(Note: This article presents general information on seasonal influenza. In the current COVID-19 pandemic, it more important than ever to be vaccinated against flu so as not to add more strain to our health care system.)

“It’s just a bit of flu”. How often have you heard that? Few people realize that influenza (the common “flu”) takes an enormous toll on our society. In Canada, for example, flu causes 50,000 hospitalizations per year culminating in more than 5000 deaths. Over 1.5 million workdays are lost annually. That’s more than “a bit of flu”!

Influenza is endemic in our society, meaning there are always some cases. It is during pandemics – when a strain of the virus causes worldwide infection – that we are most vulnerable. During the 1918 – 1919 pandemic a third of the world’s population was infected and there were in excess of 675,000 deaths in the United States with 50 million fatalities worldwide!

What exactly is flu?

So what is flu and how do you know if you have it?

First, flu is a respiratory illness. People frequently use the term “flu” to refer to a viral type of illness that causes stomach cramping, nausea, vomiting and sometimes diarrhea. Fever may or may not be present and the whole unpleasant affair usually only lasts 24 hours. This is not influenza. This is gastroenteritis.

For those of you who relish the technical information (budding microbiologists and geneticists), influenza is a single-stranded RNA virus, which is grouped into 2 subtypes based on surface proteins. It is the two types of surface proteins* which mutate resulting in minor changes (drifts) or major changes (shifts). When a major change occurs, a pandemic develops.

The flu virus infects the lining of our major airways. It is spread by inhalation of infected expelled cough/sneeze droplets as well as by touching contaminated surfaces where the virus has landed. Flu virus can live for several hours on surfaces such as doorknobs and phone receivers.

Even so, with all that spreading, approximately 50% of people will have no symptoms and will develop immunity.

For the rest of us sad sacks who catch “the bug”, the symptoms of flu include: headache, sore throat, cough and myalgias (muscle aches) along with fever. If you have a fever and any 2 of these symptoms, you likely have flu.

The incubation period for influenza is 24 to 72 hours. Adults with influenza will remain infectious for 3 to 5 days after onset of symptom. Children can remain infectious for up to a week after onset.

Family doctors have a 70% chance of accurately diagnosing flu if the above symptoms are present and flu is in the community. School age children get flu 2 weeks early than adults.

The acute symptoms typically last 3-5 days but the malaise can linger for up to 2 weeks! It can really knock the wind right out of your sails!

Most morbidity (sickness) and mortality (death) associated with flu is due to secondary complications that occur. Pneumonia, congestive heart failure, ear infections and irregular heart rhythms can arise when the immune system is compromised with a bout of influenza. People with underlying chronic ailments such as asthma, COPD**, cystic fibrosis, diabetes and coronary artery disease are particularly susceptible to developing serious illness and death.

The mortality rates are highest in the very young (1 in 5,000 infants) and those over 75 years. The death rate for influenza alone in Canada is 500 to 1500 cases per year. When you look at influenza and pneumonia, which is a common complication of influenza, the combined death toll is more than 8,000 people a year.

How do I prevent flu?

I’m glad you asked! Aside from hand washing with soap and water, (or if none is available, alcohol based hand-sanitizers), staying away from ill people, and sanitizing high traffic areas and surfaces, flu shots are the single most effective preventative treatment.

There is very good evidence that anyone – not just the high risk individual*** – can benefit from a flu shot – especially if you consider absenteeism from work or school to be a complication worth preventing. (CDC Prevention of Flu.)

Everyone over 6 months of age should get a flu shot, with few exceptions. Even “egg allergy” is no longer a reason to abstain from annual flu vaccination. Remember that the flu shot is a killed virus. You cannot get the flu from having a flu shot.

The vaccine’s efficacy varies from year to year based on the virulence of the mutating virus. The vaccine is extremely safe and is well tolerated. Flu season is in the winter. Every spring, a decision is made as to which strains of virus to include in the annual serum. In BC the vaccine is usually available in mid-October and is effective for up to 6 months.

For a complete review of influenza I suggest you check out the CDC (Centre for Disease Control) website: CDC Influenza.

Antiviral drugs currently used in Canada for the treatment and prevention of seasonal influenza are oseltamivir (Tamiflu®), which is administered orally and zanamivir (Relenza®), which is inhaled. These medications are effective against both influenza A & B.

Relenza is administered via disk inhaler and a much lower dose is used. It delivers the drug directly to the site of infection (the airways and lungs) and there are virtually no side effects. If started within 30 hrs of symptom onset, this drug can reduce the major symptoms by 1.5 – 2.5 days. It is pricey (about $70 for a 5 day supply) but for some, getting back to work an extra day or two early is definitely worth the expense.

A 5-day supply of Tamiflu (oral medication) is priced about $50. It too, is effective for easing flu symptoms. Both of these medications are available with a prescription from your doctor.

There is a lot of benefit to be gained by getting your annual flu shot to protect yourself and the more vulnerable members of your family from this disease.

Follow this link for a reliable FLU GUIDE that should answer any further questions you may have.

Another excellent resource with Canadian facts and figures can be found HERE.

Stay healthy. Prevent flu!

* The 2 proteins are: hemagglutinin (HA) and neuraminidase NA)
** COPD – chronic obstructive pulmonary disease
*** “High Risk” individuals are the very young, the very old, the debilitated, the immunocompromised and healthcare workers

Reference: New Approaches to Management of Influenza; Dr. Lindsay Lawson; St. Paul’s Hospital 45th Annual CME Course, November, 1999.

Dr Shannon Lee Dutchyn, MD, CCFP, FCFP