The new coronavirus outbreak has made headlines in recent weeks, but there’s another viral epidemic hitting countries around the world: flu season. But how do these viruses compare, and which one is really more worrisome?
So far, the new coronavirus has led to more than 100,000 illnesses and more than 3,000 deaths worldwide. But that’s nothing compared with the flu, also called influenza. In the U.S. alone, the flu has caused an estimated 34 million illnesses, 350,000 hospitalizations and 20,000 deaths this season, according to the Centers for Disease Control and Prevention (CDC).
That said, scientists have studied seasonal flu for decades. So, despite the danger of it, we know a lot about flu viruses and what to expect each season. In contrast, very little is known about the new coronavirus and the disease it causes, dubbed COVID-19, because it’s so new. This means COVID-19 is something of a wild card in terms of how far it will spread and how many deaths it will cause.
“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 Jan. 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],” Fauci said. “The issue now with [COVID-19] is that there’s a lot of unknowns.”
Scientists are racing to find out more about COVID-19, and our understanding of the virus that causes it and the threat it poses may change as new information becomes available. Based on what we know so far, here’s how it compares with the flu.
Symptoms and severity
Both seasonal flu viruses (which include influenza A and influenza B viruses) and COVID-19 are contagious viruses that cause respiratory illness.
Typical flu symptoms include fever, cough, sore throat, muscle aches, headaches, runny or stuffy nose, fatigue and, sometimes, vomiting and diarrhea, according to the CDC. Flu symptoms often come on suddenly. Most people who get the flu will recover in less than two weeks. But in some people, the flu causes complications, including pneumonia. So far this flu season, about 1% of people in the United States have developed symptoms severe enough to be hospitalized, which is similar to the rate last season, according to data from the CDC.
With COVID-19, doctors are still trying to understand the full picture of disease symptoms and severity. Reported symptoms in patients have varied from mild to severe, and can include fever, cough and shortness of breath, according to the CDC.
In general, studies of hospitalized patients have found that about 83% to 98% of patients develop a fever, 76% to 82% develop a dry cough and 11% to 44% develop fatigue or muscle aches, according to a review study on COVID-19 published Feb. 28 in the journal JAMA. Other symptoms, including headache, sore throat, abdominal pain, and diarrhea, have been reported, but are less common.
Another recent study, considered the largest on COVID-19 cases to date, researchers from the Chinese Center for Disease Control and Protection, analyzed 44,672 confirmed cases in China between Dec. 31, 2019 and Feb. 11, 2020. Of those cases, 80.9% (or 36,160 cases) were considered mild, 13.8% (6,168 cases) severe and 4.7% (2,087) critical. “Critical cases were those that exhibited respiratory failure, septic shock, and/or multiple organ dysfunction/failure,” the researchers wrote in the paper published in China CDC Weekly.
It’s important to note that, because respiratory viruses cause similar symptoms, it can be difficult to distinguish different respiratory viruses based on symptoms alone, according to WHO.