IN THE KNOW: More similarities than differences between flu and COVID-19

MANILA, Philippines — Influenza and COVID-19, both infectious respiratory diseases, share similar symptoms and can even be contracted by a person at the same time, making it tricky to determine the infection by symptoms alone.

According to the World Health Organization (WHO), flu, which is caused by the influenza virus, and COVID-19, caused by SARS-CoV-2, spread similarly via droplets and aerosols when an infected person coughs, sneezes, speaks, sings or breathes.

People can also contract both COVID-19 and influenza by touching contaminated surfaces and then touching their eyes, nose or mouth.

The United States’ Centers for Disease Control and Prevention (CDC) lists the following shared symptoms for flu and COVID-19: fever or having chills, cough, shortness of breath or difficulty breathing, fatigue, sore throat, runny or stuffy nose, muscle pain or body aches, headache, vomiting and diarrhea and change in or loss of taste or smell (although this is more frequent with COVID-19).

However, symptoms may develop longer after infection for those with COVID-19 than those who have flu, the CDC said.

A person with COVID-19 typically shows symptoms five days after being infected, while a person with flu can experience symptoms one to four days after infection.

Those with COVID-19 can also be contagious for a longer time than people with flu, who are contagious for only about a day before they show symptoms.

Health experts from the WHO had said that some may have few symptoms for flu or COVID-19 depending on one’s immunity level.

The Johns Hopkins University, meanwhile, said both illnesses can be asymptomatic and symptoms may range from mild to fatal. Flu and COVID-19 may also lead to pneumonia.

Cooler weather and lower humidity are also key factors in the spread of viruses, the US National Institutes of Health said in its January 2022 newsletter. It quoted health experts who said cold and flu viruses survive better and become more transmissible during winter.

Likewise, health experts had said that preventive measures are similar for the two diseases, namely washing of hands, wearing of masks, maintaining physical distancing and staying in well-ventilated areas.

A preliminary study in The University of Hong Kong (HKU) showed that Omicron thrives in airways, where it multiplies itself 70 times more quickly, compared to the Delta variant. Omicron, however, replicates 10 times more slowly in lung tissues, which might contribute to less severe illness. But the peer review for the formal report of the study has yet to be completed.

In the Philippines, influenza-like illnesses increased by 30 percent last year. From Jan. 1 to Nov. 13, there were 71,708 influenza-like cases, up from 55,331 cases recorded during the same period in 2020, based on a surveillance report of the Department of Health.

Davao region had the most number of cases in the same period with 16,013, followed by Northern Mindanao (10,168) and Central Visayas (8,773).

Deaths due to influenza-like illnesses also rose to 831 from Jan. 1 to Nov. 13 last year, up from 577 deaths registered in the same period in 2020.

—INQUIRER RESEARCH