COVID-19 vs flu: How to tell the difference between the two respiratory viruses

Influenza and COVID-19 have very similar symptoms

COVID-19 vs flu: How to tell the difference between the two respiratory viruses
Close-up shot hand of nurse holds medical test tubes for coronavirus – Photo: File photo/EL UNIVERSAL
English 26/09/2020 12:45 AP Mexico City Actualizada 12:45

Leer en español

How can I tell the difference between the flu and COVID-19?

It is impossible to tell without a test. Influenza and COVID-19 have such similar symptoms, you may need to get tested to know what is making you miserable.

Body aches, sore throat, fever, cough, shortness of breath, fatigue, and headaches are symptoms shared by the two.

According to the World Health Organization, both COVID-19 and influenza "cause respiratory disease, which presents as a wide range of illness from asymptomatic or mild through to severe disease and death"

One difference? People with the flu typically feel sickest during the first week of illness. With COVID-19, people may feel the worst during the second or third week, and they may be sicker for a longer period.

Recommended: How to boost your immune system

Another difference: COVID-19 is more likely than the flu to cause a loss of taste or smell. But not everyone experiences that symptom, so it is not a reliable way to tell the viruses apart.

That leaves testing, which will become more important as flu season ramps up this fall in the Northern Hemisphere. Doctors will need to know test results to determine the best treatment.

It is also possible to be infected with both viruses at the same time, said Dr. Daniel Solomon, an infectious diseases expert at Brigham and Women’s Hospital and Harvard Medical School in Boston.

Whether you get tested for one or both viruses may depend on how available tests are and which viruses are circulating where you live, he said.

“Right now we are not seeing community transmission of influenza, so widespread testing for the flu is not yet recommended,” Solomon said.

Both the flu and coronavirus spread through droplets from the nose and mouth. Both can spread before people know they are sick. The flu has a shorter incubation period — meaning after infection it can take one to four days to feel sick — compared to the coronavirus, which can take two to 14 days from infection to show symptoms.

On average, COVID-19 is more contagious than flu. But many people with COVID-19 do not spread the virus to anyone, while a few people spread it to many others. These “superspreader events” are more common with COVID-19 than flu, Solomon said.

Another difference mentioned by the WHO is that , while children are important drivers of influenza virus transmission in the community, initial data for COVID-19 shows children are less affected than adults and  "further preliminary data from household transmission studies in China suggest that children are infected from adults, rather than vice versa."

Preventing the flu starts with an annual flu shot tailored to the strains of the flu virus that are circulating. Health officials would like to see record numbers of people get flu shots this year so hospitals are not overwhelmed with two epidemics at once.

There is no vaccine yet for COVID-19, although several candidates are in the final testing stages.

Precautions against COVID-19 — masks, social distancing, hand-washing — also slow the spread of the flu, so health officials hope continued vigilance could lessen the severity of this year’s flu season.

The WHO says that since both viruses are transmitted by contact, droplets, and fomites, the same public health measures are important actions everyone can take to prevent infection.