Difference between COVID-19, Flu and Cold

What is the difference between covid-19, the flu and the common cold?

What is the virus?


SARS-CoV-2 is a new coronavirus that emerged in late 2019 and causes the respiratory illness called COVID-19. Many people who contract COVID-19 have mild symptoms while others can become severely ill. While COVID-19 is of concern, it is important to remember that most people displaying symptoms such as fever, cough, sore throat or tiredness are likely suffering from the flu or other respiratory illnesses (CDC, 2020b).


Influenza or ‘the flu’ is a highly contagious respiratory illness. Although you can catch the flu at any time of the year, it is most prevalent during the colder months of April to October in Australia and typically peaks in August.


The cold (also referred to as the common cold) is also a respiratory infection caused by viruses (most commonly Rhinovirus) and affects the upper respiratory tract. According to the American Lung Association, more than 200 different viruses can cause the common cold.

How does the novel coronavirus, flu, and the cold spread?

COVID-19, flu and the cold are transmitted via respiratory droplets are produced when a person exhales, coughs, or sneezes. If you inhale or come into close contact these droplets, you can contract the virus. Additionally, respiratory droplets containing either the cold, flu or new coronavirus can land on objects or surfaces. Touching a contaminated object or surface, and then touching your face, mouth, or eyes may also lead to an infection.


A study by Doremalen et al. (2020) on SARS-CoV-2, the novel coronavirus, showed that viable virus could be found:

  1. up to 3 days on plastic and stainless steel
  2. up to 24 hours on cardboard
  3. up to 4 hours on copper


A study found that viable influenza virus could be detected on plastic and stainless steel surfaces for 24 to 48 hours. The virus was less stable on surfaces such as paper, cloth, and tissue, remaining viable between 8 and 12 hours (Bean et al., 1982).


Cold viruses can only multiply when they are inside living cells (Gwaltney, 1997). When on an environmental surface, cold viruses cannot multiply. However, they are still infectious if they are transported from an environmental site into the nose. Cold viruses may remain infectious for several hours, depending on where they fall. Viruses generally remain active longer on stainless steel, plastic and similar hard surfaces than on fabric and other soft surfaces (Mayo Clinic, 2020). Other factors such as the amount of virus deposited on the surface, the temperature of its surroundings and humidity of the environment also determine how long cold viruses stay infectious on the surface (Mayo Clinic, 2020)

Incubation Period

This refers to the time between the initial infection and the onset of symptoms.


Ranges between 2 to 14 days. According to the Centers for Disease Control and Prevention (CDC), the median incubation period is estimated to be 4 to 5 days (CDC,2020d)


Ranges between 1 to 4 days with an average of about 2 days. (CDC,2020b)


Comes on gradually over 1 to 3 days. (Healthline, 2019)



Most common symptoms include (CDC, 2020d):

  1. Cough
  2. Fever
  3. Fatigue
  4. Shortness of breath

Less common symptoms that some people may experience include (CDC, 2020d):

  1. Body Aches and Pains
  2. Chills
  3. Diarrhoel
  4. Nausea
  5. Headache
  6. Sore/scratchy throat
  7. Loss of Taste
  8. Loss of Smell

Shortness of breath often occurs 5 to 10 days after the first sign of fever. Severe symptoms of COVID-19 that require immediate medical attention include difficulty breathing, persistent pain or pressure in the chest, confusion or inability to arouse, or bluish lips or face, the latter indicating a shortage of oxygen in the bloodstream (CDC, 2020b). Some people with COVID-19 will be asymptomatic, that is not experiencing any symptoms or may only experience very mild symptoms. Often times, an older person will NOT have a fever. (Department of Health Australia, 2020).


People that have the flu experience some or all of the following symptoms (CDC, 2020d):

  1. Body Aches
  2. Congestion
  3. Cough
  4. Chills
  5. Fatigue
  6. Fever
  7. Headache
  8. Runny Nose
  9. Sore Throat

Less Common Symptoms:

  1. Diarrhoeal
  2. Nausea

Not everybody that has the flu will develop a fever, however, it still must be treated seriously the person will nonetheless be contagious. Even without an elevation in body temperature the flu can progress and become a concern especially for older adults or those with chronic illness and compromised immune systems. The digestive symptoms like vomiting and diarrhea are more common in young children with the flu (CDC, 2020d) While fatigue and body aches are symptoms of both the flu and the novel coronavirus, the flu usually does not cause shortness of breath.


Early symptoms include (Healthline, 2020):

  1. Tickle or Scratchiness in the back of the Throat
  2. Sneezing
  3. Fatigue

Common symptoms consist of:

  1. Congestion
  2. Cough
  3. Fatigue
  4. Headaches
  5. Runny Nose
  6. Sneezing
  7. Sore Throat

Less Common Symptoms include:

  1. Chills
  2. Fever
  3. Severe Headache
  4. Sinus Pain

Generally, a cold and flu will not cause shortness of breath unless it has progressed to pneumonia.



1 in 5 people who contract COVID-19 can become seriously ill and develop difficulty breathing (WHO, 2020). Elderly people and those with underlying medical problems like high blood pressure, heart and lung problems, diabetes, or cancer, are at higher risk of developing a serious illness. However, anyone who catches COVID-19 can become seriously ill (CDC, 2020b).


