What is a virus?

Mar 2, 2020, 09:51 AM by Dr. Sally Robinson


A virus is a tiny particle that is about one-millionth of an inch long.  Viruses are about a thousand times smaller than bacteria and bacteria are much smaller than most human cells.  A virus particle (virion) consist of the following: nucleic acids which are a set of genetic instructions which can be either DNA or RNA; a coat of protein which surrounds the genetic instructions to protect them and sometimes a lipid membrane which surrounds the protein coat.  Those with a lipid coat are called enveloped viruses as opposed to naked viruses.  Viruses vary widely in their shape and complexity as some can look like a round popcorn ball and others like a spider.

Unlike human cells or bacteria, viruses don’t contain the chemical machinery (enzymes) needed to carry out the chemical reactions for life.  A virus must have a host cell (bacteria, plant or animal) in which to live and to make more viruses.  Viruses are perfect parasites. Once the virus gets into the cell it hijacks the normal cell processes with the viral genetic instructions to start replicating the virus genetic material or making new virions.  The host cell either explodes because of too many virions or runs out of energy.

Above is a simplification of an incredibly complicated variety of viruses and their interaction with a variety of host cells.  Scientists are continually working to understand how these tiny particles get transmitted, reproduce , make the host cell sick, how they infect one host cell and not another and how to prevent and to treat infections.

Right now the world is concerned about the development of a new virus, 2019 Novel Coronavirus.  Human coronaviruses are a family of viruses that commonly cause mild to moderate illness like the common cold.  Almost everyone gets infected with of these viruses at some point in their lives and most of the time the illness lasts for a short amount of time.

An article in by H. Cody Meissner, MD gives some information about this virus.  We know it is contagious and it is being studied to see how easily it spreads from person to person.  Infection can range from mild to severe and the symptoms are similar to other viruses called the “flu”.  The symptoms can be fever, cough, shortness of breath, body aches, sore throat, diarrhea and pneumonia.  As the news will tell you, like “flu”, these infections can result in death.

Currently there is no vaccine to prevent 2019-nCoV infection and the best way to prevent infection is to avoid exposure.  Wash your hand frequently for at least 20 seconds preferably with soap and water. Keep your children away from others who are sick and keep them home if they are ill.  Teach your children to cough and sneeze into their arm or elbow.  Clean surfaces and objects in your home and right now, avoid travel to China.

Up to date information is available at  Stay well.

by Sally Robinson, MD Clinical Professor
Keeping Kids Healthy
Published 2/21/2020

Also See:  UTMB Pediatrics - Pediatric Primary Care
  UTMB After Hours Urgent Care

"2019 Novel Coronavirus", H.Codey Meissner, MD, updated 2/8/2020 (,, viewed Feb. 21,2020.

“Hand Washing: A Powerful Antidote to Illness” by American Academy of Pediatrics, updated 1/28/2020,, viewed Feb 24, 2020.