BHealthy Blog

Bacteria and Viruses: What’s the Difference?

By Sarah-Catherine Formiller, Pharmacy Resident, Baptist Health Medical Center-North Little Rock

Bacterial and viral infections have many things in common. Both types of infections are caused by microbes (bacteria and viruses) and are spread by things such as coughing and sneezing, contact with infected people, surfaces, food, water, pets, livestock, or insects such as fleas and ticks.

Bacterial and viral infections can cause similar symptoms such as coughing and sneezing, fever, inflammation, vomiting, diarrhea, fatigue, and cramping. All of these are ways the immune system tries to rid the body of infectious organisms.

But bacterial and viral infections are not the same in many other important respects. These differences are mostly due to the organism’s structural differences and the way they respond to medications.

Microscopic Differences

Bacteria and viruses, although too small to see without a high-powered microscope, have many differences in their structure. Bacteria are more complex. They can reproduce on their own. Bacteria have existed for about 3.5 billion years, and bacteria can survive in different environments, including extreme heat and cold, radioactive waste, and the human body.

Most bacteria are harmless, and some actually help by digesting food, destroying disease-causing microbes, fighting cancer cells, and providing essential nutrients. Less than one percent of bacteria cause diseases in people.

Viruses are much smaller. The largest of them are smaller than the smallest bacteria. Unlike bacteria, viruses can’t survive without a host. They can only reproduce by attaching themselves to cells. In most cases, they reprogram the cells to make new viruses until the cells burst and die. In other cases, they turn normal cells into malignant or cancerous cells.

Also unlike bacteria, most viruses do cause disease, and they’re quite specific about the cells they attack. For example, certain viruses attack cells in the liver, respiratory system, or blood. In some cases, viruses target bacteria.

Diagnosing Bacterial and Viral Infections

You should consult your doctor if you think you have a bacterial or viral infection. Exceptions include the common cold, which is usually not life-threatening.

In some cases, it’s difficult to determine the origin of an infection because many ailments, including pneumonia, meningitis, and diarrhea can be caused by either bacteria or viruses. But your doctor often can pinpoint the cause by listening to your medical history and doing a physical exam.

If necessary, the doctor also can order a blood or urine test to help confirm a diagnosis, or order a culture test of tissue to identify bacteria or viruses. Occasionally, a biopsy of affected tissue may be required.

Treatment of Bacterial and Viral Infections

The discovery of antibiotics for bacterial infections is considered one of the most important breakthroughs in medical history. Unfortunately, bacteria are very adaptable, and the overuse of antibiotics has made many of them resistant to antibiotics. This has created serious problems, especially in hospital settings.

Antibiotics are not effective against viruses, and many leading organizations now recommend against using antibiotics unless there is clear evidence of a bacterial infection.

What Can I Do to Prevent Antimicrobial Resistance?

The best way to help prevent antimicrobial resistance is to learn the ABCs of antibiotics:

• Ask. Ask your health-care provider, “Are these antibiotics necessary?”

• Bacteria. Antibiotics do not kill viruses. They only kill bacteria.

• Complete the course. Take all of your antibiotics exactly as prescribed (even if you are feeling better).

Don’t pressure your health-care provider for antibiotics. You do not need antibiotics for colds or flu, most coughs or bronchitis, sore throats not caused by strep, runny noses, or most earaches. 

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