Influenza Virus

Symptoms and complications of Influenza

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Influenza vs common cold

Influenza and cold have similar influenza-like symptoms but in general influenza is worse than the common cold, and symptoms such as fever, body aches, extreme tiredness, and dry cough are more common and intense with more rapid onset. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems such as pneumonia, bacterial infections, or hospitalizations.

Is it a Cold or Flu?

Signs & symptoms Cold Flu
Symptom onset Gradual Abrupt
Fever Rare Usual
Aches Slight Usual
Chills Uncommon Fairly common
Fatigue, weakness Sometimes Usual
Sneezing Common Sometimes
Chest discomfort, cough Mild to moderate Common
Stuffy nose Common Sometimes
Sore throat Common Sometimes
Headache Rare Common

What is the difference between Influenza (Flu) and COVID-19?

Influenza (Flu) and COVID-19 are both contagious respiratory illnesses, but they are caused by different viruses. COVID-19 is caused by infection with a new coronavirus (called SARS-CoV-2) and flu is caused by infection with influenza viruses. Because some of the symptoms of flu and COVID-19 are similar, it may be hard to tell the difference between them based on symptoms alone, and testing may be needed to help confirm a diagnosis. Flu and COVID-19 share many characteristics, but there are some key differences between the two.1

It is possible have flu, as well as other respiratory illnesses, and COVID-19 at the same time. Health experts are still studying how common this can be.2

In the late 2019, a novel Coronavirus, SARS-CoV-2, emerged as a cause of severe respiratory illness 3. In March 2020, the World Health Organization (WHO) declared coronavirus disease 2019 (COVID-19) a global pandemic.3 The common signs and symptoms of COVID-19 (e.g., fever, cough, and dyspnea)3 can also occur with influenza illness. As of August 2020, SARS-CoV-2 continues to circulate and cause severe illness in the United States and worldwide. The extent to which SARS-CoV-2 will circulate over the course of the 2020–21 influenza season is unknown. However, during the continued or recurrent circulation of SARS-CoV-2 concurrently with influenza viruses during the upcoming fall and winter, influenza vaccination of persons aged ≥6 months can reduce prevalence of illness caused by influenza, and can also reduce symptoms that might be confused with those of COVID-19. Prevention of and reduction in the severity of influenza illness and reduction of outpatient illnesses, hospitalizations, and intensive care unit admissions through influenza vaccination also could alleviate stress on the U.S. health care system.

Influenza versus COVID-19

Flu Covid-19
R0 1.3 2.4 - 3.5
CFR 0.05 - 0,1% 3.4% (higher in older age group and people with comorbidities)
Incubation time 1 - 4 days 2 - 14 days
Hospitalization rate 2% 19 - 20%
Annual infected (global) 1 billion N/A (ongoing)

WHY vaccinate against flu during the COVID-19 pandemic?

Prevention of influenza

  • Respiratory viral infections can claim lives of thousands of people
  • We should prevent what can be prevented by optimally using influenza vaccines

Reduce the burden on healthcare systems

  • Reduce the number of patients seeking health care
  • Free doctors and health care facilities for people infected with SARS-CoV-2 virus to receive immediate care.

Reduce the risk of catching influenza

  • Reduce the risk of contaminating family members and others who may be at higher risk of serious complications from influenza and/or COVID-19.
  • Help reduce the risk of contracting SARS-CoV-2 from going into the healthcare system due to influenza infection and being exposed to people potentially contaminated with SARSCoV-2.