Common questions about influenza (the flu)

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Last updated: October 2023

Find answers to common questions about influenza. Learn how it spreads, how long after exposure symptoms take to appear and what symptoms to look for. Find out what you can do to prevent influenza, including vaccination and handwashing. You can also find more resources about influenza in our Influenza (flu) season health feature.

Visit ImmunizeBC: Frequently asked questions about influenza vaccines for evidence-based immunization information and to find answers to your immunization questions.

General information on influenza

1. What causes influenza?
Influenza is an infection of the respiratory system, caused by an influenza virus. (close)
2. What are the symptoms of influenza?
Influenza symptoms can vary from mild to severe, and include fever, headache, muscle pain, runny nose, sore throat, extreme tiredness and cough. Children may also experience nausea, vomiting or diarrhea. Although infections from other viruses may have similar symptoms, symptoms caused by the influenza virus tend to be worse and start more abruptly. (close)
3. How is influenza spread?
Influenza spreads easily from person to person through breathing, coughing, and sneezing. The virus can also spread when one person touches tiny droplets from another person's cough or sneeze on an object or person, and then touches their own eyes, mouth or nose before washing their hands. An infected person can spread the influenza virus even before feeling sick. An adult can spread the virus from about 1 day before to 5 days after symptoms start. Children can spread the virus up to 21 days after symptoms start. (close)
4. How long does it take to show signs of influenza after being exposed?
Symptoms can begin about 1 to 4 days, or an average of 2 days, after a person is first exposed to the influenza virus. Fever and other symptoms can last up to 7 to 10 days, but the cough and weakness may last 1 to 2 weeks longer. (close)
5. What is the home treatment for influenza?
If you get sick with influenza, home treatment can help ease symptoms. Follow the self-care advice below: Get plenty of rest Drink extra fluids to replace those lost from fever Avoid smoking and ask others not to smoke in the house Breathe moist air from a hot shower or from a sink filled with hot water to help clear a stuffy nose Anti-influenza drugs or antivirals are available by prescription. For them to work best, you must take them within 48 hours after your symptoms start. If you take them within 12 hours, they will shorten symptoms by about 3 days. If you take them within 2 days from the start of your symptoms, your symptoms will be shortened by about 1.5 days. Non-prescription cough and cold medications are available for relief of influenza symptoms. These medications are not recommended for children under 6 years old. (close)
6. How do you prevent influenza?
You can reduce the risk of getting influenza and spreading it to others by: Getting an influenza vaccine Staying home when you are ill Washing your hands regularly Cleaning and disinfecting objects and surfaces that many people touch Promptly disposing of used tissues in the wastebasket or garbage Coughing and sneezing into your shirt sleeve rather than your hands (close)
7. What are some risks or complications of influenza?
Influenza can be mild, but it can also cause serious illness and can lead to hospitalization and even death. A person with influenza is at risk of other infections, including viral or bacterial pneumonia, which is an infection of the lungs. Everybody is at risk of getting sick from influenza, but very young children and seniors, 65 years and older, are especially vulnerable and at highest risk of serious illness from influenza. If you are pregnant or if you have certain medical conditions, you are also at very high risk. For people with chronic health problems, lung or heart diseases, or weakened immune systems, influenza can lead to pneumonia, respiratory failure and other complications. (close)
8. When should I see a health care provider?
Consult your health care provider early if you develop influenza-like symptoms and you have a condition that puts you at very high risk of severe disease and complications. You should also call your health care provider if you get new or worsening symptoms, including shortness of breath or difficulty breathing, chest pain, or signs of dehydration (dizziness when standing or low urine output). (close)

