Colds and flu

Updated 25 March 2019

Flu risk factors

Certain groups of people are more susceptible to getting the flu, while others risk developing complications.

In the community, preschool and school children are at highest risk of contracting the flu as they have limited pre-existing immunity. Infection risk is also high among residents of old-age homes and members of closed communities, such as long-term care facilities, military bases and university campuses.

Most people experience the flu as a mild illness – no medical care or specific drugs are required, and you should recover within two weeks.

However, certain age groups and people with underlying medical conditions are more susceptible to developing complications from the flu requiring hospitalisation. Flu can also lead to worsening of pre-existing medical conditions – for example, it can cause asthma attacks in those with underlying asthma.

People at highest risk of developing flu complications are:

  • Children younger than five years, especially those younger than two years of age
  • Adults 65 years and older
  • Pregnant women and new mothers (there’s an increased risk during the first two weeks after delivery)
  • Residents of nursing homes and long-term care facilities

Certain underlying medical conditions can also place you at higher risk for flu complications. These conditions include:

  • Lung conditions, e.g. asthma, emphysema and cystic fibrosis.
  • Neurological and neurodevelopmental conditions, e.g. intellectual disability or any condition that compromises an individual’s ability to breathe, cough or clear mucus optimally.
  • Heart diseases, e.g. congestive heart failure, coronary disease and congenital heart disease.
  • Blood disorders, e.g. sickle cell disease.
  • Diabetes
  • Kidney disorders
  • Liver disease
  • Immune deficiencies due to diseases such as HIV and cancer, certain medications (e.g. long-term steroids), or organ transplantation.
  • Extreme obesity (BMI over 40)

Reviewed by Cape Town-based general practitioner, Dr Dalia Hack. March 2019.

Read more:

- Who gets the flu?

- What causes the flu?


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Dr Heidi van Deventer completed her MBChB (Bachelor of Medicine and Bachelor of Surgery) degree in 2004 at the University of Stellenbosch.
She has additional training in ACLS (Advanced Cardiac Life Support) and PALS (Paediatric Advanced Life Support) as well as biostatistics and epidemiology.

Dr Van Deventer is currently working as a researcher at the Desmond Tutu Tuberculosis Centre at the University of Stellenbosch.

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