Influenza A and influenza B are 2 of the 3 types of influenza viruses associated with annual outbreaks and epidemics of influenza. The third type, influenza C, causes only mild disease and has not been associated with widespread epidemics or pandemics. Annual outbreaks of influenza are due to minor changes in the surface proteins of the viruses that enable the viruses to evade the immunity humans have developed after previous infections with the viruses or in response to vaccinations.
Only influenza A virus can cause pandemics. When a major change in either 1 or both of their surface proteins occurs spontaneously, no one will have partial or full immunity against infection because it is a completely new virus.Here is how we gain immunity to some diseases. This happens because we acquire antibodies directly from our mother when we are in her womb.Continue reading this on how we gain immunity all our lives. As our body is exposed to new organisms we start to gain some specific immunity. When infections occur they create memory cells. This helps to protect us from any future infections from a related or the same organism. If this new virus also has the capacity to spread from person-to-person, then a pandemic is most likely to occur.
Consequences Of An Influenza Pandemic
During the last century, 3 influenza pandemics caused millions of death worldwide, social disruption and profound economic losses. Influenza experts agree that another pandemic is likely to happen. Epidemiological models project that in industrialized countries alone, the next pandemic is likely to result in 57-132 million outpatient visits and 1.0-2.3 million hospitalizations, and 280 000-650 000 deaths over less than 2 years. The impact of the next pandemic is likely to be greatest in developing countries where health care resources are strained and the general population is weakened by poor health and nutrition.