|
| Aspect |
Before A/H1N1 |
Since A/H1N1 |
| One line summary |
WHO 2003-9: "An influenza pandemic occurs when a new influenza virus appears against which the human population has no immunity, resulting in epidemics worldwide with enormous numbers of deaths and illness"10 |
WHO: "An influenza pandemic may occur when a new influenza virus appears against which the human population has no immunity"10 |
| Virus and immunity |
WHO 2005:"Most people will have no immunity to the pandemic virus"1
|
WHO: "The vulnerability of a population to a pandemic virus is related in part to the level of pre-existing immunity to the virus"12
|
| US CDC 1997: "When antigenic shift occurs, the population does not have antibody protection against the virus"13 |
US CDC: "Cross-reactive antibody [to A/H1N1] was detected in 6%-9% of those aged 18-64 years and in 33% of those aged >60 years"5 |
| Impact (health, social, economic) |
WHO 2005: "Large numbers of deaths will occur . . . WHO has used a relatively conservative estimate—from 2 million to 7.4 million deaths . . .
Economic and social disruption will be great"1 |
WHO: "H5N1 has conditioned the public to equate an influenza pandemic with very severe disease and high mortality. Such a disease pattern is by no means inevitable during a pandemic. On the contrary, it is exceptional"14 |
CDC 1997: "The hallmark of pandemic influenza is excess mortality"13
|
CDC: "There are some pandemics that look very much like a bad flu season"8 |
| Canada 2006: "An influenza pandemic results if many people around the world become ill and die from such a [new form of influenza] virus"15 |
Canada: "An influenza pandemic does not necessarily cause more severe illness than seasonal influenza"9 |