Vaccine recommendations

1. How do influenza vaccines work?
The influenza vaccines work by helping your body recognize the influenza virus by creating antibodies in the body about two weeks after you get the vaccine. These antibodies and other parts of your immune system provide protection against infection if you get exposed to it later that season. An influenza vaccine is needed every year for two main reasons: the influenza viruses are constantly changing, and the protection the vaccine gives you declines over time. Each year, the viruses used to make the vaccine are reviewed and updated as needed. This helps protect you against the viruses that are more likely to circulate that year. (close)
2. What is in the influenza vaccine?
The 2023-24 seasonal influenza vaccines protect against 4 different influenza viruses: A/Victoria/4897/2022 (H1N1)pdm09-like virus A/Darwin/9/2021 (H3N2)-like virus B/Austria/1359417/2021-like virus B/Phuket/3073/2013-like virus (in quadrivalent vaccines only) The A/Victoria strain was not contained in the 2022/23 season vaccines. There are several inactivated influenza vaccines available in B.C. The inactivated vaccines are made of killed influenza viruses or of inactive parts of influenza viruses and are given by injection. Another influenza vaccine, the Live Attenuated Influenza Vaccine (the nasal spray vaccine, also known as LAIV or Flumist®) is made of live weakened influenza viruses and is given as a nasal spray. It is intended for those eligible individuals 2-17 years of age (inclusive). Publicly-funded influenza vaccines in B.C. for the 2023/24 season include: FLUAD® FLULAVAL® TETRA FLUMIST® QUADRIVALENT FLUZONE® QUADRIVALENT FLUZONE® HIGH-DOSE QUADRIVALENT To learn more about this year’s seasonal influenza vaccine, visit ImmunizeBC: Influenza and BC Centre for Disease Control: Intended Use of Influenza Vaccines. (close)
3. Who should get the influenza vaccine?
Everyone 6 months of age and older should get a yearly influenza vaccination with rare exception. Vaccination is especially important for people who are at high risk of serious illness from influenza (such as young children, pregnant women, seniors 65 years and older, and people with certain medical conditions) and those able to transmit or spread influenza to those at high risk. This fall and winter, everyone in British Columbia who is six months of age and older can get the influenza vaccine free of charge. To learn more about the influenza vaccine, see HealthLinkBC File #12d Inactivated influenza (flu) vaccine. (close)
4. Who should not receive the influenza vaccine?
Speak with your health care provider if you: Had a life-threatening allergic reaction to a previous dose of influenza vaccine, or any part of the vaccine (people with egg allergies can be safely immunized) Developed Guillain-Barré Syndrome (GBS) within 6 weeks of getting any influenza vaccine without another cause being identified (close)
5. Should my child under 6 months old get the vaccine?
Children less than 6 months of age should not get the vaccine because it is not known to be effective at this age and no vaccine is approved for use for this age group. (close)
6. I’m not feeling well. Should I get the vaccine?
In general, it's safe for you to get immunized even if you are recovering from an illness. However, stay home if you are recovering from an illness that can spread from person to person so you're not putting others at risk of infection when you come for your vaccine. (close)
7. What is the Influenza Prevention Policy?
B.C. has an Influenza Prevention Policy to protect high risk people from getting influenza. Those at high risk include infants, young children, pregnant women, seniors, and people with certain medical conditions. Health care workers are required to be immunized against influenza or wear a mask when they are in patient care areas during the influenza season. Students, volunteers and visitors to health care facilities and other patient care locations are also expected to wear a mask if they did not get an influenza vaccine. (close)

Populations at highest risk (infants, young children, pregnant women, seniors, people with certain medical conditions)

1. Can I get the influenza vaccine while I’m pregnant?
The inactivated influenza vaccine or flu shot is considered safe at any stage of pregnancy. If you are in the second half of pregnancy or later, you are at higher risk of hospitalization due to influenza, especially during the third trimester. If you are pregnant and have a chronic medical condition, you are at much higher risk of serious influenza complications and should be immunized. If you are pregnant or intending to become pregnant, you should receive the inactivated influenza vaccine, which contains killed influenza viruses or inactive parts of influenza viruses that cannot cause infection. (close)
2. Can I get the influenza vaccine while breastfeeding?
It is safe for babies to breastfeed after mothers receive the influenza vaccine. (close)
3. Can my 3-month-old be vaccinated?
Children less than 6 months of age should not get the vaccine because it is not known to be effective at this age, and no influenza vaccine is approved for use in this age group. (close)
4. Should seniors get the influenza vaccine?
As people age, they may be at much higher risk of complications from influenza. For this reason, seniors aged 65 years and older are strongly advised to get an inactivated influenza vaccine each year. (close)
5. Should individuals with neurologic or neurodevelopment conditions get the influenza vaccine?
It is recommended for children and adults with neurologic and neurodevelopmental conditions to get the influenza immunization. (close)

Vaccine safety

1. Is the influenza vaccine safe?
The influenza vaccines are safe. You may have redness, soreness or swelling where the vaccine was given. Some people, especially those who get the vaccine for the first time, can have a headache, muscle aches or tiredness. (close)
2. Can I or my child get the vaccine if either one of us has a cold?
In general, it's safe for you to get immunized if you or your child are recovering from an illness. However, stay home if you or your child are recovering from an illness that can spread from person to person so you're not putting others at risk of infection when you come for your vaccine. (close)
3. I am allergic to egg, is it ok to get the vaccine?
People with egg allergies can be safely immunized with the inactivated influenza vaccine. Most people with allergies can get an influenza vaccine without any problems. However, if you have had a severe allergic reaction to a previous dose of influenza vaccine or to any part of the vaccine, talk to your health care provider. You may need to be tested for allergies before being immunized. (close)