When we Consider about Ecology of Poliovirus, the (+) ssRNA genome of poliovirus, a single long RNA molecule, is unable to recombine with (+) ssRNA genomes from other related picornaviruses by the process of crossing-over. Crossing over requires a set of highly specialized enzymes that are not available to the viruses. This means that there are only a very small number of closely related poliovirus strains and immunity against one of these strains confers immunity against the others. Influenza virus presents a dramatically contrasting example. Influenza virus genome is composed of different RNAs, each carrying different genes
There are two different types of flu virus simultaneously infect a single host cell, two viral genomes may recombine by simply exchanging RNAs. Progeny virion released from this cell can have RNAs from each different infecting virus and thus a new and unique strain has been created. This is devastating consequences on human health
Natural reservoir for many flu viruses is the shore bird population around the world, which includes migratory ducks and geese. At least a dozen distinct strains of flu virus live continually in these birds. In rural China and other parts of the world, ducks and pigs are kept in close proximity with one another and with humans. Ducks become infected with a flu virus originating in the wild shore birds. They can then pass the virus to a pig, which is also readily infected by human flu viruses. In the infected cells of the pig, the two viral genomes can mix and RNAs from both viruses can be packaged into one virion. In this way, a new recombinant flu virus, one quite different from pre existing strains may emerge and infect humans
Exposed humans would have not experienced this strain before, and thus there is no immunity to it. Flu virus now spreads throughout the population creating a worldwide epidemic. These pandemics create serious respiratory infections, but usually prove lethal to only a few, mostly the weak and elderly
There are two different types of flu virus simultaneously infect a single host cell, two viral genomes may recombine by simply exchanging RNAs. Progeny virion released from this cell can have RNAs from each different infecting virus and thus a new and unique strain has been created. This is devastating consequences on human health
Natural reservoir for many flu viruses is the shore bird population around the world, which includes migratory ducks and geese. At least a dozen distinct strains of flu virus live continually in these birds. In rural China and other parts of the world, ducks and pigs are kept in close proximity with one another and with humans. Ducks become infected with a flu virus originating in the wild shore birds. They can then pass the virus to a pig, which is also readily infected by human flu viruses. In the infected cells of the pig, the two viral genomes can mix and RNAs from both viruses can be packaged into one virion. In this way, a new recombinant flu virus, one quite different from pre existing strains may emerge and infect humans
Exposed humans would have not experienced this strain before, and thus there is no immunity to it. Flu virus now spreads throughout the population creating a worldwide epidemic. These pandemics create serious respiratory infections, but usually prove lethal to only a few, mostly the weak and elderly
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