When the last millennium came to an end, the Y2K bug was grabbing attention. As the first decade of this one neared an end, a pandemic bug was in the spotlight.

In the past 10 years, fear has accompanied new viruses, including bird flu, or H5N1, severe acute respiratory syndrome, or SARS, and most recently, the virus formally known as 2009 pandemic influenza A, or H1N1.

But much can be learned from the decade's experience with these viruses, experts say.

For public health officials, the challenge in a pandemic is to inform people about how they can protect themselves without causing panic.

Worldwide, governments set up their pandemic plans based on bird flu, a highly pathogenic virus that infected a relatively small number of people, mainly in China and Southeast Asia, where it has had a case-fatality rate of about 60 per cent. Evan Frustaglio, a 13-year-old hockey player from Toronto, died on the eve of the H1N1 vaccine becoming available. Demand for the vaccine jumped overnight. (Facebook)

The worst-case scenario is a virus that is both highly pathogenic and highly transmissible, meaning it causes serious disease and spreads easily from person to person.

While both bird flu and SARS were highly pathogenic, neither was particularly transmissible. The opposite is the case with H1N1, which is very transmissible but is not very pathogenic, said Sir Roy Anderson, a professor of infectious disease epidemiology at Imperial College in London.

When H1N1 first emerged in Mexico in April 2009, the fatality rate seemed about one in 100, but this turned out to be too high, since only the serious cases came to the attention of health authorities. The death rate is now estimated to be about one in many tens of thousands or perhaps one in a 100,000 — in the same ballpark as typical seasonal flu.

"At the start, the media messages were on average balanced but a little bit alarmist because everybody thought this was the big one, with a totally novel strain of the virus with a high case fatality," Anderson said.

By early fall, the news media started reporting on a much smaller fraction of people sickened with serious illness from H1N1.

Another reason the case fatality rates were overestimated for H1N1, Anderson said, is that it is a difficult disease to diagnose. Influenza causes similar symptoms to cold virus, including chest secretions and a rapid rise in temperature.

Problems in diagnosing H1N1 show the need for more sophisticated ways of telling if someone has been exposed, he said.

The H1N1 flu pandemic also taught the importance of monitoring flu viruses for mutations that occur when someone is infected with two viruses at the same time and the viral genetic codes get jumbled.

Panic from pandemic alert?

That's how bird flu could become more transmissible or swine flu could become more pathogenic — changes scientists worldwide are watching for closely. They are also looking for any evidence that flu viruses are becoming resistant to antiviral medications such as Tamiflu and Relenza.

When the World Health Organization raised its alert level for H1N1 from three to four, then to five and finally six — a full-blown pandemic that is widespread geographically — the changes were meant to signal to governments to put their pandemic plans into place, not to cause panic in the public.

When the public is told to "be vigilant" during an alert for example, governments need to put out accurate, balanced views of what's happened and be frank if there's uncertainty, Anderson said. The design of protective masks to protect health-care workers improved after the SARS outbreak in 2003 that killed 800 people around the world, including 44 in Toronto. (Kevin Frayer, Canadian Press Picture Archive)

"Sometimes [alerts] help, sometimes they induce panic," said Clive Seale, a professor of medical sociology at Queen Mary, University of London, who edited a book titled Health and the Media.

Those now-familiar steps — washing your hands, avoiding touching your face, coughing and sneezing into your sleeve, reducing mixing, staying home when sick, early treatment with antivirals, and getting vaccinated — probably did make a difference in stemming the spread of H1N1.

But researchers won't be able to tell until next year, when they're able to analyze the pattern of the pandemic, as they do with seasonal flu outbreaks.

Attention to details

Health Minister Leona Aglukkaq made the same point during her year-end news conference on H1N1. She said it was important to deal with facts of confirmed cases when the virus emerged during the spring of 2009. Doing otherwise could have diverted resources to where they weren't needed, she said.

Canada's pandemic plan clearly outlined the roles and responsibilities for each jurisdiction, applying one of the lessons learned from SARS, Aglukkaq said.More outbreaks of infectious diseases such as H5N1 bird flu may occur as livestock continue to be brought into densely populated cities. (AP Photo)

But after governments started drafting pandemic plans in response to bird flu, in Anderson's view, they focused on generalities without paying enough attention to logistics and details.

Details such as how to get antiviral drugs to people within 48 hours of infection, deciding on who should be in priority groups for the vaccine, and how to get the vaccine into arms are all important steps that governments should work out in advance, rather than during a pandemic, Anderson said.

SARS also highlighted to hospitals why it's so important to focus on infection-control procedures, since the infection persisted for a long period and caused serious illness for nurses and doctors working in the institutions. The outbreak also led to the development of new facemasks that were more effective and easier to breathe in, Anderson said.

More outbreaks are "somewhat inevitable," he said, given that the world's population continues to grow and live in densely populated cities. To serve these urban residents, livestock are brought into cities, where infections are likely to spread from animals to humans in the future.

The reality of today's world means that when new viruses emerge, air travel largely dictates its spread early on in the outbreak. In the cases of both severe acute respiratory syndrome in 2003 and H1N1 in 2009, air travellers spread the infection from its origin to major cities around the world.