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A few nanometre sized virus generally considered non-living was responsible for some of the most catastrophic disasters in human history. Viruses are obligate parasites requiring a host cell to replicate and infect. Diseases such as common cold to AIDS are caused by viral infections. Protections against these threats are through immunity and vaccination. Viruses have characteristic capsid proteins that no other organisms have. Antibodies target these structures to fight viral infections. Although vaccination and improvement of hygiene eliminated otherwise dangerous viruses, virus species evolve rapidly to evade immunity. A new type of virus can emerge with infectivity and lethality to potentially become a pandemic. The following essay will cover 3 different viruses that will pose great threat to human health in future: flu virus, dengue virus and smallpox virus.

Flu virus is an influenza virus that causes yearly flu in humans and other animals. Common symptoms are rapid onset of fever, runny nose, often severe headaches and fatigues. The symptoms are not to be confused with the common cold as rhinovirus is a different virus family. Influenza is a single strand RNA virus with a lipid envelope containing haemagglutinin (HA) and neuraminidase (NA) receptors. Uniquely it has 8 RNA segments allowing effective reassortment of the genome. The HA and NA receptors determine the subtype name of influenza. Currently, H1, H2, H3 and N1, N2 subtypes infect human. Pandemic subtypes include H1N1, H2N2 and H3N2. The H1N1 virus caused the Spanish flu in 1918 and reoccurred in 1977 Russia. The H2N2 and H3N2 subtypes emerged in 1957 and 1968 killing 1million world-wide. Influenza is superb at immune evasion where vaccines only last for 6 mon...

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...s is a large enveloped DNA virus with about 200 genes. It has 4 distinct morphological forms with different number of membranes. IMV (intracellular mature virus) remain in the cell until lysis while IEV (intracellular enveloped virus) with 3 membranes is not infectious. When the virion after exocytosis leaves the cell surface, it is called EEV (extracellular enveloped virus). When the virion is stuck to the cell surface, CEV (cell-associated enveloped virus) produces actin tails from the outer membrane to launch itself to adjacent uninfected cells. Infection through weaponized poxvirus with high titre, aerosol transmission and high mortality rates will be devastating. Although there is a vaccine, many will not be vaccinated as poxvirus is eradicated in nature. Mass production of vaccines in a short period of time will be impossible and casualties will be massive.

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