COVID-19 and influenza share a number of similarities but have key differences. Knowing how they differ will be the key to diagnosis this flu season. Get quizzed!
Coronavirus disease 2019 (COVID-19) and influenza are both contagious respiratory diseases that share many characteristics including symptoms and modes of transmission, but there are still key differences between them. Differentiating between them this year is more important than ever, for selecting testing, treatment, guidance on quarantine and precautions, and more.
Find out what you've learned since last year at this time.
Question 1. A patient presents with a cough, sore throat, fatigue, and loss of taste. These symptoms are most likely caused by COVID-19 or influenza?
Answer: A. COVID-19. Cough, sore throat, and fatigue are symptoms that can be caused by either COVID-19 or flu, however, patients infected with COVID-19 are more likely to present with change in or loss of taste or smell.
Question 2. True or false? COVID-19 and flu viruses spread in similar ways, but transmission via “superspreading” events has been observed more frequently with COVID-19 during the pandemic.
Answer: A. True. Both COVID-19 and flu are transmitted from person-to-person mainly by respiratory droplets made when infected persons cough, sneeze, or talk. Compared to flu, however, transmission of COVID-19 has been more frequently associated with
superspreading events and is more contagious among certain populations and age groups.
Question 3. Complications resulting from both COVID-19 and flu include all the above except which one?
Answer: C. Blood clots. Both COVID-19 and flu can result in pneumonia, respiratory failure, sepsis, and cardiac injury, among others. Blood clots in the veins and arteries of the lungs, heart, legs, or brain as well as multisystem inflammatory syndrome in children are additional complications associated with COVID-19.
Question 4. If an antigen test for COVID-19 is negative, the decision to follow up with a molecular test should consider which of the above?
Answer: F: All of the above. Length of illness (A) is important because after 5 days of symptoms, low antigen levels might lead to a false negative. Even if the antigen test is negative, the patient could have symptoms (B) consistent with SARS-CoV-2 infection and so would need follow-up testing. Type of employment (C) is an essential consideration as frontline workers or those who have regular contact with them might warrant confirmatory testing.
Question 5. For diagnosing influenza, which one of the above characteristics is not shared by rapid molecular assays and rapid influenza diagnostic tests (RIDT)?
Answer: C. High specificity and sensitivity (both >95%). Both rapid molecular assays (eg, PCR) and RIDT are CLIA-waived (A), have specificity of >95% (B), and can produce results in between 15-30 mins (D) (rapid molecular assays, 15-30 mins; RIDT 10-15 mins). However, while RIDT have specificity of between 98%-100%, (depending on virus type) their sensitivity is very low (0%-33%) compared to rapid molecular assays.
Question 6. True or false? For both COVID-19 and flu, ≥1 days can pass between a patient becoming infected and displaying symptoms, but COVID-19 symptoms appear quicker vs flu symptoms.
Answer: B. False. For both COVID-19 and flu, patients may develop symptoms ≥1 days after infection. However, flu symptoms can develop 1-4 days after infection and COVID-19 symptoms typically appear 5 days after infection but can appear as early as 2 days after infection or as late as 14 days after infection.
Question 7. Compared to COVID-19, the risk of complications for flu are higher among which of the above groups?
Answer: D. Children. Older adults, people with certain underlying medical conditions, and pregnant people are all at highest risk for severe illness and complications from COVID-19 and flu. The risk of complications for healthy children is higher for flu vs COVID-19, but infants and children with underlying medical conditions are at increased risk for both flu and COVID-19.