Epidemics and Pandemics

What is an epidemic?

An epidemic is an outbreak of disease that spreads within a specific region and/or country.

What is a pandemic?

A pandemic is a sudden, widespread outbreak of a new strain of the influenza virus, that has significant morbidity and mortality and is easily transferred between humans.

Topics

Risk of an Influenza Pandemic

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What is Pandemic Influenza?

While some 1500 deaths occur annually in Canada due to influenza infection, for the majority of people, influenza remains an uncomfortable, but not life-threatening, experience, associated with winter.

However, three to four times a century, a radical change will occur in the genetic material of the influenza A virus and a new subtype of the virus will suddenly appear. Because it is a radically different strain, the protection that people have developed to the influenza that occurs every year will not apply. Everyone is susceptible to infection with the new strain, and will be at greater risk of developing the severe complications of influenza infection, like pneumonia. In such a situation, the virus will spread rapidly around the world, and a global epidemic, called a pandemic, will result.

In the 20th century, there were three pandemics, in 1918-1919, 1957-1958 and 1968-1969. Pandemics are unpredictable in their timing.

In May 2009, the World Health Organization (WHO) declared a pandemic of H1N1 influenza (human swine flu). This influenza is not the same as seasonal influenza, though its symptoms are similar. It therefore requires a separate vaccine which should be available in late fall 2009. To learn more about the risks and differences between the two types of influenza, speak to your healthcare provider or visit the Public Health Agency's website, www.fightflu.ca .

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How severe was the 1918-1919 influenza pandemic?

Known as "Spanish Flu", the influenza pandemic of 1918-1919 was a global disaster, killing more people than World War I. Somewhere between 20 and 50 million people died. It has been cited as the most devastating epidemic in recorded world history. More people died of influenza in a single year than in four years of the Black Death Bubonic Plague from 1347 to 1351.

Few people alive today remember the Spanish flu firsthand. But the global epidemic lives vividly in the collective memory of medicine and public health. We are also reminded of the Spanish flu pandemic in 2003 with the outbreak of SARS (severe acute respiratory syndrome) which was considered a deadly pandemic threat. Click here to read an interesting Washington Post article on SARS and how it relates to the Spanish flu pandemic.

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Influenza pandemic patterns

This expectation is based on the historical patterns of the disease. The average time elapsed between each of the last four pandemics has been 25 years; however, the range has varied between 11 and 39 years, with the most recent pandemics occurring in 1968, 1957, 1918.

What can we do to prevent a pandemic from occurring?

With our current scientific knowledge, there is no way to prevent a pandemic from occurring. But there are ways to lessen the impact that a pandemic would have, specifically to decrease the number of deaths, and control its impact on health care resources.

A global network of laboratories and surveillance systems coordinated by the World Health Organization keeps a watchful eye for new influenza strains.

Reference: www.phac-aspc.gc.ca/influenza/pandemic_e.html

Situation in Canada

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In Canada statistically, a usual influenza season is unlikely to cause death in young, healthy individuals. Yet it's the leading infectious cause of hospitalization and death in Canada. The reason is it attacks and weakens the elderly and the ill, i.e. people with heart and lung conditions, diabetes, kidney disease, HIV and cancer.

Conservative estimates place the yearly number of Canadian deaths from influenza at 1,500 while some experts say it will kill about 4,500 Canadians this year. That number can climb up to 6,000 if you include those who will die from complications, such as pneumonia.

What would happen in Canada during a pandemic?

Based on our knowledge of the two most recent pandemics, experts believe that pandemic influenza virus could reach Canada within 3 months of being detected anywhere in the world, and would have its maximum effect on the Canadian population within 5-7 months. Using information from the last three pandemics and a disease model developed by the U.S. Centers for Disease Control and Prevention, Health Canada estimates a pandemic could potentially result in between 9000 and 51,000 deaths in Canada if a vaccine was not available. A severe shortage of hospital beds could also occur.

What can be done in Canada to prevent a pandemic from occurring?

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When the pandemic strain emerges, international surveillance will provide Canada with an early warning, in order for us to start vaccine production as quickly as possible.

Immunization will be the only way to minimize the impact of the pandemic on Canadians.

Health Canada continues to work with provincial and territorial governments to finalize a contingency plan which would provide the basis for coordinated and collaborative action by the provinces, Health Canada and other federal agencies in the event of a pandemic.

