortness of breath, runny nose and loss of taste or smell are more common with COVID-19.
From symptoms alone, there’s really no good way to tell flu apart from COVID-19 infection. Both spread in similar ways. Both viruses multiply in the upper respiratory tract. When people who are infected cough or speak, virus-laden respiratory droplets are expelled. Someone who breathes in those particles can get sick.
But SARS-CoV-2 is more contagious than the flu viruses, partly because it’s new to humans. Because flu has been around for so long, most of us are partially immune either by vaccination or through previous exposures to flu, which is why the vast majority of us don’t get very sick.
Both viruses can be spread by infected people before they have symptoms. The CDC says a person infected with COVID-19 could be contagious about two days before having symptoms compared to one day for most people with the flu. And people with COVID-19 could be contagious longer from the onset of symptoms – at least 10 days as opposed to seven days with the flu.
While both diseases can be deadly, the coronavirus has caused much more devastation since it came on the scene. During the 2018-2019 flu season, influenza caused 34,157 deaths in the United States, according to CDC estimates. In 2020, COVID-19 was the underlying cause of 345,323 deaths in the U.S., according to CDC data.
Also, the diseases don’t target people equally. Probably the major difference between flu and COVID is the behavior of the disease in very young children. Very young children seem to be somewhat less likely to become ill with COVID. Flu, on the other hand, actually tends to make very young children very sick.
Both viruses also pose a serious risk to the heart and brain. A 2018 study in the New England Journal of Medicine found the risk of heart attack was six times higher in the week after someone was diagnosed with the flu. With COVID-19, heart damage can occur. Flu has been associated with a higher risk of stroke, as has COVID-19.
Both the flu and COVID-19 trigger similar reactions in the body. Each illness sensitizes or revs up the immune system, triggering inflammatory responses as the body’s defense mechanisms try to eradicate the invaders. Both viruses also can cause platelets to become extra sticky, leading to blood clots.
Luckily, similar measures protect against both diseases. Wearing a mask and physical distancing helps stop the spread of respiratory viruses. So does frequent hand-washing for at least 20 seconds.
YOU NEED BOTH VACCINES
And then there are vaccines. The vaccines help reduce a person’s risk of getting sick, especially with the severe illness that can cause hospitalization and death. The CDC recommends almost everyone get a flu shot before flu season, normally in the fall. For people with heart disease, the flu vaccine can lower the risk of dying from heart problems and any other cause, according to research published in March in the Journal of the American Heart Association.
Flu strains evolve, so the vaccines are reformulated every year. This year’s vaccines are designed to protect against the four flu viruses most likely to spread during the upcoming season.
But confusion persists. According to a recent online survey of 1,000 U.S. adults conducted for the American Heart Association, 27 percent incorrectly believed you can get the flu from the vaccine. And 12 percent thought you can’t get both a COVID-19 and flu vaccine at the same time. But you can, the CDC says. And you do need both.
The COVID-19 vaccine isn’t going to give you any cross-protection from the flu, and the flu vaccine isn’t going to protect you from COVID at all. Together, they offer a bonus layer of protection because any time you get one infection, that weakens your body and then makes you more susceptible to other infections.
Can I get the flu and COVID-19 vaccines at the same time?
When COVID-19 vaccines were first rolling out in the U.S., the Centers for Disease Control and Prevention recommended waiting 14 days between the shots and other immunizations as a precaution. But the agency has since revised its guidelines and says the wait is unnecessary.
The CDC and other health experts point to past experience showing that vaccines work as they should and any side effects are similar whether the shots are given separately or in the same visit.
“We have a history of vaccinating our kids with multiple vaccines,” flu specialist Richard Webby of St. Jude Children’s Research Hospital told Emma H. Tobin of the Associated Press.
Staying up to date on all vaccinations will be especially important this year, experts say.
Since people were masked and staying home, last year’s flu season barely registered. This year, it’s unclear how intense the flu season will be with more places reopening.
“The worry is that if they both circulate at the same time, we’re going to have this sort of ‘twin-demic,’” Webby says. “The concern with that is that it’s going to put extra strain on an already strained health care system.”
The CDC recommends an annual flu vaccine for everyone six months and older, and says ideally everyone should be vaccinated by the end of October. It takes 10 to 14 days for the flu vaccine to take full effect so if you wait until the flu begins circulating, your body may not have time to build up protection. Vaccine options vary by age but include several types of shots or a nasal spray version.