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ARE COUGHS CONTAGIOUS?

Can you catch a cough?

A cough can be caused by many different things, including:1,2

  • common cold (usually caused by a virus)2    
  • influenza or flu (caused by a virus)3    
  • upper airways cough syndrome (formally known as postnasal drip syndrome)1   
  • asthma1    
  • gastro oesophageal reflux disease (GORD)1   
  • smoking4     
  • medication (e.g. a type of blood pressure medication called Ace inhibitors can cause chronic coughing)1
  • bronchitis.1

Some of these causes of cough, like flu3 and the common cold,2 may be contagious (i.e. they can spread from one person to another) whilst other causes, like cigarette smoking or taking regular blood pressure medication, are not. It follows that some coughs may be contagious but others will not be, depending on the cause of the cough.

However, acute cough caused by viral respiratory tract infections is probably the most common illness in humans.5 Infectious respiratory diseases (such as flu or the common cold) can be transmitted to a non-infected person when the infected person coughs and expels droplets (called aerosols) that contain the infectious agent into the environment around them.6

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How contagious is infection-related coughing?

Some pathogens infect us more readily than other pathogens do6 and some people (e.g. children younger than six, smokers and people with a weakened immune system) are more prone to catching infectious conditions than others are.7

Scientists are still learning about how contagious the different cough-causing infections are.8 The type of cough, and the kind of mucus it produces, may have something to do with how contagious it is.9

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What can you do to prevent cough contagion?

Scientists fear that there’s little you can do to protect yourself from aerosol particles that can carry an infectious agent. Traditional cough etiquette doesn’t always work: covering your mouth and not coughing directly at people will not necessarily spare them exposure to your bug, particularly if it is a very contagious bug.6 This is why unvaccinated adolescents often catch whooping cough from their friends.10

Better ventilation doesn’t work either.11 Disinfecting hospital air might work,12 and so might the practice of isolated rooms in the hospital setting.13 It seems that particles and bio-aerosols find their way around hospitals and homes almost no matter what.14 Experts are starting to wonder if much of our understanding of cough contagion and prevention is, in fact, an oversimplification.15

The study of environment and infection continues,16 but in the meantime the following tips could help prevent the spread of a contagious cough:

  • The most important way to prevent transfer of respiratory infections is to wash your hands thoroughly and regularly, either with soap or an alcohol-based rub, particularly when in contact with people who are coughing or sick.2,17    
  • Dispose of tissues that have nasal secretions in them and avoid contact with phlegm that people cough up.2    
  • Cover your mouth and turn away from other people when you cough. Although it won’t stop all the infected aerosol droplets spreading, it is likely that at least some will be stopped this way.6     
  • If you are sick, stay away from work or school so you don’t pass on the bug.2
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References

  1. BMJ Best Practice. Chronic cough. Last updated: 21 Jun 2018. Available at: https://bestpractice.bmj.com/. Last accessed May 2019.
  2. BMJ Best Practice. Common cold. Last updated: 19 Oct 2018. Available at: https://bestpractice.bmj.com/. Last accessed May 2019.
  3. BMJ Best Practice. Influenza infection. Last updated: 05 Mar 2019. Available at: https://bestpractice.bmj.com/. Last accessed May 2019.
  4. Verywell Health. Overview of the smoker’s cough. Last updated: 20 Mar 2019. Available at: https://www.verywellhealth.com/smokers-cough-symptoms-and-causes-2248937. Last accessed May 2019.
  5. Morice AH. Comprehensive evidence-based review on European antitussives. BMJ Open Resp Res 2016; 3e 000137.
  6. Zayas G et al. Effectiveness of cough etiquette maneuvers in disrupting the chain of transmission of infectious respiratory diseases. BMC Public Health 2013; 13:811.
  7. Mayo Clinic. Common cold. Last updated: 20 Apr 2019. Available at: https://www.mayoclinic.org/diseases-conditions/common-cold/symptoms-causes/syc-20351605. Last accessed May 2019.
  8. Funk S. Modelling the influence of human behaviour on the spread of infectious diseases: a review. J R Soc Interface 2010; 7:1247-1256.
  9. Turner RD. Cough and the transmission of tuberculosis. J Infect Dis 2015; 211:1367- 1372.
  10. Schellekens J. Pertussis sources of infection and routes of transmission in the vaccination era. Pediatr Infect Dis J 2005; 24:S19-24.
  11. Thatiparti DS. Computational fluid dynamics study on the influence of an alternate ventilation configuration on the possible flow path of infectious cough aerosols in a mock airborne infection isolation room. Sci Technol Built Environ 2016; 23:355-366.
  12. Guimera D. Effectiveness of a shielded ultraviolet C air disinfection system in an inpatient pharmacy of a tertiary care children’s hospital.Am J Infect Control 2018; 46:223-225.
  13. Miller SL. Implementing a negative-pressure isolation ward for a surge in airborne infectious patients. Am J Infect Control 2017; 45(6):652-659.
  14. He C. Particle and bioaerosol characteristics in a paediatric intensive care unit. Environ Int 2017; 107:89-99.
  15. MacIntyre CR. The efficacy of medical masks and respirators against respiratory infection in healthcare workers. Influenza Other Respir Viruses 2017; 11:511-517.
  16. Walser SM. Environmental health relevance of airborne microorganisms in ambient and indoor air. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2017; 60(6):618-624.
  17. BMJ Best Practice. Acute sinusitus. Last updated: 01 Mar 2019. Available at: https://bestpractice.bmj.com/. Last accessed May 2019.