Is the flu virus mutating dangerously?

Despite a huge amount of information about the H1N1 virus, Canadians still have questions about diagnosis, treatment and how to best respond.

Join André Picard, The Globe and Mail's public health reporter, as he answers questions from readers about the pandemic.

L eave your questions here using the Globe's comment function.

For more answers, see the Globe's previous Q&A's on the virus , the vaccine and parents' questions .

Wednesday, Nov. 25

Q - I saw a story that said the H1N1 was mutating. Does that mean that drugs and the vaccine won't work any more and the flu will be more deadly?

A: There are a couple of issues here.

First, there have been a number of stories about H1N1 developing resistance to Tamiflu, an antiviral drug. This resistance can occur when the drug is misused - when patients don't take the full course of treatment (with Tamiflu that is twice daily for five days.) These resistant strains can spread, making influenza more difficult to treat, but the vaccine still works to protect you against infection.

The Norwegian Institute of Public Health announced last week that it has identified a "potentially significant mutation" in three patients, and that generated a lot of media attention. According to the World Health Organization, the same mutation has been found in China, Japan, Brazil, Ukraine, Mexico and the U.S.

Influenza viruses mutate frequently. That's why you need a flu shot every year - to protect against new strains. During flu season, sporadic cases are expected and not worrisome unless the mutated virus starts spreading person-to-person. So far, there is no evidence that has occurred. So there is no concern about the vaccine not working, at least in the immediate future.

Mutated flu viruses are not necessarily more deadly. In fact, they are often variations (or cousins if you will) of earlier flu viruses so many people can have partial immunity. We have seen this phenomenon with H1N1: Even though it is a novel strain - and thus was believed to have the potential to infect everyone - most people born prior to 1957 have partial immunity. Why? Because, between 1918 and 1957 many strains of H1N1 flu viruses circulated so people developed immunity.

While there is no doubt that H1N1 will mutate, the concern of public health officials is when and how. A major mutation that created a new strain of influenza that spread person-to-person would render the vaccine ineffective but that doesn't seem too likely as H1N1 activity peaks.

The nightmare scenario would be H1N1 (swine flu) hooking up with H5N1, a bird flu that sparked pandemic fears a few years back and which continues to be quite deadly. If those two flu viruses were to swap genetic codes it could create a superbug. Earlier today, a researcher told Reuters news agency that is a distinct possibility because, in China, both viruses are circulating.

"China, as you know, is different from other countries. Inside China, H5N1 has been existing for some time, so if there is really a re-assortment between H1N1 and H5N1, it will be a disaster," said Dr. Zhong Nanshan, director of the Guangzhou Institute of Respiratory Diseases in China's southern Guangdong province.

Friday, Nov. 20

Q: Months ago there were stories about the global pandemic of swine flu. Now all we read about is the flu in Canada. What's going on in the rest of the world?

A: According to the World Health Organization, H1N1 influenza has been reported in 206 countries and overseas territories. There have been 6,770 laboratory-confirmed deaths. The WHO has recorded more than 525,000 cases of H1N1 worldwide but notes that many countries have stopped counting individual cases. (In Canada alone, for example, an estimated 3.5 million people have been infected with the flu.)

In North America, there is active and geographically widespread disease. The flu continues to spread in Northern and Eastern Europe, particularly in parts of the former Soviet Union. Influenza seems to have peaked in Western Europe, such as in the United Kingdom. In Central and Western Asia, flu activity is waning but there are still sporadic outbreaks, such as in Afghanistan and Israel. In East Asia, H1N1 activity continues but is not particularly intense, with the exception of Mongolia. In China and South East Asia there are only small numbers of H1N1 cases and seasonal influenza (H3N2 in particular) is spreading. In the southern hemisphere, where it is no longer flu season, the spread of H1N1 has slowed considerably, with the exception of Peru and Colombia. Transmission of H1N1 has declined sharply all over southeast Asia, with the exception of Sri Lanka. In Africa, there is little flu activity; there have been twice as many H1N1 deaths in Canada is in all of Africa.

Thursday, Nov. 19

Q: If enough people get the flu and get vaccinated then there won't be anyone who can spread the flu, right? So I can avoid getting vaccinated and still be safe. Do you follow what I'm saying?

A: The scientific term for the idea you are describing is herd immunity. When a majority of people (or animals) in a group are immune to a disease, the disease cannot find a viable host to take hold so it can't spread. Therefore, even if you have not been infected or vaccinated, you effectively get immunity without paying the price (the price being a needle or an illness). The problem is that for herd immunity to kick in, anywhere between 50 and 90 per cent of the population needs to immune and practice good hygiene. (No doubt you have heard the admonitions to hand washing and sleeve-coughing.) With influenza herd immunity kicks in when about 80 per cent of the population is immunized. But even that goal is ephemeral because influenza viruses mutate easily and often, so herd immunity is virtually impossible to attain. Currently in Canada, about 20 per cent of the population has been vaccinated against H1N1 and about 10 per cent has been immunized naturally through illness. That is far short of the 80 per cent threshold that would allow you to be a freeloading member of the heard so your idea, while clever, won't be too effective.

Wednesday, Nov. 18

Q: We've been hearing about the flu pandemic and the importance of vaccination for weeks. But none of the stories seem to say how many people have actually been vaccinated, how many had the flu and how many died. What's the deal?

