How to Tell: Is This Bacterial or A Virus?

The short answer is: you can’t tell at all. Unless you’re a doctor.

Illnesses caused by bacteria and viruses are very similar. Some illnesses have a bacterial and a viral cause. We can tell the difference through your symptoms and medical history. We don’t prescribe antibiotics unless we’re absolutely sure–and what makes us sure is a physical exam and the lab. Depending on the illness, this is when we take a blood test, a throat culture, a urine or stool sample, a swab, and so on.

Viral (and Bacterial) Myths

Just because you have green mucus doesn’t mean it’s bacterial.

Just because it was sudden doesn’t mean it’s bacterial. A virus can lay dormant after infecting you while it multiplies. Symptoms ‘suddenly’ manifest when they’ve multiplied enough to issue a war cry to your immune system.

Hurry up and answer so I can take antibiotics or just wait it out!

People self-diagnose so they can self-medicate. We get it. It’s convenient in so many ways: it saves money, it saves time. But your aim is to get better, isn’t it?

Antibiotics are not effective against viruses. If you have a virus, a dose of antibiotic won’t help at all. Your immune system will have to duke it out with the virus instead. Self-treatment with antibiotics can cause more harm than good. For instance, antibiotics won’t help what you mistakenly thought was a strep throat, but it will be effective on the good bacteria present in your digestive system, killing them all and making you vulnerable.

This can cause havoc you might regret in the long run.

On the other hand, waiting it out because you suspect it’s only a bug can escalate your illness. Very important: many bacterial diseases, like bacterial meningitis, can leave severe permanent damage if not treated immediately.

Ask yourself instead: Am I ill enough to need a doctor?

Countless patients wait until they feel horrible. These are mainly teens and adults. Parents usually take their children to us immediately to be on the safe side.

Good road to take. To be on the safe side, phone or get yourself to a clinic if:

You feel faint, very weak and confused. This, combined with other symptoms like headache, fever, nausea and vomiting, are signs of a severe infection.

You are dehydrated, or in danger of getting dehydrated. A virus or bacteria attacking your digestive system needs immediate attention. If your symptoms include diarrhea, you need medication and rehydration. Dangers of dehydration aside, we always tell patients to drink a lot of clear fluids, because it helps the mucus that carries away infection. Thickened mucus won’t move and therefore won’t clear you up of your virus, which could lead to bacterial infection–bacteria thrives in mucus.

You can’t breathe. Severe coughing and shortness of breath are not something you can just sit out. Unless treated, pneumonia and asthma with bronchitis are life-threatening. See your doctor immediately.

You get worse. Viruses make you an ideal home for harmful bacteria. A viral infection can make you all cozy for a bacterial one to move in next. If you had a cold and it suddenly transformed into a cough-and-wheeze that leaves you weak, if your mild cough suddenly goes severe, it’s time to go to the doctor.

Is this bacterial or a virus? We’ll tell you.