Distinguishing Flu from COVID-19 Will Be One of Autumn's Most Important Issues

Autumn has arrived and winter is approaching, so alarm bells are ringing: influenza viruses cause flu. We are worried about the combination of the globally widespread COVID-19 with the flu that emerges with the change of season.

The American Academy of Pediatrics strongly recommends that children aged 6 months and older receive, by the end of October at the latest, a flu vaccine. Experts stated that age-appropriate, licensed intranasal or injectable flu vaccines are suitable. Scientists explaining some changes to the flu vaccines prepared for 2020-2021 said: “Vaccines prepared for children are of the type we call quadrivalent. These vaccines help the body respond to three new influenza virus strains by producing an acquired immune response. Studies show that, in the United States alone last year, 188 children and adults younger than 19 died from influenza flu. The main point to emphasize here is that approximately 80% of the children who died had not received the flu vaccine. These findings are striking, but this year we face a much more dangerous situation: COVID-19 disease caused by the novel coronavirus. The most challenging point with flu and COVID-19 will be being unable to distinguish them. However, we should note that there is no reason why people diagnosed with COVID-19 who have recovered should not receive a flu vaccine”.

- Related topic: Flu and Pneumonia Vaccines – Do They Protect Against Coronavirus, and Who Should Receive Them and When? (Türkçe)

COVID-19 and flu are very difficult to distinguish

Many scientists continue researching how to distinguish COVID-19 from flu and determine effective treatments. What do the data obtained so far tell us?

Research results suggest that patients diagnosed with COVID-19 are more likely than flu patients to report fever, cough, gastrointestinal (stomach-intestine) complaints and other clinical symptoms at diagnosis, with a higher likelihood, but show that the two patient groups have many overlapping clinical symptoms.

A study comparing children diagnosed with COVID-19 and flu

The study included 315 children diagnosed with COVID-19 between 25 March and 15 May and 1402 children diagnosed with seasonal influenza A and influenza B flu between 1 October 2019 and 6 June 2020. The two patient groups had similar rates of hospitalization, intensive care treatment and need for a ventilator. Children hospitalized because of COVID-19 were older than those hospitalized because of flu; 65% of children hospitalized with a coronavirus diagnosis had another health problem, whereas this rate fell to 42% in patients with flu.

The researchers stated that fever and cough were the symptoms reported most frequently in both groups, adding that patients presenting with fever, diarrhea, vomiting, headache, muscle pain or chest pain were mostly diagnosed with COVID-19.

Doctors should use a combination of symptoms, examination and tests to distinguish the two diseases

Both flu and COVID-19 can be diagnosed using PCR tests and are viral diseases. For viral pneumonia caused by COVID-19, lung tomography is also a highly effective diagnostic tool.

As we are now entering the seasonal flu season, both COVID-19 and flu should be considered in patients presenting to hospital with fever, diarrhea, vomiting, headache, muscle pain, chest pain or reduced appetite. Doctors may therefore request PCR tests for both viral diseases. However, because social isolation and mask rules have been widely followed this year, seasonal flu may affect fewer people than in previous years.

Questions about the pneumococcal vaccine

The bacterium called pneumococcus is known to cause pneumonia, particularly in people over 65, and other infections such as meningitis and middle ear infections. For this reason, the pneumococcal vaccine is recommended for people over 65 to protect against these infections.

Neither the flu vaccine nor the pneumococcal vaccine can be said to be more important than the other. However, it is safe to say that flu caused by the influenza virus occurs much more frequently than pneumonia caused by pneumococcal bacteria.

There are, however, two major misconceptions about the pneumococcal vaccine:

• First, it is assumed that the pneumococcal vaccine protects against all pneumonias, which is not true. This vaccine protects only against pneumonia caused by pneumococcal bacteria, not pneumonia caused by other bacteria or viruses.
• Second, the pneumococcal vaccine does not protect against pneumonia caused by COVID-19 either. Claims of cross-protection are all either rumors or findings from research with weak evidence.

Vaccinating the whole population against influenza or pneumococcus is neither necessary nor possible. The new flu vaccine to be used this year has not yet entered the market. Children already receive the conjugate pneumococcal vaccine 3 times by the age of 1. Flu and pneumococcal vaccines should therefore be given to people at risk on the advice of their family physicians or the doctors following them. Family medicine practices are the most appropriate and safest way to access vaccines.

Conclusion

If people with the above symptoms require hospitalization, we will continue testing for flu and COVID-19 before or during admission, providing fluids and oxygen, and deciding on treatment protocols according to clinical factors such as changes in vital signs. At this point, it will be extremely important to ensure that all children, healthcare workers, people over 65 and people with chronic disease on their doctors' advice receive a flu vaccine. The new flu vaccines planned for 2020-2021 are not yet available on the market but will arrive soon. The appropriate time for flu vaccination is by the end of October. In addition, measures such as wearing a mask, social distancing and hand hygiene must be maintained to prevent the spread of many viruses, including COVID-19 and flu.

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