# 4143
Every time a hurricane approaches the coastline, the weather bureau warns residents not to be fooled by a lull in the storm caused by the eye passing overhead. The storm winds could return from the opposite direction as fiercely as before.
While pandemics don’t have a calm eye like hurricanes, they do tend to come in waves. And the lull in between waves can lead some to believe the pandemic is over when it isn’t.
In 1918 there were two deep lulls between the three pandemic waves. And in the decade that was to follow, there were repeated flare ups of virulent influenza.
The graph below comes from:
REVIEW AND STUDY OF ILLNESS AND MEDICAL CARE WITH SPECIAL REFERENCE TO LONG-TIME TRENDS
Public Health Monograph No. 48, 1957 (Public Health Service Publication No. 544)
And it shows the spikes of influenza in the United States in the decade following the 1918 pandemic. Similar reports came from around the world.
And in 1957, the Asian Flu pandemic seemed to disappear completely for more than a year, only to return in 1959 and again after a two year lull during the 1962-63 flu season.
When a sufficient percentage of the population develops (herd) immunity (or a virus mutates to something less `fit’), a pandemic winds down.
Case levels drop below the epidemic threshold, and the pandemic is declared to be `over’.
Viruses are notoriously unstable, and mutate constantly, and can learn to evade acquired immunity. Even years after a pandemic is over, the responsible virus can flare up in some localities, and cause significant morbidity and mortality.
The recent drop in reported infections here in the US and in Canada has led many to believe the pandemic of 2009 is almost over. That there is no longer a need to get vaccinated.
Maybe we get lucky, and the worst is over. Hopefully that’s true. But history tells us, you have to look back from a distance to know when a pandemic really ended.
This reminder from Canada’s chief public health officer, Dr. David Butler-Jones.
Top doc: Flu threat not over
By CHRISTINA SPENCER, NATIONAL BUREAU
Last Updated: 10th December 2009, 5:13am
OTTAWA -- Critics are off-base to suggest the worst of the H1N1 pandemic is over or that vaccination is no longer needed, Canada's chief public health officer says.
Between 30% and 40% of Canadians have been immunized for H1N1, Dr. David Butler-Jones told reporters yesterday, but he still wants millions more to get the shot.
"Unfortunately, there are Canadians who are denying themselves the benefits of immunization because they believe that we've reached a critical mass of our population with immunity," he said.
"I question that logic. The whole point of medical and public health efforts is to improve health and reduce illness and suffering."
TV CAMPAIGN
The Public Health Agency of Canada plans a TV campaign to convince Canadians they should still get the shot. Despite statistics showing a continued slowdown in flu activity in Canada, Butler-Jones said it would be "imprudent to declare a peak."
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