Preventing the Spread of Influenza

1. Basic Facts About Influenza

What Is Influenza?

Influenza, commonly referred to as the flu, is a contagious viral infection caused by the influenza A or B viruses. The illness is associated with the upper respiratory system, and symptoms range from mild to severe. It is considered to be most dangerous among the elderly, young children and others with inhibited or weak immune systems due to the significant toll infection can take on the body. Outbreaks of influenza are considered to be seasonal, with the highest number of cases occurring during the winter. Both the influenza A and B viruses typically cause the annual epidemics experienced every winter in the United States. The influenza A virus can be divided by subtype depending on the arrangement of two proteins on the surface of the virus: hemagglutinin (H) and neuraminidase (N).1 During the past 40 years, the most common influenza viruses circulating globally are influenza A (H1N1), influenza A (H3N2) and influenza B.

Influenza Symptoms

Unlike other illnesses associated with symptoms that occur gradually, symptoms attributed to the flu often begin simultaneously and suddenly for individuals who have recently been infected.2 The influenza virus begins by infecting the nose, throat and sometimes the lungs. It moves to other parts of the body, causing muscle soreness, fatigue and headaches. Fever is common, with temperatures often over 38°C, although this does not occur in all cases.3 Other common influenza symptoms include:

  • Stuffy or runny nose
  • Severe fatigue or inhibited levels of energy
  • Headaches
  • Chills or sweats
  • Muscle aches or body soreness
  • Coughing, sore throat, raspy voice

The influenza virus should not be confused with the illness commonly referred to as the stomach flu, which is usually caused by norovirus. The stomach flu results in symptoms such as vomiting or diarrhea which are not commonly associated with an influenza virus.

How Long Does the Flu Last?

In normally healthy people, symptoms often last between five and seven days.4 The severity of these symptoms can take a dramatic toll on one’s ability to do work or everyday tasks, often requiring infected people to take time off of work to rest and recover. Healthy adults are usually able to fully recover from influenza symptoms in about a week. Symptoms may be more severe in young children, those over 65, pregnant women and those with chronic illnesses or compromised immune systems (such as diabetes, HIV and heart disease) and may be associated with complications such as pneumonia and longer recovery times.

lnfluenza Incubation Period

The incubation period for an illness is the time that elapses between first exposure and the appearance of symptoms. While the incubation period for influenza varies, one to four days is typical, with most adults averaging two days.5 During this time people who have been exposed and infected with the virus can still pass it on to others before experiencing symptoms themselves.

Who ls at Risk?

Like other highly contagious illnesses, influenza is a threat to anyone who is regularly exposed to other people in the workplace, healthcare facilities, schools and colleges, malls, theaters, or on public transport systems. Although the elderly, young children and people with weakened immune systems are most at risk for severe or deadly symptoms, healthy adults can miss days or weeks of work when infected. Due to the seriousness and potential severity of influenza’s symptoms, everyone should take extra precautions during the flu season to prevent the spread of the virus.

How ls lnfluenza Diagnosed?

Diagnostic tests are available for the influenza virus. Methods of testing include viral culture, rapid antigen testing, reverse transcription polymerase chain reaction and rapid molecular assays.6 Diagnostic tests are most valuable for determining whether influenza is the cause of an illness outbreak in closed settings such as schools, hospitals, cruise ships, long-term care facilities or other institutional facilities. However, diagnostic tests are not always performed on an individual basis when influenza is suspected, given that the symptoms are common to other illnesses and the treatment is similar for multiple strain types. When a test is performed, the doctor will most likely use a swab to take a sample from the back of the nose or throat to test for the presence of influenza A antigens.4

Influenza Treatment

For many healthy adults experiencing symptoms commonly associated with the flu, doctors will simply recommend bed rest and hydration. During this period, it is recommended that individuals limit or prevent exposing themselves to others to decrease the likelihood of transmission. Rest is also crucial during this period to allow the immune system to fight the influenza virus.

When complications associated with influenza are a concern, antiviral medication may be prescribed. These can shorten the illness by a day or two, and can help reduce the risk of the development of other potentially dangerous complications. The most common medications prescribed include oseltamivir (Tamiflu®) and zanamivir (Relenza®).4

2. The Burden of Influenza

There are significant medical burdens associated with influenza:

  • The Public Health Agency of Canada estimates that in a given year, there is an average of 12,200 hospitalizations related to influenza in Canada.7
  • Approximately 3,500 Canadians die of the flu each year, making it one of the 10 leading
    causes of death in Canada.7

The resultant economic burden is huge. It is estimated that:

  • 1.5 million workdays are lost each year due to the flu virus.8
  • $1 billion is cost to the Canadian system due to the flu virus (in healthcare and lost productivity).8
  • Canadians spend each year $300 million on cold and flu virus treatments, making them the second most commonly used medications in Canada.9

Several factors are at play when determining the severity of a seasonal influenza outbreak. These include the effectiveness of the flu vaccine against the circulating influenza strains in a given season, the number of people who are vaccinated, and the timing of the outbreak. Although influenza vaccines are always readily available every year, many people choose not to get vaccinated, which can increase the likelihood of both catching influenza and exposing others to the virus. It’s in everyone’s best interest to be proactive when it comes to the cold and flu.

