Who can get infected
by a virus?

When we come to visit someone as guests, we will be welcomed by a kind host.
Do viruses have their hosts? If they do, are the hosts happy with that visit?
Try to find viral hosts!

People

Influenza, Ebola, colds, chickenpox, hepatitis, polio, smallpox ,...
are just some of the examples of diseases in people you are certainly familiar with that are caused by a virus!

Animals

The virus does not circumvent anyone and can infect both invertebrates or vertebrates! Some of the most well-known diseases in animals caused by the virus are foot-and-mouth disease. The disease is widespread in all parts of the world where livestock is raised, with the exception of New Zealand where the virus has never spread!

Dinosaur

Viruses were present on our planet in the ancient past (it is considered that the ancestor of the virus had appeared on Earth about 3 or 4 billion years ago) and have infected the organisms that were then living on Earth. No doubt, dinosaurs were also infected by the virus.

Great-great-grandfather virus?

Viruses are biological entities on the border of the living and non-living world, which is why some scientists consider them to be even the precursors of the entire living world. Has life evolved from these simple forms? Or were viruses created by simplifying complex particles? The debate is still ongoing…

Plants

The first virus detected was one plant virus called TMV, the Tobacco mosaic virus which, as its name implies, infects tobacco, but also other plant species (e.g tomato and pepper).

The most expensive viruses in history

Besides epidemics, the consequences of which have been numerous casualties, viruses have left their mark in human history in other ways as well. Thus, one plant virus, the famous TBV (Tulip breaking virus), caused the financial crisis in the Dutch Republic in the 17th century and introduced the term tulipomania into economic dictionaries. Due to the infection by the famous TBV, the tulip petals had beautiful variegated color patterns to which many Dutch could not resist and were ready to spend incredible amounts of money on these bulbs.

Bacteria

Viruses that infect bacteria are called bacteriophages. Most bacteriophages are found in marine habitats where there are as many as 10 times more of them than their hosts-bacteria!

Amoeba

The first giant virus was precisely discovered in single-celled amoebae. It was a Mimivirus, 400 nm in diameter, and until 2011 was the record holder in terms of microbe size!

Fungus

An interesting example is the CHV1 virus (Cryphonectria hypovirus 1), which infects a fungus named Cryphonectria parasitica. This fungus causes sweet chestnut blight disease - yummy!??? But the fungus infected with the virus multiplies more slowly, which causes the end of the spread of chestnut disease.

Symptoms of sweet chestnut blight disease: a disease caused by a virulent fungus - changes in the color of bark are visible.
The image was kindly provided by doc.dr.sc. Marin Ježić

Viruses infect all forms of life!

The virus cannot replicate outside the living cell. This is the reason why viruses infect so many hosts. Viruses evolve extremely fast. The organisms from the past were also not immune to the infections of the then-existing viruses. The secret of the rapid evolution of the virus lies in numerous mutations that happen during the virus replication. The combination of rapid replication, resulting in numerous offspring, and natural selection has allowed viruses to adapt quickly to different hosts and environmental conditions.

Are viruses specialized?

For example, plant viruses cannot infect other hosts such as humans or animals. How is that possible? It is considered that the evolution of the different groups of viruses occurred independently and that the viruses are highly specialized in infecting a specific cell type to occupy an ecological niche that is not occupied by other pathogenic microbes, thereby, to reducing their competition. For example, plant viruses are specialized in the way they enter host cells passively without using energy through wounds caused previously by mechanical damage. The reason for this is the existence of a cuticle on the surface of the plant or a cell wall on the surface of the plant cells on which there are no receptors to which the plant viruses can bind. As a result of such entry into the cell, plant viruses are not capable of recognizing specific structures on the surface of the cells of animals or humans and bind to them to initiate their entry into the cell.

The viruses that can save us?

More than a hundred years ago, bacteriophages (informally known as phages) - viruses that attack bacteria - were discovered. Their name literally means "bacteria-eater," but they actually multiply within them and destroy them. When they were discovered, it was hoped that they could be used to treat bacterial diseases, but with the discovery of penicillin and other antibiotics, it was forgotten. Considering today's increasing bacterial resistance to antibiotics, it seems like these forgotten heroes could still save us ...