A: According to the Public Health Agency of Canada, approximately 20 per cent of the population has been vaccinated against H1N1 influenza so far. That is about 6.6 million people - or the number of doses of vaccine distributed as of Nov. 07. (It takes about a week for all the vaccine to be used after delivery.)

By the end of this week the number of vaccine doses delivered will have surpassed 10 million.

An estimated 10 per cent of the population has contracted H1N1 flu so far, according to PHAC. Not all 3.3 million or so of them have been tested. The estimate is based on sentinel testing (or sampling, if you prefer) around the country. Infectious disease experts estimate that, before all is said and done, as many as 10 million Canadians will get sick with H1N1 flu, roughly the same as a 'normal' flu season.

As of Nov. 07, a total of 3,764 people have been hospitalized with severe H1N1 influenza, including 606 people admitted to intensive care. Hospitalizations are most common in the under-20 age group, which is unusual for influenza. Those admitted to ICU are principally in the under 5 and 45-64 age group, which is also unusual for influenza. While relatively few seniors are contracting H1N1 (they have some natural immunity from exposure to similar strains of the virus), they have the highest death rate when they do fall ill.

To date, there have been 198 deaths, the bulk of them in Ontario and Quebec. Here is a breakdown:

Province/Territory	Deaths (as of Nov. 17/09)
British Columbia	29
Alberta	20
Saskatchewan	8
Manitoba	8
Ontario	61
Quebec	58
New Brunswick	2
Nova Scotia	3
Prince Edward Island	0
Newfoundland and Labrador	7
Yukon	1
Northwest Territories	0
Nunavut	1
Total	198

Tuesday, Nov. 17

Q: I read that there's worldwide shortage of Tamiflu. But I also read that Canada has a huge stockpile. Can you tell me who's getting this drug and why?

A: As part of the pandemic preparedness plan, Canada purchased 55 million doses of the antiviral drugs oseltamivir (Tamiflu), and zanamivir (Relenza). The medications have been distributed to provinces and territories on a per-capita basis, and the medication can be prescribed by physicians.

Antivirals are used to slow the replication of the H1N1 virus to lessen symptoms and reduce the spread of illness to others. But they have to be used early - within 48 hours of onset of symptoms - to be effective.

The Public Health Agency of Canada has promoted the prudent use of antivirals, so they are used primarily for treating people with severe illness, not people who are only mildly ill. Antivirals are also used more liberally for those at high-risk of complications like young children and people with chronic health conditions.

Tamiflu can be used by people of all ages; the medication comes in pill form and there is a liquid form for children. Relenza is taken as an inhalation powder (in a puffer similar to those used by some people with asthma). It is not recommended for children under the age of seven.

In Canada, antiviral drugs are used also exclusively as a treatment, not as prophylaxis (to prevent the spread of the flu). The exception is care facilities and nursing homes populated by people at high-risk of complications. In those settings, antiviral drugs are used routinely to prevent he spread of seasonal flu and they are prescribed at the first sign of H1N1 in a closed facility.

When prescribed, both Tamiflu and Relenza are taken twice daily for five days. (The pediatric dose of Tamiflu is about half the adult dose.) The medications cost about $4 a dose.

Monday, Nov. 16

Q: Can you clarify who should get what kind of vaccine and what dose. With all the changes I can't keep track anymore.

A: Here are the up-to-date recommendations from the Public Health Agency of Canada for use of the H1N1 vaccine:

Age 0-5 months - vaccine not authorized for use

Age 6 months to 3 years - two half-doses of adjuvanted vaccine

(with at least 21 days between the two half-doses)

Age 3 to 9 years - Healthy children - one half-dose adjuvanted vaccine, or one dose unadjuvanted

Age 3 to 9 years - Children with chronic medical conditions - two half-doses of adjuvanted vaccine

(with at least 21 days between the two half-doses)

Healthy people age 10 to 64 years - one dose either adjuvanted or unadjuvanted vaccine

People aged 10 to 64 years with weakened immune systems - one dose adjuvanted vaccine

People aged 65 years and over - one dose adjuvanted or unadjuvanted vaccine

Pregnant women - one dose unadjuvanted vaccine

Co-administration:

* H1N1 flu vaccine may be administered at the same time as seasonal flu vaccine and other vaccines, but they should be administered in separate limbs.

Sunday, Nov. 15

Q: I am an immigrant. My parents are coming for a visit. The vaccine is not available in their home country so can they get it when they're here? I don't expect it to be free; I'm willing to pay.

Q: I am a Canadian expat residing in a country overseas that does not offer the H1N1 vaccine. Would I be eligible for a vaccine when I return to Canada for a visit?

A: The H1N1 vaccine is available, free-of-charge, to all Canadian residents. If you have a provincial health card, you can get the vaccine, according to the now-well-known priority lists. (Most provinces, have already vaccinated pregnant women, babies and young children, and adults and children with health conditions that place them at higher risk. Now they are vaccinating healthy children age 5-18, which will be followed by healthy adults and then healthy seniors.) Because of line-ups and shortages of vaccine, most clinics also demand proof of local residency - this is to avoid "clinic-shopping" which occurred when there was the first big rush for vaccination.

The entire stock of H1N1 vaccine in Canada, 50.4 million doses of adjuvanted and non-adjuvanted vaccine, was purchased by the federal government. It is not available for purchase by individuals.

A much-publicized story, in which a man pretending to be a nurse offered to sell a vial of H1N1 vaccine on , has been exposed as a hoax. Public health officials warn that vaccine offered for sale online is almost certain to be bogus.

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