Virus vs. Bacteria



Have you ever been really really worried that your kid had a serious illness only to take them to see the doctor and be told they had “just a virus”?  Have you ever taken your kid in for a well visit only to be told they had an ear infection and needed an antibiotic?  And you were left thinking, “but he doesn’t even seem that sick”?  I try very hard never to use the phrase “just a virus” because this implies that your child isn’t really sick.  Your kid has a significant fever and feels like death warmed over and some smug physician is telling you your kid isn’t that sick and you’re just being one of those crazy anxious parents.  It’s “just a virus”, settle down.  Why are you even here?

I would say the most confusing thing about childhood illness for most parents is the difference between a virus and a bacterial illness.  Here’s the take-home point I want everyone to hear – it’s not that viruses can’t cause serious illness, it’s that I cannot kill a virus.  I have no medication to combat them.  Most of the time that’s OK, even though your kid looks like crap on a cracker and feels truly horrible.  The good news is that your child’s immune system CAN defeat most viral infections while parents and physicians alike take on an observer’s role.  Before I dig into this topic I want y’all to understand that this post is not intended to keep people out of my office.  If you’re worried or you don’t know what to do, come see me.  That’s my JOB.  This post is to inform worried parents so that when I tell them their kid has a viral illness, they will understand exactly what that means and what they need to do.  I want them to understand that the words “your child has a viral illness” do not translate to “your child is fine, he’s not sick, go away” but rather translate to “I get that your child is miserable and I hate that, but I cannot cure this, it has to run its course, but your kid is going to be just fine”.

Let’s start with some definitions:


  1. an ultramicroscopic (20 to 300 nm in diameter), metabolically inert, infectious agent that replicates only within the cells of living hosts, mainly bacteria, plants, and animals: composed of an RNA or DNA core, a protein coat, and, in more complex types, a surrounding envelope.
  2. Informal. viral disease.
  3. a corrupting influence on morals or the intellect; poison.



  1. ubiquitous one-celled organisms, spherical, spiral, or rod-shaped and appearing singly or in chains, comprising the Schizomycota, a phylum of the kingdom Monera (in some classification systems the plant class Schizomycetes), various species of which are involved in fermentation, putrefaction, infectious diseases, or nitrogen fixation.


Clear as mud, right?  Here’s the simplified version – bacteria are alive.  They are living cells that have to take in nutrients and replicate themselves.  Because they are alive, I can kill them.  I can disrupt their cellular processes.  I can interfere with their processes of feeding or repairing themselves, I can interfere with their reproductive processes.  Furthermore, their structures and processes are DIFFERENT from human cell structures and processes so not only can I kill them, I can kill them without killing off the patient’s own cells.  Honestly (getting really really real here, peeps), I kind of like finding a bacterial illness.  You know why?  Because I can treat that.  I can give your kid a medication that will make them feel better very quickly and that makes me feel good about myself.

We are not sure that viruses are alive.  They are basically just packets of DNA (or RNA) in a protein capsule.  They don’t have a cell membrane.  They don’t have organelles.  They don’t need to take in nutrition.  They reproduce by hijacking your body’s cells, replacing their DNA, and using the host cell’s structures to manufacture new virus particles.  In order to “kill” a virus, I’d have to kill the host cell.  I don’t have a way to differentiate between virus-infected cells and normal cells (although your immune system can).  Thus, we have very few anti-viral drugs and even the ones we have are only moderately effective.

It’s not that bacterial illnesses are serious and viral illnesses are no big deal.  Some viral illnesses can be life-threatening.  Some bacterial illness will resolve on their own with no intervention.  Bacterial illnesses can be treated with medications while viral illnesses cannot.  There are people out there in internet world who would like to convince you that their all-natural, magical remedies can treat your viral infection but they’re lying to you.  Your viral illness will likely resolve on its own.  Various natural remedies may be effective in managing the symptoms and making you feel better but NOTHING gets rid of the virus any faster than your good old immune system would have done on its own.  Let’s talk about some examples.

Viruses that will make you miserable but are not serious (i.e. they will resolve without medicine and they are not going to kill you, even though you may feel like death):

  • The common cold (rhinovirus, coronavirus)
  • Coxsackie virus (hand food mouth disease)
  • Gastroenteritis (stomach flu, except it’s not the flu, it’s not influenza, it’s enterovirus, STOP CALLING IT STOMACH FLU)
  • Croup (parainfluenza virus)
  • Pink eye (mind blown, right?), well about 75-80% of cases anyway
  • Pneumonia, bronchitis (mind blown again – the majority of pneumonia in kids is caused by viruses)
  • Mono (mononucleosis)
  • Viral meningitis (most of them are miserable but benign)

Viruses that are quite serious and might actually kill you, but I still can’t treat them with antibiotics:

  • THE FLU (influenza for realz)
  • RSV (respiratory syncytial virus)
  • Hepatitis B, A, C
  • HIV
  • Ebola
  • West Nile Virus
  • Zika (deadly or devestating if you happen to be a fetus)
  • Measles
  • Chicken Pox (Varicella)
  • HPV (human papilloma virus)

Bacteria that will often resolve on their own (but might not, so you’ll notice we usually treat them anyway):

  • The common ear infection (about 80% of cases would resolve without antibiotics in about 3 days)
  • Strep throat (the acute illness will typically resolve without medication, we give antibiotics to prevent progression to rheumatic fever – this condition is crazy rare, but it’ll kill ya, so we treat all strep, even though we know the acute symptoms would probably resolve in a couple of days anyway)
  • Abscesses (a.k.a. boils) – the definitive treatment for an abscess is drainage of the pus, not antibiotics
  • Sinusitis – the common sinus infection would probably be just as effectively treated by sinus rinses as that Z-Pack they gave you at the urgent care

