The Flu: Causes

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What causes the flu?

The flu is an upper respiratory tract infections (URTIs) caused by the influenza virus,2,3 typically types A and B, which cause seasonal epidemics every year.

Type C is detected less often and usually causes mild symptoms.1

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Transmission of the Flu

Influenza virus particles are spread from person to person within tiny droplets formed when coughing, sneezing, or talking.4-6

These infected droplets are then transmitted to another person who either:5,6

  • Breathes in the airborne droplets
  • Comes into close contact with an infected person
  • Touches a contaminated surface and then touches their mouth, nose, or eyes

Anyone can get the flu, but it can be more serious in certain groups of people:1

  • People aged 65 and over
  • Pregnant women
  • People with serious medical conditions such as diabetes, HIV, chronic respiratory, cardiac or cancer conditions
  • Babies/young children

  • The Contagious Period

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    How long is flu contagious?

    An infected person may be able to spread the flu before even becoming symptomatic.4

    The highest point of contagiousness is within the first 3-4 days after the illness begins, but most adults may be considered infective 1 day prior to demonstrating symptoms.4

    Healthy adults can be capable of spreading the virus for up to 7 days into their flu episode, but children and immunocompromised patients may be contagious for a longer period.4

  • Reducing Risk

    Reducing the risk of contracting the flu

    Due to the constantly evolving nature of influenza viruses, the composition of the flu vaccine is updated every year as necessary.7

    In addition to this, patients can be counselled to reduce their risk of infection and the risk of spreading it to others.

    Young woman with curly black hair catches her sneeze in a tissue while sitting on her sofa working from home on her laptop

    1. Use a tissue to cover coughs and sneezes

    Cough or sneeze into a tissue, and then immediately dispose of it.8

    Woman with manicured nails washes her hands in a sink

    2. Wash your hands regularly

    Wash your hands regularly and thoroughly with soap and water for at least 20 seconds. If soap and water is not available, use an alcohol-based hand sanitizer.8

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    3. Avoid touching your face

    The flu virus can be caught through the process of “self-inoculation”, which refers to a person touching an infected surface and then transferring virus particles to themselves by touching their eyes, nose, or mouth.5,8

    Where possible, avoid touching your face.

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    4. Routine cleaning

    The flu virus can “live” on some surfaces for up to 48 hours. Routine cleaning of surfaces can help to reduce the spread of flu.9

    Young man sits on a grey sofa with a striped blanket draped over his shoulders holding a mug of coffee and a tissue

    5. Self isolation

    Avoiding close contact with people that are ill and early self-isolation of those feeling unwell is recommended.

    For those who have been ill with flu symptoms, remaining isolated for at least 24 hours after their fever is gone is also advised.10

Young woman wearing a brown knitted hat and gloves blows her nose into a tissue while standing under an umbrella

How does climate change affect the spread of influenza?

There is a growing amount of work investigating the links between climate change and respiratory diseases such as influenza, helping to ensure medical and public health experts are prepared for any future challenges.11

Viral respiratory tract infections are the most common human illness, with approximately 17bn incidences recorded in 2019.11

Studies have shown what most health professionals may understand well: with lower temperatures, the likelihood of influenza rises.11,12 A similar association was seen with humidity, where a lower absolute humidity also led to a rise in influenza.12

Warmer winters were also found to be linked to more severe epidemics of influenza A and B the following year.11 And in tropical climates, increased temperatures were associated with higher rates of respiratory infections.11

Multiple studies have also shown that when extreme precipitation (snow, rain, hail) events occur, influenza cases often rise shortly afterwards.13-18

Being aware of the climate or weather changes that are occurring, as well as their severity, could help you plan for a potential rise in patients seeking flu medications.

Theraflu – the Power to Feel Better

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