Viruses are not living organisms. On their own, they are capable of nothing until they enter a living cell. Without cells, viruses would not be able to multiply.

Viruses are even smaller than bacteria, and their DNA is protected by a protein coat. The DNA contained in the virus moves inside a living host cell. This causes the cell to make a copy of the virus DNA, producing more viruses. The multiplied viruses are released from the host cell, with the host cell often dying as a result.

Diseases caused by viruses are often troublesome, because the viruses are protected within host cells. Antibiotics have no effect on viruses at all.

The image on the right displays the basic structure of a virus. It is so simple that viruses are not even classified as living organisms. They are always parasitic and need a host to survive. The numbers show various structural features of viruses: 1. surface protein (this allows the virus to recognize its host cell), 2. envelope (derived from the host cell), 3. coat (protein), 4. genetic material.

 

GLOBALLY SIGNIFICANT VIRAL DISEASES

Name of the virus	When and where?
SARS (Severe Acute Respiratory Syndrome, coronavirus)	A virus that spread across Asia during the year 2003. Approximately 8 000 people were infected, with just under one thousand fatalities. Wikipedia
Ebola	An epidemic that affected Africa between the years 2014 and 2016. Approximately 30 000 people were infected, with approximately 13 000 fatalities. Wikipedia.
Zika	A virus spread by mosquitoes in South America between the years 2014 and 2016. Millions of people were infected, with no confirmed fatalities. Wikipedia
Coronavirus (COVID-19)	Originated in China and spread into a global pandemic in 2019-2020. Wikipedia.