The novel coronavirus that causes COVID-19 has led to over half a million confirmed cases in the U.S. alone.
For comparison, in the U.S. alone, the flu (also known as influenza) has caused about 38 million illnesses, 390,000 hospitalizations and 23,000 deaths in the 2019-2020 season, according to the Centers for Disease Control and Prevention (CDC).
While similar to the flu, COVID-19 is also distinct from the flu in several ways. However, we don’t have all the information we need to make a truly informed contrast between the two illnesses. That’s because the flu is well-studied and understood, while the novel coronavirus has never been seen before.
"Despite the morbidity and mortality with influenza, there's a certainty … of seasonal flu," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said in a White House press conference on January 31. "I can tell you all, guaranteed, that as we get into March and April, the flu cases are going to go down. You could predict pretty accurately what the range of the mortality is and the hospitalizations [will be]. The issue now with [COVID-19] is that there's a lot of unknowns."
Both seasonal flu viruses (which include influenza A and influenza B viruses) and COVID-19 are contagious viruses that cause respiratory illness, and the symptoms of flu are well understood. They include fever, cough, sore throat, muscle aches, headaches, runny or stuffy nose, fatigue and occasionally vomiting and diarrhea, according to the CDC.
While flu symptoms often come on suddenly, most people who get the flu will recover in less than two weeks. However, the flu sometimes causes complications, including pneumonia.
When it comes to COVID-19, the full picture of disease symptoms and severity has yet to be fully understood, with symptoms ranging from mild to severe. These COVID-19 symptoms include fever, cough, and shortness of breath along with fatigue, muscle aches, headache, sore throat, abdominal pain and even nausea or diarrhea. There is a less common symptom as well: loss of smell.
The onset of flu symptoms is more rapid than the onset of COVID-19 symptoms. Some people with COVID-19 may only experience symptoms mildly or not at all, while not everyone with the flu will have a fever.
There are approximately 1,997,321 cases of COVID-19 worldwide, with 609,685 cases in the U.S. as of Apr. 15, 2020 (according to the Coronavirus COVID-19 Global Cases map developed by the Johns Hopkins Center for Systems Science and Engineering).
Meanwhile, the flu infects an estimated 1 billion people worldwide, with 9.3 million to 45 million cases in the U.S. per year.
The death rate from seasonal flu is typically around 0.1% in the U.S., according to LiveScience.
Though the death rate for COVID-19 is unclear, most research suggests it is higher than that of the seasonal flu. A report published March 13 in the journal Emerging Infectious Diseases estimated that, as of Feb. 11, the death rate from COVID-19 was 12% in Wuhan, 4% in Hubei Province and 0.9% in the rest of China. The death rate appears to vary by location and age, among other factors. According to the New York Times, the fatality rate may be greater than 1%.
Data indicates that about 20% of people with COVID-19 experience severe illness requiring hospitalization, oxygen and even ventilation.
Scientists use a measure known as the “basic reproduction number,” or R0 (R-nought), in order to determine how easily a virus spreads. R0 is an estimate of the average number of people who catch the virus from one infected person. According to the New York Times, the flu has an R0 value of about 1.28, meaning that each infected person infects about one other person.
Researchers are still investigating the R0 value of COVID-19. However, preliminary studies indicate an R0 value between 2 and 3, with the New England Journal of Medicine placing it at about 2.2, meaning that each infected person spreads the virus to at least 2 or 3 people.
Both the flu and COVID-19 can be spread from person to person through droplets in the air from an infected person coughing, sneezing or talking. Both can also be spread by an infected person for several days before their symptoms appear.
However, it appears that COVID-19 might be spread through the airborne route. This means that infected droplets in the air may spread the disease to others even after the infected person is no longer nearby.
COVID-19 has an incubation period (the amount of time the virus is present in a person before causing symptoms) of 2 to 14 days, while the flu’s incubation is 1 to 4 days.
Neither the flu nor COVID-19 is treatable with antibiotics, as antibiotics only work on bacterial infections. Instead, both are treated by addressing symptoms, like reducing fever. In severe cases, infected people may need to be hospitalized and supported with measures such as mechanical ventilation.
Antiviral medications address symptoms and occasionally shorten how long the flu lasts. They are currently being tested, along with other drug therapies, to see if they can address symptoms.
While no vaccine is available for COVID-19 at this time, one is in progress. However, flu vaccines are available every year to help prevent some of the most dangerous types and reduce the severity of the flu.
While COVID-19 and the flu do share some similarities, it is important to remember that protection against them is similar and rests in washing your hands vigilantly for twenty seconds at a time.