The H1N1 virus has begun to spread in earnest and the high-profile death of a 13-year-old Toronto boy has awakened the public to the potential dangers of the virus. Many readers are worried and looking for clear information about the threat posed by H1N1 influenza. The Globe and Mail's public health reporter, André Picard, tries to clear up the "conflusion" by answering reader questions. Mr. Picard has also answered your questions on the and questions from parents about
Please note that this information is not medical advice. Rather, it is an attempt to synthesize and explain in plain language information from public health officials and medical experts.
Question: What's the difference between H1N1 flu and the seasonal flu?
Answer: The formal name for the strain that has captured our attention is influenza A/H1N1/California (H1N1 or swine flu for short). Various strains of influenza circulate every year; they are usually mutated forms of earlier flu bugs, meaning many people have full or partial immunity. H1N1 is different - it jumped directly from animals to humans. That means it has the potential to infect and sicken a lot more people.
Q: It's called swine flu. Does that mean we get it from pigs?
A: Many animals and birds get the flu, but those strains do not usually pose a threat to humans. At some point earlier this year H1N1 jumped from a pig to a human. But the virus now has nothing to do with pigs; it spreads human-to-human. Early on, the virus was dubbed swine flu because it resembled a strain that circulates in pigs. Genetic testing later showed that swine flu actually is a mixture of two types of swine flu, an avian flu and a human flu.
Q: What do the all the letters in influenza A H1N1 stand for?
A: There are three types of influenza viruses: A, B, and C. Only type A influenza can cause a pandemic and it causes the most serious illness in humans. Influenza A viruses are classified by two proteins on their surface: H for hemagglutinin and N for neuraminidase. There are 16 H subtypes: H1, H2 and H3 are found in human influenza viruses. There are at least nine subtypes of neuraminidase; N1 and N2 are associated with humans. Influenza B can cause epidemics but not pandemics; it causes illness, but tends to be less deadly. Influenza C causes mild illness.
Q: So what are my odds of getting the flu?
A: In an average year, 10 to 20 per cent of Canadians get sick with the flu. With a pandemic strain like H1N1, that number could jump to 30 to 50 per cent. According to mathematical modelling done as part of the Canadian Pandemic Influenza Plan, a new strain could kill between 11,000 and 58,000 Canadians in a period of six to eight weeks. It could also result in the hospitalization of 35,000 to 138,000 people and leave 4.5 million to 10.6 million others too sick to work, which would have a devastating economic impact. But that's a worst-case scenario.
Q: Is H1N1 actually more deadly?
A: There was a long-running assumption that a pandemic strain of influenza would be more deadly than seasonal flu. So far, H1N1 is not proving more deadly. If anything, it will probably be less lethal than a seasonal flu. But remember, a run-of-the-mill seasonal flu kills an estimated 4,000 to 8,000 Canadians each year.
Q: Is the risk of contracting the flu and dying the same for everyone?
A: Anyone can contract the flu - seasonal or H1N1 - unless they have some immunity, either from prior exposure or vaccination. But, generally speaking, the healthier a person is, the better they can fight off infections. Seasonal flu usually kills the frail elderly and others with chronic health conditions. H1N1 is unusual in that it is killing younger people (under 50), some of them quite healthy prior to contracting the flu. Two-thirds of those dying of H1N1 are women, a fact that researchers can't really explain. People born prior to 1957 (when a similar flu strain circulated) seem to have partial immunity so a lot fewer seniors are getting sick than with the seasonal flu. However, when older people do contract H1N1, the death rate is quite high.