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Pandemic disease experts are preparing for a possible second wave of the swine flu. ((Natacha Pisarenko/Associated Press))

Mexican authorities in April 2009 reported they were investigating a new strain of swine influenza. The outbreak had spread quickly in the country, killing more than 100 people. Two months later, in June 2009, the World Health Organization declared a swine flu pandemic — the first time a global flu pandemic had been declared in 41 years.

As the number of cases continue to slowly increase, pandemic disease experts are preparing for a possible second wave. Canada has a stockpile of anti-viral drugs to treat about one-quarter of the population and the Public Health Agency of Canada will stockpile ventilators, eventually keeping 500 on hand. Still, there is uncertainty in how the spread of the swine flu will play out.

"No one can give you an accurate play-by-play, guaranteed, certified guide on what the pandemic is going to look like," said Dr. Michael Gardam, director of infectious disease prevention at Ontario's Public Health Agency.

Here is a summary of frequently asked questions about swine influenza, prepared using information from the Public Health Agency of Canada, the World Health Organization, and the U.S. Centers for Disease Control.

What is new influenza A (H1N1)

Swine flu (also referred to as novel H1N1 virus) is a new virus that hasn't spread before among humans. The virus was first detected in people in March 2009.

Viral vocabulary

Epidemic: A disease that occurs in an unusually high number of individuals in a community at the same time. The U.S. Centers for Disease Control says that to epidemiologists the terms "epidemic" and "outbreak" basically mean the same thing, and "outbreak" is often used to avoid sensationalism. The World Health Organization (WHO) says, "A disease outbreak is the occurrence of cases of disease in excess of what would normally be expected in a defined community, geographical area or season. An outbreak may occur in a restricted geographical area, or may extend over several countries. It may last for a few days or weeks, or for several years." SARS was considered an epidemic in Canada.

Pandemic: A very widespread, often global, disease. According to the World Health Organization, "An influenza pandemic occurs when a new influenza virus appears against which the human population has no immunity, resulting in epidemics worldwide with enormous numbers of deaths and illness."

Endemic: A disease that is constantly present, usually in low numbers in a population.

Why is this strain of flu causing so much concern?

It's a brand new mutation that's never been seen before. That's why it's not just hitting people in the highest risk groups — those over 65 and younger than two.

Flu is not usually a huge worry among the vast majority of healthy people because over the course of our lives, we are exposed to several flu strains. We develop some immunities. When we get the flu, we'll normally just feel really awful for a week or two. But when you have no immunities at all to a new strain, normally healthy people face as much of a risk as higher risk groups.

How does swine flu kill?

Swine flu — just like any other flu — is a respiratory infection. It exploits a weakened immune system to attack major organs — especially your lungs. When it gets into your lungs, it can lead to pneumonia, which can kill you. The flu can also cause secondary infections in your body — any of which can lead to failure of vital organs and death.

Can people catch swine flu from eating pork?

No. Swine flu viruses are not transmitted by food. You cannot get swine flu from eating pork or pork products. You won't get swine flu from handling uncooked pork either. You can get sick from putting uncooked or undercooked pork in your mouth, but you won't get swine flu.

On May 7, 2009, the World Health Organization once again said that it is generally safe to eat pork. The world health body said existing sanitary and animal health checks were sufficient to safeguard the food supply against the swine flu virus. The statement came a day after an official said it was possible the virus could survive freezing if a slaughtered animal was sick. However, it is illegal to slaughter a sick or dead animal.

If you eat meat from an animal that was sick or had died before it was slaughtered you are taking major risks, the least of which is swine flu.

It's also impossible to catch swine flu from eating fruits and vegetables imported from Mexico or any other country that has recorded cases of swine flu. Swine flu — like all influenza viruses — is not a food-borne illness.

What are the symptoms of swine flu in humans?

The symptoms of swine flu in people are expected to be similar to the symptoms of regular human seasonal influenza and include fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea.

  • Swine flu is caused by type A influenza virus and gives pigs the flu. Swine flu viruses cause regular outbreaks of flu in pigs but death is infrequent.
  • Right now, there are four main influenza type A swine flu viruses that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1.
  • Swine flu viruses do not normally infect humans. However, sporadic human infections have occurred. Most commonly, these cases occur in persons with direct exposure to pigs, such as children near pigs at a fair or workers in the swine industry. In addition, there have been documented cases of one person spreading swine flu to others

(Source: U.S. Centers for Disease Control and Prevention)

How does swine flu spread?

Influenza viruses can be directly transmitted from pigs to people and from people to pigs. Human infection with swine flu viruses are most likely to occur when people are in close proximity to infected pigs, such as in pig barns and livestock exhibits at fairs.

Human-to-human transmission of swine flu can also occur. This is thought to occur in the same way as seasonal flu occurs in people, which is mainly person-to-person transmission through coughing or sneezing of people infected with the flu virus. People may become infected by touching something with flu viruses on it and then touching their mouth or nose.

Is there a vaccine to treat swine flu?

A vaccine against H1N1 is being prepared and is expected to be tested in September. The U.S. The Public Health Agency of Canada says early research shows two prescription antiviral drugs — oseltamivir (Tamiflu) and zanamivir (Relenza) — can be used to treat this strain of the swine flu. PHAC notes however that antivirals should only be used in moderate to severe cases and if a patient is in danger of complications.