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Is the flu actually an epidemic? André Picard tackles your flu questions Add to ...

We asked for your questions about the flu sweeping the country; The Globe's health reporter André Picard found answers.  (Have a question? Submit it in the form below.)

What’s the difference between norovirus and the flu – or are they the same? Wayne, St. Thomas, Ont.

Influenza is a virus and norovirus is a virus but otherwise they are very different. The flu is a respiratory illness – it attacks the lungs, causing you to cough and have trouble breathing. Norovirus – also known as vomiting disease – attacks the gut and causes you to, well, you probably guessed by the name. The main reason hospitals are overwhelmed this winter is because both flu and norovirus have hit simultaneously. There is a vaccine to protect against the flu, but not one to protect against norovirus.

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How can you distinguish flu and food poisoning? – Brian, Bowmanville, Ont.

Typical symptoms of food poisoning are nausea, vomiting, abdominal cramping and diarrhea that come on quite suddenly. Typical influenza symptoms are fever, cough and chills, which come on suddenly. So they are very different. What is more difficult is distinguishing food poisoning from norovirus. That’s because you can catch norovirus from contaminated food or water, as well as from other people.

I think I have the flu; my husband says it’s just a bad cold. How can I tell them apart? – Alice, Mississauga, Ont.

It’s all about severity of symptoms. A cold will cause sneezing, a stuffy or runny nose, sore throat and hacking, phlegmatic cough. With influenza you will usually have a fever, muscle aches and chills, and the cough is dry. Both are unpleasant and the treatment is the same: rest and drink plenty of fluids.

I got a flu shot but now I have horrible stomach flu. Why didn’t the vaccine work? Tracy, Calgary

The flu vaccine protects against infection with three strains of influenza. (One of those strains, H3N2, is the one that is making many Canadians sick.) However, there are many other viruses and bacteria that circulate in the winter and the vaccine will not protect against those. Influenza does not normally cause stomach problems in adults (it can in children) so it is unlikely you have the flu. The term “stomach flu” is a misnomer but it’s often used to describe gastrointestinal illnesses like norovirus, which is circulating widely this year, particularly in Western Canada. So your flu shot may well have worked, but another type of bug made you sick.

Should I give my four-year-old and two-year old the flu shot? Does it really work on young children? – Cindy, Markham

The National Advisory Committee on Immunization recommends that all Canadian over the age of six months get the flu shot. The traditional flu shot works for children, but a nasal version of the vaccination is even more effective for kids. (The nasal spray is not yet available in all jurisdictions.) What is important to remember is that influenza is particularly dangerous for children under the age of five because they are susceptible to pneumonia (a life-threatening inflammation of the lungs). Hundreds of young children are hospitalized with influenza in Canada each year – last week alone 69 Canadian children were hospitalized with severe flu symptoms – and there are, sadly, a handful of deaths. That is why some infectious disease specialists are lobbying for annual, school-based flu vaccination programs.

Can I still get the flu if I’ve had the flu shot? Raymond, Richmond, B.C .

Yes you can still get the flu if you’ve had the flu shot. The vaccine protects against three strains, but there are others circulating. In addition, even when the vaccine is a match, it does not confer 100 per cent protection. Dr. Thomas Frieden, director of the U.S. Center for Disease Control and Prevention, said Friday that the current vaccine is 62 per cent effective against current strains. That is quite different from basic childhood vaccines, which are more than 90 per cent effective. Without wading too deeply into the science, there are a couple of reasons for this: 1) it take a couple of weeks for the flu vaccine to create an antibody response and people remain susceptible in that time and 2) people don’t always mount a strong response to the vaccine, particularly if they have a compromised immune system.

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