In some people, symptoms like cough and fatigue may stay for 2 weeks or longer. About 1% of flu cases leads to hospitalisation, and less than 1% of flu cases become fatal (CDC, 2020e).


Mild colds may last only 2 or 3 days while severe colds may last for up to 2 weeks (Lung, 2020)

Contagious Periods


The period that a person with COVID-19 is contagious is still poorly understood. CDC reports that people are most contagious when they show symptoms (CDC, 2020d) While it may be possible to spread COVID-19 before you show symptoms (WHO, 2020), this is not currently believed to be a major factor in its spread (CDC, 2020d). Until researchers understand more about COVID-19, .it is important for all of us to practice social distancing and remain 1.5 metres apart.


A person with the flu is most contagious in the first 3-4 days after the illness begins. Some otherwise healthy adults may spread the virus as early as a day before the onset of symptoms and up to 5 to 7 days after becoming ill (CDC,2020a).


Cold is most contagious at the early onset of symptoms (feeling a bit tired, sneezing, and itchy throats) so it is best to stay home and rest during this time. As a rule, people are most contagious 3 days after initial exposure to the virus (Heath Direct, 2020b).

Vaccines and Medications


There are currently no licensed vaccines available to protect against COVID-19. Additionally, there are no specific medications recommended for treatment of COVID-19


Vaccinations are available for the seasonal flu and are updated every year to target the influenza virus strains predicted to be the most common. Getting a seasonal flu vaccine is an effective way to prevent becoming sick with the flu. However, people can still get the flu after being vaccinated, though symptoms may be milder. There are antiviral medications available for the flu, which treats viruses in the body and inhibit their development. Antibiotics do not treat the flu, they only work on bacteria


There is no vaccine for the common cold mainly because there are more than 200 different strains. People can generally relieve the milder symptoms of a cold with over-the-counter medications. Antibiotics cannot treat a cold as they can only treat illnesses caused by bacteria, not by viruses.

Can a flu shot protect you from COVID-19?

COVID-19 and the flu are caused by completely separate viruses with no current evidence showing the flu vaccine protects against COVID-19. However, it is still important to get vaccinated for the flu this year to help protect yourself, especially if you are in an at-risk group.


Reference List

Bean, B., Moore, B., Sterner, B., Peterson, L., Gerding, D. and Balfour, H., 1982. Survival of Influenza Viruses on Environmental Surfaces. Journal of Infectious Diseases, 146(1), pp.47-51.

Centers for Disease Control and Prevention. 2020a. Key Facts About Influenza (Flu) | CDC. [online] Available at: <https://www.cdc.gov/flu/about/keyfacts.htm> [Accessed 9 May 2020].

Centers for Disease Control and Prevention. 2020b. Coronavirus Disease 2019 (COVID-19). [online] Available at: <https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-guidance-management-patients.html> [Accessed 9 May 2020].

Centers for Disease Control and Prevention. 2020c. Clinical Signs And Symptoms Ofof Influenza | CDC. [online] Available at: <https://www.cdc.gov/flu/professionals/acip/clinical.htm> [Accessed 12 May 2020].

Centers for Disease Control and Prevention. 2020d. Coronavirus Disease 2019 (COVID-19) – Symptoms. [online] Available at: <https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html> [Accessed 9 May 2020].

Centers for Disease Control and Prevention. 2020e. Preliminary In-Season 2019-2020 Flu Burden Estimates. [online] Available at: <https://www.cdc.gov/flu/about/burden/preliminary-in-season-estimates.htm> [Accessed 10 May 2020].

Gwaltney, J.M.Jr. 1997. Rhinoviruses. In Viral Infection of Humans: Epidemiology and Control, 4th ed. A.S. Evans, and R.A. Kaslow, editors. Plenum Press, New York. 815-838.

Healthline. 2020. Incubation Period Forfor Cold, Early Symptoms, And When It’sIt is Contagious. [online] Available at: <https://www.healthline.com/health/incubation-period-for-cold#early-treatments> [Accessed 12 May 2020].

Healthdirect, 2020a. Colds Andand Flu. [online] Available at: <https://www.healthdirect.gov.au/colds-and-flu> [Accessed 12 May 2020].

Healthdirect, 2020b. Colds. [online] Available at: <https://www.healthdirect.gov.au/coldsu> [Accessed 12 May 2020].

Lung.org. 2020. Facts About The Common Cold. [online] Available at: <https://www.lung.org/lung-health-and-diseases/lung-disease-lookup/influenza/facts-about-the-common-cold.html> [Accessed 12 May 2020].

Mayo Clinic 2020. Cold and Flu Viruses: How long can they live outside the body? [online] Available at :http://www.mayoclinic.org/diseases-conditions/flu/expert-answers/infectious-disease/faq-20057907 [Accessed 24 May 2020].

WHO, 2020. Q&A Onon Coronaviruses (COVID-19). [online] Available at: <https://www.who.int/emergencies/diseases/novel-coronavirus-2019/question-and-answers-hub/q-a-detail/q-a-coronaviruses> [Accessed 9 May 2020].

van Doremalen, N., Bushmaker, T., Morris, D., Holbrook, M., Gamble, A., Williamson, B., Tamin, A., Harcourt, J., Thornburg, N., Gerber, S., Lloyd-Smith, J., de Wit, E. and Munster, V., 2020. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. New England Journal of Medicine, 382(16), pp.1564-1567.