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The fact that the novel coronavirus appeared in the middle of flu season has prompted inevitable comparisons. Is COVID-19, the disease caused by the virus, pretty much similar to the flu or does it pose a far greater threat? 

Although there are still many unknowns about COVID-19, there is some solid information from researchers that sheds light on some of the similarities and differences at this time.

Fever, dry cough, fatigue and shortness of breath. These are the most frequent symptoms of COVID-19. Some patients might develop aches and pains; just 5 percent get the sniffles, according to 

 — indicating that COVID-19 is not usually an upper respiratory infection. 

. The Centers for Disease Control and Prevention says that anyone who is experiencing these symptoms and who has been in direct contact with a confirmed COVID-19 patient, or who lives in an area where cases are circulating, should 

Flu and coronavirus are both thought to be spread primarily through close contact with droplets expelled from the nose and mouth of a sick person. So you can become infected by direct contact such as 

kissing but also by close talking with someone who's infected.

 The CDC recommends keeping a physical distance of about six feet away from others. You can also pick up flu or coronavirus if you touch a tabletop or phone that was coughed on, but not disinfected, in the past few 

Data from China shows that each coronavirus case seems to infect around 2 to 2.5 additional people. That's higher than flu. The average patient spreads the flu virus to about 

New research suggests that the higher number of infections per coronavirus patient may be related to the frequency of presymptomatic transmission — when people who have been infected are not yet showing symptoms but in fact could be contagious. An analysis of data from China 

 percent of cases were likely caused by people spreading coronavirus before they started coughing and feeling achy. 

By contrast, flu is most contagious in the three or four days after symptoms begin, according 

It's also possible that coronavirus can be transmitted by other methods. Researchers are trying to determine, for example, if tiny droplets can stay suspended in the air in contagious doses, or if fecal matter can be a source of infection.

 — which ranges from having a fever and a cough to low-grade pneumonia. It might still be miserable, but you can heal up on your couch at home.

Data from China shows that 20 percent of COVID-19 patients, though, are serious enough to get sent to the hospital. That's about 10 times more often 

. Even though a great many people are hospitalized for the flu — the preliminary data for the 2018-19 flu season is nearly 

 — the rate of hospitalization is far lower: 

 percent percent of cases, according to the CDC.

For coronavirus, "what's particularly concerning are the number of people who are progressing to need hospital level care and then eventually critical care and who are dying, especially at the extremes of [older] age," says 

, an epidemiologist at University of Texas in Austin's Dell Medical School.

People who are over 60 and who have other health problems are more at risk

of severe illness and hospitalization — for both COVID-19 and flu. 

Once a patient with a serious case of coronavirus is hospitalized, the average stay is 11 days, 

 based on January data from Wuhan — about twice as long as the 5-to-6 day average stay for flu.

The additional days mean additional stresses on the health-care system. "To take care of intensive, really unwell people can often require two to three medical staff at one time, all in protective gear, for hours and hours," says

, director of the World Health Organization's Health Emergencies Program.

That's a big strain on our nurses and doctors and hospitals, and it's overlapping with flu season, which generally ends by May. From early October through the beginning of March, the CDC estimates that between 

What percentage of the population will get each virus?

There are years of data that can answer that question for influenza. In the U.S., for example, in recent years about 8.3 percent of the total population get sick from flu each season, 

; including people who carry flu virus but show no symptoms, that estimate ranges to up to 20 percent. 

Nobody knows what percentage of the population will eventually contract coronavirus. But there are some educated guesses. Since this is a new disease and there's no vaccine and no established immunity from past cycles, experts believe everyone is susceptible. 

 from researchers at the University of Hong Kong and Harvard, published in 

, predicted that globally, "at least one-quarter to one-half of the population will very likely become infected, absent drastic control measures or a vaccine."

 released March 16 from Imperial College of London predicted a 

 in which 81 percent of the U.S. population could get infected over the next few months, if no actions were taken to slow or contain the spread of the virus. Predictions from models like this appear to have 

 to implement social distancing measures to combat the virus's spread.

To come up with better data for COVID-19 infection rates, researchers are doing blood tests in China to see how many people have been infected in a place where the epidemic appears to have been successfully suppressed through efforts such as lockdowns, contact tracing and an increase in hospital capacity. 

Initial data shows that coronavirus is deadlier. In the U.S., seasonal flu kills 

 people (0.1 percent) who get sick from it — the death toll last season was more than 34,000. Worldwide, an estimated 

By contrast, COVID-19 is currently estimated to kill at least 10 people per thousand infected (1 percent). "It's about 10 times more lethal than the seasonal flu," said 

, director of the National Institutes of Allergy and Infectious Disease, in congressional testimony on March 11.

More data is needed to assess the COVID-19 death rate, including detailed figures on how many cases present with mild symptoms or no symptoms at all. So far, COVID-19 has killed around 10,000 people worldwide how many people worldwide — and around 200 in the U.S. But infectious disease specialists warn that, if coronavirus spreads widely in the U.S., the numbers could rise quickly.

"It does have the potential to be just as bad, if not worse, in terms of the overall number of deaths and severe cases as seasonal flu," says 

Rest and supportive care are the common treatments for both 

 and for coronavirus cases that don't require hospitalization.

For flu, which has been studied intensively, doctors have some additional tools to fight it, says 

, an infectious disease fellow at the UPMC Children's Hospital of Pittsburgh. A drug called Tamiflu aims to stop the flu virus from replicating in the body and can lessen the severity of symptoms. Other treatments that prime the body's

There are no approved treatments for COVID-19 yet, though researchers are racing to see if pills for other ailments could work against coronavirus, and to develop specific therapies that would lessen symptoms and hasten recovery. 

Existing medications are being evaluated in the U.S., China and other countries. "It is likely that we will know if they work in the next several months," said Dr. Fauci, director of the NIAID, in 

. Drugs under consideration include remdesevir, an experimental drug originally developed for Ebola, and an anti-malarial called chloroquine, 

For vaccines that could prevent COVID-19, Dr. Fauci said it will take at least a year to a year and a half for a vaccine to be available to the public. Vaccine development requires a 

 of human trials. "It will take three or four months to determine if [a vaccine option] is safe," he said, and at least another eight months to gauge whether it's effective. The first U.S. vaccine clinical trials started on Monday, the 

Modern flu vaccines were first developed 

 and protected U.S. troops against the flu during World War II. A new vaccine is developed each year to combat the 

. This flu season, the CDC says that around 160-170 

 were shipped out — enough to cover about half the U.S. population.

. In the U.S., each flu season varies, but the number of new flu cases 

 between December and February, and tail off by the month of May. 

Researchers think it has to do with how people spend more time outside when it's warmer, and how higher heat and humidity can cause some viruses to decay more quickly. They're also studying how the immune system may 

, an adviser to WHO, says don't count on a similar pattern for COVID-19, which is thriving in warm, tropical places: "It's roaring in Singapore. It's not flu season in Singapore. It's roaring in the southern part of China. It's not flu season." 


Researchers will only know if coronavirus follows flu patterns by seeing whether infections decline as the seasons change. There's the possibility that it won't, so in the meantime, Aylward thinks hospitals should prepare as though COVID-19 is here to stay as a year-round health threat.


Health

COVID-19

Pien Huang

Author

There are definitely similarities between COVID-19, caused by the coronavirus, and influenza. But there are critical differences as well, including the death rate. 

How the novel coronavirus and the flu are alike — and different

Go Deeper.

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