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Column originally published Jan 30, 2018
Column last revised/updated on Apr 9, 2018

You Can Prevent Influenza Infection

Question: I am worried about the recent outbreak of influenza across Canada. Our five-year-old son has severe asthma; he was hospitalized twice last year. All of us got the flu shot in November. Our son goes to kindergarten. Is there anything more that we can do to prevent him from getting sick with this flu?


You are right, it appears that we are getting into a serious influenza epidemic this winter.  Large outbreaks have occurred in many provinces, especially affecting seniors.  Children are not spared, but fortunately, very few have died.

In previous years, almost all influenza infections during the early part of flu season are caused by influenza A.  This year, however, is quite different.  Although about 70% of infections are caused by influenza A (H3N2 subtype), the rest belongs to influenza B.  Most of the time, influenza B infections tend to start later in the flu season.  The early emergence of influenza B can be the reason why we are seeing such a large outbreak of influenza now.

The good news is that both influenza A (H3N2) and influenza B strains circulating now are very similar to those covered by the flu shot that you received in November.  This does not mean that you and your family will not get infected.  This is because the immunity induced by the flu shot is not completely protective.  If you come into contact with someone who got quite sick and in the early phase of illness, you will have a lot of influenza virus infecting you.  This can overwhelm the immunity in your body.

The good news is that your body can start fighting the virus much faster and more effectively.  You won’t be down and out for nearly as long as those who didn’t get the vaccine.  Also, your body will produce less virus that can spread to those around you.  Your chance of infecting your son is less because both of you got the flu shot.

However, not much can be done to prevent your son from getting infected in school.  Many of his classmates likely did not get the flu shot.  For children with no underlying medical problem, it can be a mild infection, although some children can still get complications like ear infection, sinus infection, or pneumonia.  Some can get dehydrated from repeated vomiting.

Those with asthma, diabetes, cancer, or other underlying immune deficiencies can become extremely sick.  If your son requires daily prevention medicine for his asthma, make sure he gets it.  If he starts early symptoms of infection, get in touch with your family doctor or paediatrician right away.  There is a medicine called Tamiflu that he can take; it is an antiviral medication (like antibiotics for bacterial infections) that can cut short the course of influenza and reduce complications.  You likely need to increase his asthma medicine also.  Keep in close contact with his doctors, you may be able to avoid another admission to the hospital.  Your doctor may even advice the rest of the family to take Tamiflu for prevention.

When he is sick, make sure he gets a lot of rest and drinks plenty of fluid.  He can take acetaminophen for fever and pain, but never give him aspirin: this can cause another serious complication.

If any of you have influenza-like illness, it is important to stay at home instead of going to work or to school.  This will reduce the chance of spreading the virus to others.  If everyone heeds this suggestion, the spread of influenza will not be as bad as what is happening now.