Viruses

Viruses are the smallest of all the microbes, typically between 20-300 nm in size. Viruses can only been seen using electron microscopy. They are also very different to the bacteria and fungi that we have already seen and come in many shapes (see the images below). It is disputed whether viruses are living organisms (alive) at all. This is why we say ‘types’ or ‘variants’ of virus and not ‘species’. Viruses are not made of cells and the structure of virus particles are very simple. Outside the host cell the virus particle is often called a virion.

Videos About Viruses

Viruses are Pathogenic and Parasitic

Viruses are all pathogenic since they cause infectious diseases. They are also parasitic, because they always harm their host cells and are not beneficial at all to their host cells.

There are many infectious diseases in humans that are caused by viruses. Some of them are listed below:

• COVID-19

• Chickenpox & shingles

• Rubella

• Measles

• Mumps

• Colds

• Flu (Influenza)

• Polio (poliomyelitis)

• HPV (Human Papilloma Virus)

• HIV (Human Immunodeficiency Virus)

• SARS (South Asian Respiratory Syndrome)

• MERS (Middle Eastern Respiration Fever)

• Viral meningitis

• Cold sores

• Herpes (herpes simplex)

• Ebola

• Zika

• Hepatitis

• Smallpox

• Rabies

• Dengue fever

• Yellow fever