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 A 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 100.4°F, 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 CDC reports that each year since 2010, there have been 9.2 million to 36 million cases of influenza in the United States. The number of annual outpatient visits associated with influenza has been estimated at 31 million.7
  • Annually, influenza is responsible for 140,000 to 710,000 hospitalizations and up to 56,000 deaths.8

The resultant economic burden is huge. In 2003 it was estimated that:

  • The 3.1 million hospitalized days and 31.4 million outpatient visits were responsible for direct medical costs of $10.4 billion.
  • Lost earnings due to illness and loss of life totaled $16.3 billion.
  • The total burden annually amounted to $87.1 billion, an amount that can lead to a reduction in the rate of economic growth.9

Several factors are at play when determining the severity of a seasonal influenza outbreak in the United States. 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 (and in many cases free) every year, many people choose not to get vaccinated, which can increase the likelihood of both catching influenza and exposing others to the virus. The CDC estimates that between 2015 and 2016, five million flu-related illnesses and two and a half million medical office visits were prevented due to vaccinations.10

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.11 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.12

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.13

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.14, 15 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 Prevention

According to the CDC, the best way to prevent the spread of the influenza virus is to get vaccinated.16 This is by far the most underutilized method of prevention, given the effectiveness and low cost of the flu vaccine. The CDC also recommends six steps related to general hygiene that can further prevent the spread of the virus:

  1. Avoid touching your eyes, nose and mouth: This is especially important after touching common environmental surfaces during flu season that may be contaminated with the flu virus. Since germs are typically spread by touching contaminated surfaces and then touching the nose, mouth or eyes, hands should be washed after touching potentially contaminated surfaces. Additionally, if you have influenza, you should avoid touching environmental surfaces after you have touched your nose, mouth or eyes.
  2. Wash your hands: Washing hands is crucial during flu season to prevent the spread or acquisition of influenza. The virus can easily be transferred from doorknobs, phones and other surfaces to hands and then to the nose or mouth. Making a habit out of regularly washing your hands with soap and water decreases the likelihood of acquiring influenza from your surroundings.
  3. Stay home if you are sick: In order to give yourself adequate time to recover, it is important to stay home and rest if you have the flu. During this period it is important to hydrate, sleep and allow the body time to fight off the infection. Staying home will also help prevent the possibility of spreading influenza to others.
  4. Avoid close contact: Since influenza is commonly spread via droplets that travel through the air after a sick person sneezes, coughs or even talks, it is important to avoid close contact with people who have the flu and are likely to be contagious.
  5. Cover your mouth and nose: If you are sick, sneezing or coughing into a tissue or your arm will help prevent virus particles from traveling through the air and infecting other people or contaminating surfaces.
  6. Practice other healthy habits: Help your immune system avoid catching the flu by practicing simple healthy habits. Get plenty of sleep, exercise regularly, eat healthy foods and stay hydrated.

Cleaning and Disinfecting Environmental Surfaces

Regular cleaning and disinfection of environmental surfaces in the household using a disinfectant that is approved by the Environmental Protection Agency (EPA) 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 EPA-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.

6. Help Prevent the Spread of Influenza with CloroxPro Products

A number of Clorox products are EPA 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 EPA reg. no. Active ingredient Contact/wet time:  Contact/wet time: 
Influenza A Influenza B
Clorox Healthcare® Bleach Germicidal Wipes                  67619-12                  Sodium hypochlorite 1 min 1 min
Clorox Healthcare® Bleach Germicidal Cleaner Spray 56392-7 Sodium hypochlorite 1 min 1 min
Dispatch® Hospital Cleaner Disinfectant Towels with Bleach 56392-8 Sodium hypochlorite 1 min 1 min
Clorox Healthcare® Fuzion Disinfectant Cleaner 67619-30                  Sodium hypochlorite 1 min 1 min
Clorox® Clean-Up® Disinfectant Cleaner with Bleach1 67619-17                  Sodium hypochlorite 30 sec Not tested
Clorox® Germicidal Bleach 67619-32                  Sodium hypochlorite 5 min 5 min
Clorox® Tilex Disinfects Instant Mold and Mildew Remover 5813-24-67619 Sodium hypochlorite 5 min Not tested
Clorox Healthcare® Hydrogen Peroxide Cleaner Disinfectant Wipes 67619-25                  Hydrogen peroxide 30 sec 30 sec
Clorox Healthcare® Hydrogen Peroxide Cleaner Disinfectant 67619-24                  Hydrogen peroxide 30 sec 30 sec
Clorox Healthcare® Multi-Surface Quat Alcohol Cleaner Disinfectant Wipes 70144-2-67619 Quaternary ammonium chloride 2 min Not tested
Clorox® Broad Spectrum Quaternary Disinfectant Cleaner 67619-20                  Quaternary ammonium chloride 2 min Not tested
Clorox Healthcare® Disinfecting Wipes 67619-9 Quaternary ammonium chloride 4 min Not tested
Clorox® Pro Quaternary All-Purpose Disinfectant Cleaner 1839-166-67619 Quaternary ammonium chloride 10 min Not tested
Clorox® Total 360® Disinfectant Cleaner4 1839-220-67619 Quaternary ammonium chloride 30 sec Not tested
Clorox® Disinfecting Spray 67619-21                  Quaternary ammonium chloride-alcohol 30 sec 30 sec
Clorox Healthcare® EZ-KILL® Quat Alcohol Cleaner Disinfectant Wipes 59894-10-67454                  Quaternary ammonium chloride-alcohol 2 min Not tested
Pine-Sol® Multi-Surface Cleaner 5813-101-67619 Glycolic acid 10 min Not tested
Clorox Healthcare® Citrace® Hospital Disinfectant & Deodorizer 67619-29                  Alcohol 5 min Not tested
Clorox® 4 in One Disinfectant & Sanitizer 67619-29                  Alcohol 5 min Not tested


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3. Mayo Clinic. Influenza (Flu). Accessed December 12, 2017.
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10. Centers for Disease Control and Prevention. CDC Newsroom: Flu Vaccine Coverage Remains Low this Year. Accessed December 12, 2017.
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15. 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.
16. Centers for Disease Control and Prevention. Seasonal Influenza (Flu): Preventing the Flu: Good Health Habits Can Help Stop Germs. Accessed December 12, 2017.