Original Articles By Dr. Lavin Featuring Expert Advice & Information about Pediatric Health Issues that you Care the Most About

The Language of Viral Diseases- What do we mean when we say: a cold, the flu, viral infection, stomach flu?

By Dr. Arthur Lavin

Every winter, when viruses blanket our communities, schools, day care centers, and homes, the words about these illnesses start flying around.

So now and then it may be helpful to pause and think about what all these words and phrases really mean.

Perhaps it would be best to start with the most technical phrases and end with the most used ones.


Underlying all our discussion of all colds and flus is the type of germ that causes every single one of these illnesses, the virus.

If you look at the various categories of living organisms, the great divide is between forms of life that consist of one cell and those that consist of many.  You and I and everyone you know is in the many cell side of that divide.

The many celled forms of life fall into three categories- animals, plants, and mold (single cell forms of fungi are called yeast).

Of these, only molds can cause infections.

The single celled forms of life fall into two categories- yeast and bacteria, both can cause infections.

But then there are viruses.  These very strange items may not even be alive.  They are not cells.  They are, essentially crystals of DNA or RNA coated with proteins.  The proteins unlock living cells to deliver the DNA/RNA, and the DNA/RNA direct the cell to make zillions of copies of their DNA/RNA and protein coat.

So that is the virus.  An entity that appears to go all the way back to the dawn of life, there are, amazingly viruses that only infect the most ancient bacteria.

Viral Infection

A viral infection is a condition in which a virus has landed on you, the DNA/RNA of the virus has successfully invaded your cells, and forced them to make zillions of copies, which in turn, lead to millions of your cells being invaded.

For most viral infections, and certainly the ones we will be talking about, when the virus takes over your cell and makes zillions of new viruses, the cell is utterly and permanently destroyed.

But do not despair, the fact the viruses that cause colds and flus destroy the infected cells is actually good news. Cold and flus all share the fact that the cells destroyed are almost entirely along the lining of the infected area- nose, eyes, lungs, throat, gut.  Once the body destroys all the viruses (by killing all the cells holding the viruses), the body simply regrows new lining, back to good as new.

The more deadly viruses, like HIV that causes AIDS, impairs the cell it invades, but keeps it alive. This leads to the tragic permanent loss of function of the cell, but not to its replacement, that’s how AIDS makes the immune system stop working.

With that in mind, let’s look at the three main viral infections seen every year, mostly in the winter, but actually all year round:

  • Simple respiratory viral infections
  • Respiratory plus blood borne viral infections
  • Viral infections of the gut


Simple respiratory viral infections

The respiratory tract includes any moist lining of the body that touches air (exclusive of the genitals)

Those surfaces include the eyes, nose, pockets of the nose (aka, sinuses and middle ear space), mouth, throat, vocal cord area, and lungs.

When a virus successfully invades (infects) the cells on these linings, they destroy those linings.  To a very large extent, it is accurate to think of a viral infection of a lining as a burn.  In both instances, the area is destroyed and causes tremendous misery until the lining is healed.  In both, the destruction of the lining leads to lots of oozing of fluid- in burns the fluid of the underlying tissues, in the viral case, mucus.

As the lining heals, the cells that kill off the invader gather as do the cells to heal the lining, making for a very goopy scene.

This is why every simple respiratory viral infection starts with clear weeping fluid, and ends with goop.  You can see this in the nose, a  viral infection there starts with clear thin runny fluid, the runny nose, and ends with gross thick yellow and green mucus, the congestion.    That goop does not mean it is a viral infection, all viral infections end with goop.

For all viral infections of a lining, the symptoms are defined by which lining is damaged.  The infection and the damage are the same in any part of the lining, but the symptoms vary.

Viral infection of the nose causes a runny or congested nose.

Viral infection of the sinuses is the cause of the vast volume of mucus and then goop to come out of our little noses. Viral infection of the eye causes a pink eye- redness and fluid and goop.

Viral infection of the throat causes a sore throat.

Viral infection of the vocal cords causes the voice to be altered and if bad enough, barking cough and noisy breathing.

Viral infection of the middle ear space causes earache.

Viral infection of the lungs causes cough.

Any of these lining infections can also cause fever.

All the above can and do happen with simple viral infections of the respiratory linings.

Respiratory plus blood borne viral infections

These infections happen when the virus is able to infect the bloodstream after it destroys the lining.  The influenza virus is very good at this.

When this happens all the above can happen, plus, much higher fevers and much more achiness.  Blood circulation of viruses is also responsible for most rashes during viral infections.

Viral Infections of the Gut

When a virus infects the gut, the same process as in the respiratory system happens, a lining is destroyed.

But as with the above infections, the damage to the lining is the same, but the location of the lining destruction defines just what sort of suffering happens.

Viruses of the gut infect by us swallowing them, so they always land first in the mouth, then stomach, then intestine.

Viral infection of the mouth causes cold sores- a famous example is the mouth part of hand-foot-mouth disease.

Viral infection of the stomach causes vomiting.

Viral infection of the intestine causes diarrhea.

All of these can cause stomach ache and fever.

Species of Viruses

Just like animals come in different species, lions, and tigers, and bears, so do viruses.

The most common species of virus that can attack the respiratory system is the rhinovirus.

Other species that do the same include coronaviruses, adenoviruses, respiratory syncytical viruses (RSV), parainfluenza viruses, and many others.

The most common species of virus that can attack the respiratory system and infect the blood are the influenza viruses.

Any of these viruses can cause the illnesses of the respiratory system listed above.

The most common viruses that infect the gut are the enteroviruses (usually in summer), rotaviruses (usually in February) and noraviruses (year round).

Any viruses can cause a mild 12 hour bug, or lay you low, bedridden and miserable for weeks.

The average length of time of a viral infection is 8 days, and the range can be a few hours to a few weeks.

Most viral infections are contagious for three weeks, so it makes no sense to isolate for the few days of illness, you are contagious for many days once well.


If you have a viral respiratory infection and you and others think it is mild, we say it is a cold.

That’s all that can be said about this widely used phrase.


If you have a viral respiratory infection and you and others think it is severe,  we say it is the flu.

That’s about all that can be said about this widely used phrase.

Notice that the decision of mild or severe is entirely in the mind of the those who are ill or who care about them.

I might have a whopper of a viral infection but think I’m just a little sick, I will say I have a cold.

Or my child may have a very mild viral infection but they seem awfully sick to me, I might say they have the flu.


Notice that none of these words have anything to do with the species of virus.

The species influenza virus can give you a cold OR the flu.  So can any respiratory virus.

So, if you have the flu, you may not be infected with the influenza virus.  And if you are infected with the influenza virus you may have a cold.

A and THE

Notice that colds are always a cold.

Notice that flues are always the flu.

That’s because is a mild word, and the is a more powerful word, that’s the only reason.


If you have a viral infection of your gut, everyone calls it the stomach flu, whether its mild or severe.

Stomach flu is in the gut, flu is in the respiratory system.


  1. We hope this glossary helps clear up all the confusion we have when we hear the words virus, viral infection, cold, flu, stomach flu fly around.
  2.  And we hope the more you know about viruses and the illnesses they cause the more confident you will be caring for your sick child, a challenge we are happy to help with.

To your health,
Dr. Arthur Lavin

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