Bacteria that would definitely kill you (or at least seriously mess you up) without antibiotics:

  • Bacterial pneumonia
  • Bacterial meningitis
  • Urinary tract infections (particularly if they progress to a kidney infection – pyelonephritis)
  • Sepsis (bacteria from any local infection that’s spreading into the blood stream)
  • Joint infections and bone infections (septic arthritis, osteomyelitis)

Here’s another thing that’s important to understand – most bacterial infections in children are complications of an initial viral infection.  It starts with a common head cold – your child’s body is producing mucus in the middle ear, sinuses, lungs, etc.  Their immune system is suppressed a bit.  This creates an opportunity for bacteria in the neighborhood to move in and set up housekeeping.  Ear infections, pneumonia, sinus infections – these are all secondary infections that occur after you’ve had a virus for a while.  Now pay very close attention to what I’m about to tell you – there is nothing I can do to prevent these things from happening.  Coming in on day 1 of symptoms to “nip it in the bud”, “keep it from turning into something worse”, “keep it from getting worse” does not accomplish anything.  Your child’s immune system is already doing its best to prevent secondary bacterial infection.  Your kid is coughing.  That keeps mucus out of the lungs.  (So believe it or not, you don’t want to suppress that cough.  I know you think you do, but you don’t.)  I can’t prevent the secondary illness, BUT YOU MIGHT!  Keep your child well hydrated, suck out that mucus, keep them comfortable and make sure they get plenty of rest.  Know what to watch for that could indicate a bacterial infection.  Starting antibiotics at the onset of the viral illness will not prevent the secondary complications.

Actually, back that train up, there is ONE thing we can do to prevent the secondary complications of some viruses.  WE CAN VACCINATE!!  Don’t tell me you don’t want a flu shot in October, then come see me with your sick kid in January wanting me to “make sure it doesn’t get worse”.  (See post on the flu shot.)

NOW, you’re a caring and concerned parent and your child is sick.  How can you tell if your child is suffering from a viral infection or a bacterial infection?  A typical viral illness is going to go something like this:

Upper respiratory infection – cough (yes, even a really ugly cough), nasal congestion, can’t sleep, fever for 2-3 days, cough and congestion lasting 10-14 days (yes, really); I expect the symptoms to get worse over the first 3 days, stay the same for about 3 days, then start to get better and resolve after about 2 weeks, I expect the fever to last about 2-3 days then resolve

Upper respiratory infection with a bacterial complication (potentially, it might still be all viral but I at least want to take a look) – focal pain (ear hurts, throat hurts really bad, chest pain, facial pain), fever lasting longer than 3 days, fever for a few days that resolves for a few days and then COMES BACK (see post on fever), respiratory distress (retractions, abnormally fast breathing, nasal flaring, wheezing, stridor, grunting in an infant)

Symptoms that could still be viral but concerning enough to seek medical attention promptly – wheezing, stridor, barky cough, lethargy*, decreased urine output, rash, severe pain

Symptoms that DO NOT indicate a bacterial infection – green snot, yellow snot, white snot, Technicolor dream snot; “bad” cough, cough lasting longer than 3 days, really really bad congestion, gagging on mucus – all still part of the common cold

Stomach viruses (gastroenteritis) – vomiting for 1-3 days, diarrhea that usually starts on day 2-3 of illness and persists for 5-7 days; I do NOT expect severe abdominal pain or dehydration, watch out for these

Symptoms that worry me and make me want to see that kid – severe abdominal pain, vomiting longer than 3 days, dehydration (no urine output for more than 8 hours in a baby or toddler), vomiting for several days WITHOUT diarrhea, vomiting in association with severe headache or neck pain, lethargy*, diarrhea that persists longer than a week, blood in stool or vomit, dark green color in the vomit (that’s bile and bile is bad)

Sore throat – I do not expect parents to be able to differentiate between bacterial and viral causes of sore throat.  If your kid has a bad sore throat, especially with fever, come see me.

Rash – I cannot diagnose a rash over the phone.  I cannot diagnose a rash via text or facebook PM.  I cannot diagnose a rash with a box, I cannot diagnose a rash with a fox.  If your kid has a weird rash and you don’t know what it is, just come see me, OK?

If your kid is sick and you can’t tell if it’s a head cold or croup or pneumonia or ebola, COME SEE ME!  I won’t judge you!!! Particularly if your child has some underlying condition like asthma or something.  I went to school for this stuff.  I want you to have the above information so that we can discuss your child’s diagnosis and be on the same page.  We can talk about whether your child needs medication or not.  We can talk about things you can do to make your child more comfortable and relieve their symptoms.  We can talk about the symptoms you should be watching out for.  If your child needs an antibiotic, I’ll tell you.  It’s entirely possible that you might seek care on day 2 or 3 of illness and be told your child has a virus, only to return on day 4-5 and be told your child now has a secondary bacterial infection.  The first doctor did not “miss” the ear infection or pneumonia, it wasn’t there before.  If a doctor tells you your child has a viral illness, they should also be talking to you about the signs of secondary infection.  If they don’t, ask.  You deserve for someone to talk to you about this stuff.  Answering your questions is our job.

More readings!!


*Remember our discussion about lethargy in my fever post?  When I say “lethargic” I do not mean a usually-active child who is now subdued on the couch eating animal crackers watching Bubble Guppies.  I mean a child who is acting drunk, difficult to arouse, or mumbling and moaning in a child who is usually verbal.  Got it?  Cool.

2 thoughts on “Virus vs. Bacteria

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  1. NP Kat 💖 Doc Kate! This is beautifully done and your vaccination posts are stellar. I still grapple with these issues. I like your friendly, compassionate and frank style and will encorporate it in my practice! Thank you!


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