3. How Influenza Spreads

Person-to-Person Transmission

The most common person-to-person mode of transmission is via large respiratory droplets. These are expelled when infected people sneeze, talk or cough, and are inhaled by people nearby. The large droplets do not remain suspended in the air for very long, and transmission normally requires people to be in close contact — within three feet or less.10 Airborne transmission through smaller droplet aerosols that can be exhaled or that result from evaporation of water from larger droplets may play a role in transmission; these droplets can exist in the air for longer and may also be able to infect people.11

Person-to-person transmission may also occur after a sick person who has contaminated hands from sneezing or coughing into them touches another person, even though the virus may only survive on hands for a few minutes.12

The ease of transmission makes influenza a serious problem in areas where large numbers of people congregate, such as workplaces, schools, colleges, healthcare facilities and public events. Many people can spread the influenza virus without knowing it. Healthy adults are able to infect others with the flu beginning one day before they experience symptoms, and can transmit the virus for up to seven days after experiencing sickness. Children and others with weaker immune systems can transmit the virus for even longer than seven days.

The Role of Surfaces in the Spread of Influenza

Although influenza is more commonly spread through droplets that are inhaled by otherwise healthy people, hard and soft surfaces also play a role. Studies report that both influenza A and B viruses can live on stainless steel, plastic and other nonporous hard surfaces for up to 48 hours.13, 14 On soft surfaces such as tissues, paper and cloth, the virus has been shown to survive for up to 12 hours.15 These surfaces may become contaminated with virus particles from infected droplets in the air. Touching these surfaces can contaminate hands, which can then transmit the virus to the mouth, nose and upper respiratory tract. Transmission from surfaces can pose an issue to people who work in environments that require them to share surfaces with many other people on a daily basis, or to people using public transport systems.

4. Preventing the Spread of Influenza

Six Steps for Prevention15:

  1. Encourage vaccinations
    Vaccination is the best protection
    against contracting the flu.
  2. Practice proper hand hygiene. Wash hands carefully and frequently with soap and water. Alcohol-based hand sanitizers containing at least 62% alcohol are also effective.
  3. Ensure frequent cleaning and disinfecting of commonly touched surfaces.
  4. Use Health Canada registered disinfectants with an influenza claim.
  5.  Cough or sneeze into elbows. Avoid coughing or sneezing into hands, which are more likely to spread bacteria and the flu virus through touch.
  6. Stay home. Encourage those who are sick to stay home and limit contact with others.

Cleaning and Disinfecting Environmental Surfaces

Regular cleaning and disinfection of environmental surfaces in the household using a disinfectant that is approved by the Health Canada to inactivate influenza viruses also helps prevent the spread of influenza. A wide range of disinfectants that contain a number of active ingredients — quaternary ammonium chlorides, sodium hypochlorite (bleach) and hydrogen peroxide — are Health Canada-approved to inactivate influenza A and B viruses.

Thorough cleaning and disinfection is also important in institutional settings such as schools, colleges, healthcare facilities and public transport systems, especially in winter months when influenza risk is increased. When using a disinfectant, always follow the product label’s directions for use and allow the disinfectant to stay wet on the surface for the indicated contact time to make sure the virus is inactivated.

5. Help Prevent the Spread of Influenza with CloroxPro Products

A number of CloroxPro products are Health Canada approved against influenza A and B viruses. Use these in your daily cleaning and disinfection to prevent the transmission of influenza and reduce the burden of infection in your household or facility. The contact time, or wet time, is the time that the surface must remain visibly wet for the disinfectant to be effective against the specific influenza virus.


Product DIN No Active ingredient Contact/wet time:  Contact/wet time: 
Influenza A Influenza B
Clorox Healthcare® Bleach Germicidal Wipes 02465671 Sodium hypochlorite 1 min 1 min
Clorox Healthcare® Bleach Germicidal Cleaner Spray 02469278 Sodium hypochlorite 1 min 1 min
Clorox Healthcare® Fuzion Disinfectant Cleaner 02459744 Sodium hypochlorite 1 min 1 min
Clorox® Clean-Up® Disinfectant Cleaner with Bleach 02494019 Sodium hypochlorite 30 sec Not tested
Clorox® Germicidal Bleach 02459108 Sodium hypochlorite 5 min 5 min
Clorox Healthcare® Hydrogen Peroxide Cleaner Disinfectant Wipes 02406225 Hydrogen peroxide 30 sec 30 sec
Clorox Healthcare® Hydrogen Peroxide Cleaner Disinfectant 02403528 Hydrogen peroxide 30 sec 30 sec
Clorox® Disinfecting Wipes 02492636 Quaternary ammonium chloride 4 min Not tested
Clorox® Total 360® Disinfectant Cleaner 02460769 Quaternary ammonium chloride 30 sec Not tested
Pine-Sol® All-Purpose Cleaner 02407132 Glycolic acid 10 min Not tested


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2. Centers for Disease Control and Prevention. Seasonal Influenza (Flu): Key Facts about Influenza (Flu). Accessed December 12, 2017.
3. Mayo Clinic. Influenza (Flu). Accessed December 12, 2017.
4. Godman H. How Long Does the Influenza Last? Harvard Health Publishing. Accessed December 12, 2017.
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6. Seasonal Influenza (Flu): Influenza Signs and Symptoms and the Role of Laboratory Diagnostics. Centers for Disease Control and Prevention website. Accessed December 12, 2017.
7. Public Health Agency of Canada. Statement on Seasonal Influenza Vaccine for 2014-2015. Accessed August 17, 2020.
8. Canadian Healthcare Influenza Immunization Network. Influenza Facts. Accessed August 17, 2020.
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14. Bean B, Moore BM, Sterner B, Peterson LR, Gerding DN, Balfour HH Jr. Survival of Influenza Viruses on Environmental Surfaces. J Infect Dis. 1982;146(1): 47-51.
15. Public Health Agency of Canada. Flu (influenza): Prevention and risks. Accessed November 8, 2020.