They spread in similar ways and share many of the same symptoms — but the flu and the coronavirus have key differences.
While President Donald Trump has repeatedly compared the coronavirus to seasonal influenza, experts say the coronavirus can be more insidious for several reasons: It is more contagious; it has a higher mortality rate; and, unlike the flu, currently there is no vaccine for it.
"We have much more capability and expertise to treat and prevent the flu that we don't yet have with coronavirus," said Dr. Sankar Swaminathan, virologist and chief of infectious diseases at the University of Utah Health.
That's because researchers are still learning about the coronavirus and the illness it causes, COVID-19. While the rapid spread of the virus has been alarming — with more than 132,000 cases worldwide already and nearly 5,000 deaths — the good news is that about 80 percent of those who catch it only have mild symptoms, and tens of thousands of people have recovered.
The bad news is the other 20 percent get the illness severe enough to require hospitalization, and the mortality rate appears to be significantly higher than that of the flu, which typically only kills a tenth of 1 percent of the people it infects each year.
But the flu still infects many more people: On Friday, the Centers for Disease Control and Prevention announced there have been at least 36 million illnesses, 370,000 hospitalizations and 22,000 deaths from the flu in the U.S. so far this season. Of the deaths, 144 were children.
With the flu, both young children and the elderly are at risk for developing fatal complications; with the coronavirus, children seem to have little to no symptoms at all, puzzling experts. In China, where the outbreak started, children comprised just 2.4 percent of all reported cases, a report from last month found. Individuals with underlying conditions and/or people over 60 are at the greatest risk for getting complications from the coronavirus, with the risk increasing with age.
Experts are still trying to calculate precisely what the mortality rate of the coronavirus is, but it appears to be many times higher than that of the flu.
"If you get the flu, 99.9 percent of people are going to be just fine."
"A lot of people have been trying to underplay this, saying, 'Oh, it's the corona flu,'" said Dr. Daniel Griffin, a Columbia University infectious diseases specialist. "But if you get the flu, 99.9 percent of people are going to be just fine."
The flu and the coronavirus look alike in many ways. Both cause fever and cough, and both can lead to pneumonia (with the coronavirus, shortness of breath is another common symptom). They are also transmitted in the same manner: through respiratory droplets, the particles expelled when someone who is sick coughs, sneezes or breathes. It can also be transmitted through contact: shaking hands with someone who has touched their face, and then touching your own face, for example.
While the flu follows a distinct seasonal pattern every year, no one knows yet what the coronavirus pattern will look like.
Efforts to develop a vaccine for it are underway, but nothing exists to prevent it at the moment. With the flu, a vaccine is manufactured each year to keep up with the constantly mutating genes of the flu strains. Those who catch the flu have some immunity against catching the same strain again — something that is not yet possible with the coronavirus.
"This is a completely novel virus that we have zero pre-existing immunity to, so essentially every person is vulnerable."
"We have the worst-case scenario, which is this is a completely novel virus that we have zero pre-existing immunity to, so essentially every person is vulnerable — which makes it possible for this worldwide pandemic to occur," Swaminathan said. It is not yet known if those who have been infected once develop immunity against it in the future.
What makes the coronavirus extra tricky to tamper down, experts say, is its incubation period, or the amount of time between catching the illness and the start of symptoms. An infected individual can go anywhere from one to 14 days before symptoms start appearing, with symptoms most commonly appearing around five days after exposure, the World Health Organization believes.
If diagnosed early, there's an antiviral medication, Tamiflu, which can help shorten the symptoms of the flu. Nothing has yet been approved to treat the coronavirus, although doctors have similar recommendations for mild cases of it as they do for mild flu cases: rest, hydrate and take fever-reducing medicines such as Tylenol.
The experts' advice for limiting the spread of both illnesses is the same: practice proper hand-washing, don't touch your face and stay home if you feel sick.
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They urged everyone to get a flu shot if they have not already, even though the flu shot won't protect you against the coronavirus because the two are from different families of viruses.
Still, getting the flu vaccine could keep people out of the hospital — something desperately needed.
"If we can prevent one more person from coming to our emergency rooms to be evaluated for a serious respiratory illness, we would take that," Swaminathan said.