Health workers prepare to fumigate against the swine flu at a subway station in Mexico City on Saturday. (Rodrigo Abd/Associated Press)

Health officials in Toronto say they're concerned that people are unnecessarily worried about swine flu and have been trying to reassure residents it is not a repeat of the 2003 SARS outbreak.

SARS killed 44 people in the GTA.

So far, swine flu has been confirmed in 31 people in Ontario and all of the cases are reported to be mild.

Dr. Allison McGeer, the director of infection control at Mount Sinai Hospital, says that while both SARS and swine flu cause respiratory illness, fever and cough, the differences between the two viruses outweigh the similarities

For instance, McGeer points out, flu is easily transmitted in public by people who feel only mildly ill.

"SARS on the other hand was not transmitted by people who weren't sick, or not very sick. It was primarily transmitted by very sick people and so that's why we saw most cases in the hospital," she said.

Public health officials predict that a swine flu pandemic could infect one out of every four people. But they also say the vast majority of people who catch it will recover.

The mortality rate for people who contracted SARS approached 10 per cent.

McGeer says the worst flu on record, the Spanish flu pandemic of 1918, was fatal in only two per cent of cases.

"We've had influenza pandemics before. We've been preparing for them for years. And I think the SARS experience in Ontario and Toronto accelerated our efforts at being prepared," said Dr. Vivek Goel, who runs Ontario's agency for health protection and promotion.

Health officials also point out that there are already antiviral medicines to treat swine flu and a vaccine to prevent it could be ready by this fall.

The outbreak of swine flu is being caused by a new strain of a well-known influenza virus and doctors say this crucial difference is why they're confident a vaccine can be developed.