Avian flu (highly pathologic avian influenza) is the name given to a strain of flu that mainly circulates in Asia impacting various bird species with limited transmission to humans. Swine flu on the other hand, is the name given to a strain of influenza that emerged from South America–Mexico–in late 2008. This strain of influenza was particularly troublesome because it seemed to impact otherwise healthy people in a very dramatic way. And lastly, the term pandemic. A pandemic has been seen by the media as a term that indicates large numbers of deaths from disease. Although throughout history this is often the case, a pandemic is not an automatic term for mass fatalities. The term pandemic simply means the disease has spread around the globe and impacted many areas of population.
types of influenza viruses and influenza virus belongs to the category of diseases known as Orthomyxoviruses. The three types of flu are Type A, Type B, and Type C. Type A influenza is known as a multi-host pathogen infecting both humans, swine, and birds. This is the most virulent group and is classified by its surface antigens into subtypes. It is these subtypes that make up the H and N that we hear so much about on the news. H stands for hemagglutinin and N indicates neurominidase. Both of these are surface proteins on the virus that allow the virus to get into a host cell, reproduce, and then escape. Remember, viruses are parasites and need to have a host to survive. There are 15 different types of H's and nine types of N's giving us a total of 135 potential combinations of type A influenza. Type B influenza is seen mostly in humans and although it's very common it is much less severe than Type A influenza. Epidemics involving type B influenza occur much less often than those involving Type A. It's important to note here that human seasonal flu vaccine includes two strains of Type a and one strain of Type B protection. Given that there are 135 potential type a influenza combinations and only two are included in the seasonal flu vaccine, indicates why we have years when the seasonal flu vaccine is less effective than others… that is, scientists have to guess which two strains of influenza should be included in the vaccine. Type C influenza infects humans and swine and has a completely different pattern of surface proteins. Normally Type C presents with rare occurrences and has mild or no symptoms. In fact, by age 15 most people have antibodies against Type C influenza.