Fortress Influenza and COVID-19 Ag Rapid Test

14 December, 2020

As we are now in the midst of the influenza (flu) season and COVID-19 continues to spread, Fortress Diagnostics have launched a new rapid test that uses a single swab sample to test for both Influenza & COVID-19.

  • Why is it important to differentiate between the two? Both cause respiratory disease, yet there are important differences between the two viruses and how they spread. This has important implications for the public health measures that can be implemented to respond to each virus as well as how quickly a patient treatment is decided to prevent severe illness or mortality.
  • How are COVID-19 and influenza viruses similar? COVID-19 and influenza viruses have a similar disease presentation. That is, they both cause respiratory disease, which presents as a wide range of illness from asymptomatic or mild through to severe disease and death.  Both viruses are transmitted by contact, droplets and fomites.

Signs and Symptoms - Similarities:

Both COVID-19 and flu can have varying degrees of signs and symptoms, ranging from no symptoms (asymptomatic) to severe symptoms. Common symptoms that COVID-19 and flu share include:

  • Fever or feeling feverish/chills
  • Cough
  • Shortness of breath or difficulty breathing
  • Fatigue (tiredness)
  • Sore throat
  • Runny or stuffy nose
  • Muscle pain or body aches
  • Headache
  • Some people may have vomiting and diarrhoea

Transmission in the first 3-5 days of illness, or potentially pre-symptomatic transmission –transmission of the virus before the appearance of symptoms – is a major driver of transmission for influenza. In contrast, while we are learning that there are people who can shed COVID-19 virus 24-48 hours prior to symptom onset, at present, this does not appear to be a major driver of transmission.
The speed of transmission is an important point of difference between the two viruses. Influenza has a shorter incubation period and a shorter serial than COVID-19 virus. The serial interval for COVID-19 virus is estimated to be 5-6 days, while for influenza virus, the serial interval is 3 days. This means that influenza can spread faster than COVID-19.

How are COVID-19 and influenza viruses different?

The reproductive number – the number of secondary infections generated from one infected individual – is understood to be between 2 and 2.5 for COVID-19 virus, higher than for influenza. However, estimates for both COVID-19 and influenza viruses are very context and time-specific, making direct comparisons more difficult. 

Children are important drivers of influenza virus transmission in the community. For COVID-19 virus, initial data indicates that children are less affected than adults and that clinical attack rates in the 0-19 age group are low.

People at high Risk

Those most at risk for severe influenza infection are children, pregnant women, elderly, those with underlying chronic medical conditions and those who are immunosuppressed. For COVID-19, our current understanding is that older age and underlying conditions increase the risk for severe infection.


 Both COVID-19 and influenza illness can result in severe illness and complications. Those at highest risk include:

  • Older adults
  • People with certain underlying medical conditions
  • Pregnant people

Why Fortress Diagnostics Combo Test?

In-vitro diagnostics (IVDs) are among the most common and widely used clinical tests that health care providers rely on to detect diseases or monitor a person’s overall health. Since patients receive medical care based on the diagnostic results, the accuracy of these tests is crucial. Diagnosis at an early stage will prevent further infection and determine effective treatment to avoid illness and mortality.

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