Emerging Viruses

First off, what is an emerging virus?? Well, its an known virus, that is thought to infect animals only, but is showing an increasing incidence in humans. Sounds familiar?? If you guessed bird flu or SARS, you're right. 

Now, how does a virus that infects animals only start infecting humans?? There are various factors, which can be lumped into 2 groups: Virus and Human factors.

Virus Factors:
(i) Spontaneous Evolution
Alright, now, viral populations are hetergenous and there IS a limit of variation, but that is a really big number. Furthermore, as there is selection pressure present, this results in high mutation rates, and thus, spontaneous evolution, where a new virus entity is formed.

(ii)Random Assortment, or the generation of a new strain due to the co-infection of different strains in an individual. That was long, so I'll be using Random Assortment instead.

As previously stated, in the life cycle of a virus, the genetic material of the virus undergoes replication and expression. However, when two viruses infect one cell at the same time, or co-infection, the host cell gets mixed up during the assembly stage and a "new" vius is produced and released out of the cell to infect others. Thus RANDOM assortment

Human factors:

(I)Man invading the natural habitat of animals. Truly, this shows why humans, at times, should not destroy Mother Nature. Though other times, we humans, too have no other alternative. Anyway, on with the explanation.

Examples of humans invading the animals' natural habitat would be deforestation, which puts man closer to wild animals. 

(II)Climate change is an important factor, especially with global warming nowadays. 

This increase of global temperature will definitely affect the ecosystem on a whole. Insects, especially, are greatly involved as warmer temperatures have been linked to an increase in reproduction of mosquito, a vector of the virus which causes dengue fever. Hence, increase in temperature = increase in viral vectors = more people infected.

(III)Breakdown in Public Health

Though this might not happen in developed countries, it still happens in less developed countries. Unhygenic surroundings increase the likelihood of incidence. 

(IV)Concentration of people with shared lifestyle

As the concentration of peopple increase, so does the chances of contracting a virus from an infected person. So, when one person is infected, that one person can spread to another 2 people who then infect others, continuously infecting other, increasing incidence.

As seen above, some factors are caused by humanity, others by nature. From this, I realised that the cause of increasing incidence has so many factors, and mostly are results of our own actions.