What is Pandemic Influenza?
Pandemic influenza is a global outbreak caused by a new influenza virus. This new virus spreads easily from person to person, causing serious illness and death. People do not have defenses (immunity) against the new virus because it has never before infected humans, so many people are at risk. Historically, pandemic influenza has caused widespread disruption of everyday life, and many deaths.
Influenza, or flu, is a viral infection of the lungs. There are two main types of flu virus, A and B. Each type includes many different strains and new strains emerge periodically. Flu outbreaks occur most often in late fall and winter. Pandemic flu is a global outbreak of disease that occurs when a new influenza A virus appears in humans, causes serious illness and then spreads easily from person to person worldwide. What’s the difference between a pandemic and a seasonal outbreak of flu? A pandemic is caused by a new influenza A virus that most people have never been exposed to, so everyone is susceptible. Pandemic strains also often cause more serious disease. Because of this, past flu pandemics have led to high levels of illness, death, social disruption and economic loss. Seasonal outbreaks of flu are caused by strains of flu virus similar to those of past years. Some people may have built up immunity, and there is also a vaccine for each year’s flu season.
Three or four times a century, a radical change occurs in the genetic make-up of the influenza A virus and a new strain of the virus, suddenly appears. As a result, the protection and immunity that people have developed against influenza may not protect them from this new strain. When this happens, everyone would be susceptible to infection and would be at greater risk of developing severe complications like pneumonia. The virus may even spread rapidly around the world, causing an influenza pandemic. The frequency of pandemics is unpredictable, but most experts agree that another one is likely to occur within the next 5 to 10 years. This is based on the historical patterns of pandemics – the average time elapsed between each of the last four pandemics was 25 years. It has been over 30 years since the last pandemic.
