Health, Health Guide, Physiology Topics, Where Do Viruses Come From

Viruses outbreaks have devastated human populations through history. Viruses have probably been around since the first cells arose, or perhaps even before them. There is disagreement about the origin of the viruses among scientist. As well as there is many theories about the origin of viruses. One of the theories  hypothesis for the origin of viruses, states that some viruses may have evolved from pieces of DNA or RNA that “escaped” from the genome of cells. The escaped DNA could have come from plasmids (pieces of naked DNA that can move between cells) or from transposons (molecules of DNA that replicate and move around the cellular genomes to different positions). Called jumping genes  by Barbara McClintock in the 1950. Another theory is Protobiont Hypothesis: suggests that viruses may have evolved from complex molecules of protein.

Health, Health Guide, Physiology Topics, Where Do Viruses Come From

 

To understand how to deal with epidemics or pandemic and eradicate them, we need first to understand how they spread. The likelihood of a virus (or any pathogen) spreading within a given population is tied to a number of biological traits but it also relates to other variables, including social variables such as the behavior of individuals: how they live, how they crowd in cities or hospitals, and how they travel. Furthermore, requires an integration of ecological, epidemiological, social, cultural, and engineering components.

 

Viruses face a world always changing. Viruses need to be in conditions that are suited toward to the biochemical stability of their virion. Viruses need to be in an environment with the right pH, temperature, and moisture content tolerable to the virus. The environment must also be free of irritants that can destroy the virus. For example, UV radiation, alcohols, and reactive oxygen species can all be harmful to a virus.

 

Viruses cannot replicate outside of the cellular context. They need the cell machinery to make copies of themselves. Viruses can replicate in different tissues and cell types. Viruses are  a liquid poison in the blood. During infection, viruses build complex and specialized intracellular structures associated with membranes taken from the reticulum. Inside these vesicules, viral genomes are transcribed, translated into proteins, and replicated. Viruses don’t breath, eat, produce waste or otherwise. They only need to enter a specific living cell or inject its DNA into a specific living cell to reproduce itself.  

 

Examples of viral pathogens

Disease          

Transmission Route

 Reproductive Numbers R0

EBOV (2014 outbreak)

Body fluids

1.5–2.5

HCV

Blood-to-blood contact

 1.2–1.7

 HIV-1

Sexual contact

 2–5

 IAV H1N1 (1918 pandemic)

Airbone droplet

2–3

Measles

Airbone

12–18

Mumps

Airbone droplet

 4–7

Polio

 Fecal-oral route 

5–7

 Rubella 

Airbone droplet 

5–7

SARS coronavirus 

Airbone droplet

2–5

Smallpox 

Saliva 

6–7

Covid-19

Airbone droplet 

1.5 – 6.49

R0 is an indication of the transmissibility of a virus, representing the average number of new infections generated by an infectious person in a totally naïve population. For R0 > 1, the number infected is likely to increase, and for R0 < 1, transmission is likely to die out.

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