Giant viruses - Deepstash
The Vast Viral World: What We Know (and Don’t Know) - Issue 99: Universality - Nautilus

The Vast Viral World: What We Know (and Don’t Know) - Issue 99: Universality - Nautilus

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Giant viruses

In 1992, the giant virus, or mimivirus, was first observed during the pneumonia outbreak in England. Later the mamavirus and the even larger pandoravirus stretched the human perception of what it means to be a virus.

Giant viruses are not known to affect human health dramatically. The Asfivirus - the African swine fever virus - transmits from tick to pigs and causes hemorrhagic fever. It is closely related to a giant virus from the sewage in Marseille.

The potential of the electron microscope

The potential of the electron microscope

In 1938, Helmut Ruska, a German physician and biologist, saw the potential of the electron microscope in the application to the field of biology. Helmut collected images, including the variola virus (which causes smallpox) and presented images of the virus particles at a meeting of the Medical Society of Berlin.

Nearly 80 years later, the electron microscope can identify all kinds of pathogens. There are an estimated 1.67 million viral species yet to be discovered.

Why the history of viruses matters

There are three dominant models of viruses that seem to complete each other.

  • The "virus first" model suggests that simple forms of viruses existed before cells and may have provided the raw material for the development of cellular life.
  • "Escape" or progressive model proposes that viruses come from genetic elements that escaped from the genes of larger organisms.
  • The "reduction" model suggests that viruses were once larger, free-living organisms that lost their genetic information and ended up smaller and unable to reproduce except inside the cells of other organisms.

Viruses shape life

  • Viruses exist through symbiosis - an intimate association between two forms of life.
  • Viruses can only reproduce inside living cells where they turn the host's cells into virus-making copying machines.
  • Once the viral information becomes integrated into a host's genome, it becomes part of the host and passes on for generations.
  • In most cases, viruses don't cause disease, and many are beneficial. Viruses can prevent bacteria from invading our gut to cause infections.

The discovery of viruses

Viruses were first named "filterable infectious agents." Experimentation revealed that these minute entities were capable of passing through filters that caught bacteria and other microorganisms.

In the 19th century, Dutch microbiologist and botanist Martinus Beijerinck demonstrated that viruses cause disease in plants. He applied the sap of sickly tobacco plant leaves to the leaves of healthy plants. The healthy plants produced spots on the leaves and malformed.

Viruses and the role of human behavior

In intact ecosystems, like healthy forests, viruses and their wild hosts interact in a delicate balance. But when humans interfere, they can expose themselves to unknown viruses.

When humans modify landscapes, it encourages interactions between people and wildlife and can affect infectious disease emergence. Forest degradation has been associated with outbreaks of viruses that originated in wildlife, such as Nipah, Hendra, and the Ebola virus.

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