Flu Facts
Seasonal Influenza, is a viral infection that attacks the respiratory tract including the nose, throat and occasionally the lungs. The infection, which usually lasts about a week and is highly contagious, is characterized by fever, headache, muscle aches, cough and sore throat.
Each year epidemic (seasonal) influenza infects between three million and five million people worldwide and results in 250,000 to 500,000 deaths. Most of these deaths are associated with complications from pneumonia. The elderly are the most vulnerable.
H1N1 "Swine" flu, 2009 H1N1 influenza virus was detected in people in Mexico, United States and Canada in April 2009. This virus is spreading from person to person worldwide, probably in much the same way that regular seasonal influnenza viruses spread. On June 11, 2009 the World Health Organization (WHO) declared that a pandemic of 2009 H1N1 influenza was underway.
This virus was originally referred to as "swine flu" because laboratory testing showed that many of the genes in the virus were very similar to influenza viruses that normally occur in pigs (swine) in North America. But further study has shown that the 2009 H1N1 is very different from what normally circulates in pigs in Europe and Asia and bird (avian) genes and human genes. Scientists call this a "quadruple reassortant" virus.
H5N1 "Avian" flu, is a virus that normally affects only birds. However, sometimes influenza viruses that infect animals may adapt to infect people. In 1997, the first case of H5N1 avian influenza to infect humans was documented in Hong Kong. Since then, the H5N1 virus has spread across Asia, has mutated and has infected hundreds of people, killing approximately half of those infected. Avian influenza in humans is characterized by an unusually high mortality rate, including otherwise healthy people of all ages, and is believed to have pandemic potential.
The H5N1 avian influenza virus is rapidly evolving into antigenically distinct clades, or families. H5N1 clade 1 flu viruses were identified in Vietnam in 2003; by 2005 a second clade was identified in Indonesia. Novavax scientists have succeeded in making a vaccine candidate designed to protect against the H5N1 clade 2 influenza virus.
| Recent Avian Influenza Strains That Have Infected Humans | |
| H5N1 | Identified in 1997 in Hong Kong, since detected in Cambodia, China, Indonesia, Thailand and Vietnam |
| H7N7 | Identified in 2003 in the Netherlands |
| H9N2 | Identified in 1999 in Hong Kong |
| H7N3 | Identified in 2004 in Canada |
Influenza pandemics are rare but typically recur every 10 to 50 years. A pandemic occurs when:
- A novel subtype of influenza infects humans who are immunologically naïve to the virus
- The virus causes severe mortality in humans; and
- The virus spreads efficiently from human to human
| Influenza Pandemics of the 20th Century | |
| 1918 | The Spanish flu caused approximately 40 million deaths |
| 1957 | The Asian flu caused approximately 2 million deaths |
| 1968 | The Hong Kong flu caused approximately 1 million deaths |
| 2009 | The Swine flu caused approximately 16,460 deaths and infected about 55 million people between April 2009 through to December 12, 2009, according to the Centers for Disease Control and Prevention (CDC). |