In 2001, Health Canada finalized a pandemic vaccine contract which will enable vaccine to be made available to all Canadians at the time of a pandemic.
Reference: www.phac-aspc.gc.ca/influenza/pandemic_e.html

History

Chronology:

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400 B.C.:
Hippocrates records an outbreak of a cough, followed by pneumonia and other symptoms, at Perinthus in northern Greece (now part of Turkey). Several possible identifications have been suggested, including influenza, whooping cough and diphtheria.

 

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212 BCE
The historian Livy describes an infectious disease, perhaps influenza, which strikes the Roman army.

1781-'82
Considered among the greatest manifestations of disease in history, this influenza pandemic afflicts two-thirds of the people of Rome and three-quarters of the population of Britain. Influenza also spreads widely in North America, the West Indies and Spanish America.

 

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1789
A widespread epidemic of influenza hits New England, New York and Nova Scotia in the fall. Most deaths appear to come from secondary pneumonia.

1829-'32, 1836-'37
An epidemic begins in Asia late in 1829. From there it spreads to Indonesia by January 1831. The disease also breaks out in Russia in the winter of 1830-'31 and spreads westward. By November it reaches the United States.

 

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1889-'90
Named the Russian flu, this worldwide influenza epidemic, the most devastating up to that time, begins in Central Asia in the summer of 1889, spreads north into Russia, east to China and west to Europe. It eventually strikes North America, parts of Africa and major Pacific Rim countries. By conservative estimates, 250,000 die in Europe, and the world death total is two to three times that.

1917-'19
The Spanish flu, the most lethal influenza pandemic ever, kills more than 20 million people. More people die as a result of this flu than die during World War I. Its spread is facilitated by troop movements in the closing months of the war. Mortality rates are unusually high for influenza, especially among young, otherwise healthy adults.
For more on the Spanish flu, see "How severe was the 1918-1919 influenza pandemic?" in the "Influenza Epidemics and Pandemics" section above.

image of woman mourning

1957-'58
The Asian flu starts in southwest China in February 1957, possibly having originated in 1956 in Vladivostok, Russia, then spreads throughout the Pacific. Globally it affects 10 percent to 35 percent of the population, but overall mortality is much lower than in the 1918 epidemic.

1968-'69
Hong Kong flu claims 700,000 lives worldwide, 34,000 in the United States.

1976
"Swine flu" outbreak, [influenza A(H1N1)]. A new swine flu virus infects soldiers at Fort Dix, New Jersey in 1976, and influenza experts warn that a major pandemic could occur if the virus spreads. The virus does not spread, and a pandemic never begins, but more than 40 million Americans were vaccinated.

1997
"Avian flu" outbreak, [influenza A(H5N1)]. In 1997, 18 people in Hong Kong are hospitalized because of infection with a new type of virus that was previously seen only in birds. Six of those people die, and officials in Hong Kong order the slaughter of all chickens in the area, as chickens were widely infected by the virus. Studies found that this H5N1 influenza spread from poultry to people but not easily from person to person. No new human infections with H5N1 have been found since the chickens were slaughtered. Hong Kong officials continue to look for new cases.

1999
[influenza A(H9N2)] infections in Hong Kong. The Hong Kong Department of Health isolates influenza A viruses from two children (1 and 4 years of age) and send the viruses to the National Institute for Medical Research, London and the Centers for Disease Control and Prevention, Atlanta. In April 1999, both laboratories identify the viruses as influenza A(H9N2). These were the first confirmed human infections with influenza A(H9N2) viruses. Influenza A(H9N2) usually infects birds. It is not known how the two children in Hong Kong became infected with influenza A(H9N2). Both children were hospitalized but recovered fully. Other human H9N2 infections were reported from China but no new infections have been reported since April 1999.

August, 2002
An influenza epidemic in Madagascar (an island country located in the Indian Ocean, off the eastern coast of the continent of Africa) takes the lives of some 400 people in three weeks, with over 5,600 others infected. The hardest hit provinces in the country--one of the poorest in the world--are Fianarantsoa in the south and Toamasina on the east coast of the island. Testing has confirmed that the strain involved in the epidemic is type A influenza. The World Health Organization sent an international team of experts to help tackle the epidemic.

In the News:

BBC News

Reference: http://www.msnbc.msn.com/id/7488810/