COVID-19 vs. flu: some similarities, key differences

COVID-19 is not the flu, but the two respiratory illnesses share many similar symptoms, complicating diagnosis as the annual flu season begins this fall.

Key differences between the two illnesses include incubation period, how the viruses infect the body, how the viruses spread, symptoms, infectious period, risks of severe infections by age groups, treatments, vaccine availability and complications from the illnesses.

Both share symptoms of fever, chills, cough, sore throat, shortness of breath, runny or stuffy nose, body aches, headache and fatigue. And in both illnesses some patients experience problems such as vomiting and diarrhea, Clarkston physician Anubhav Kanwar said.

The loss or change in the senses of smell and taste are symptoms unique to COVID-19, said Kanwar, who specializes in infectious diseases, tropical medicine and traveler’s health at Tri-State Memorial Hospital.

Both diseases can be deadly, but the flu is most lethal for the very young and those older than 65, while COVID-19 is most deadly to people older than 65.

“Children somehow do not develop severe infection,” Kanwar said of COVID-19. “Children are not at as high a risk as they are for flu.”

Both diseases are more lethal to people with underlying conditions such as a suppressed immune system, high blood pressure, asthma, Type 1 diabetes, smokers, cerebrovascular disease, liver disease, pregnant women, pulmonary fibrosis, certain blood disorders and neurologic conditions, regardless of age.

With flu season approaching, Kanwar suggests parents ask their physicians to test for both the flu and COVID-19 should their child come down with a fever and sore throat or other symptoms common to both illnesses.

Anyone who has the symptoms should also put on a mask immediately, because that will “drastically cut down on how much virus they will spread,” Kanwar said. People with symptoms should self-isolate in their homes and seek medical attention by calling their doctor in advance.

Influenza and the coronavirus are different families of virus and infect the body through different mechanisms, Kanwar said.

The flu is caused by the influenza family of viruses, and that virus infects the body by using hemagglutinin proteins to allow the virus to penetrate foreign bodies. Flu also has the enzyme neuraminidase on the surface of the virus that allows it to be released from a host cell. The enzyme is necessary for the virus to replicate itself. The protein and enzyme are used in naming a specific flu, such as H1N1.

COVID-19 comes from the coronavirus family and uses proteins called ACE receptors to infect people, Kanwar said.

Once the body acquires either virus, the time until symptoms show is also different. In the flu, symptoms show within one to four days. In COVID-19, symptoms can show within two to 14 days, but the average is five to seven days, Kanwar said.

People are infectious for different amounts of time with each virus, as well. Those with influenza can be contagious from one day before symptoms to three to four days after symptoms show. COVID-19 patients can be contagious up to three days before symptoms begin and up to 10 days after symptoms arrive in otherwise healthy patients.

Immunocompromised patients may be contagious with COVID-19 for up to 21 days after symptoms begin, Kanwar said.

Asymptomatic COVID-19 patients are also contagious. Up to 40 percent of people with COVID-19 can be asymptomatic.

The flu spreads through exhaled water droplets in the air from an infected person. The transmission of the disease can occur when someone else inhales those infected water droplets or when those droplets land on surfaces such as doorknobs and other common items, people can pick up the virus by touching those surfaces and then touching their face.

COVID-19 is also spread by infected water droplets exhaled by infected people, but the virus has an aerosolization component to it that allows it to stay in the air for up to three hours, Kanwar said. The droplets also settle on surfaces, and people can contract the virus from touching those surfaces and then touching their faces with their unclean hands.

Another difference between the two viruses is the complications. Both the flu and COVID-19 have been associated with people developing strokes and heart attacks caused by blood clots after being infected.

“But we haven’t seen the extensive clotting (with the flu) that we have seen with COVID-19,” Kanwar said.

Treatments for the diseases also differ. The flu can be treated effectively with Tamiflu and other medications recently approved by the Food and Drug Administration, Kanwar said. There are two treatments being used for COVID-19, but he said they are not very effective. The drug Remdesivir and the steroid dexamethasone have been shown to reduce fatal outcomes in COVID-19 patients.

The biggest difference between the two viruses is that there are effective vaccines for the flu, but no vaccines that have been developed and approved for COVID-19.

Still, Kanwar said he believes the Lewiston-Clarkston Valley can still defeat the pandemic by boosting its ability to test for the virus, isolating and quarantining those with the virus and doing contact tracing to identify where more testing and quarantining needs to be done.

Wells may be contacted at mwells@lmtribune.com or (208) 848-2275.