Virus vs bacteria: the differences explained

A CSIRO survey found 92% of Aussies didn’t know the difference between viral and bacterial infections. We explain the differences.

You experience viruses and bacterial infections throughout your life. But do you know what they are and how they’re treated? We answer your top questions.

What’s the difference between a virus and bacteria?

Bacteria are microorganisms that live almost everywhere. Some are natural flora on human skin, gut, airways and can be beneficial. Many can cause a range of infections.

On the other hand, viruses are much smaller than bacteria. They cause infection by entering the healthy cells of living hosts, like people and animals, and multiplying.

What are some examples of bacterial and viral infections?

Streptococcus bacteria are common causes of throat and ear infections, and salmonella and campylobacter are common causes of gastro.

Common cold, flu, chickenpox, human papillomavirus (HPV), HIV/AIDS are all viruses. COVID-19 is caused by a type of virus, called a coronavirus.

How do bacteria and viruses enter human cells?

Bacteria enters the body through cuts; in contaminated food or water; or through contact with an infected person, infected faeces or contaminated surfaces.

Viruses are generally spread from one person to another in droplets when someone coughs, sneezes, vomits or has sex. They may also be spread in bites from infected animals or insects.

How are bacterial and viral infections diagnosed?

To determine if your infection is bacterial or viral, your doctor may take a sample of your urine, stool (faeces) or blood, to identify the culprit under a microscope.

Are antibiotics effective in treating viruses or bacteria?

Doctors usually treat bacterial infections with antibiotics to kill bacteria or stop multiplication. Antibiotic resistance is growing, so antibiotics may be prescribed only for serious infections. Finish your full course of antibiotics even after you feel better to stop antibiotic resistance.

Antibiotics are generally useless against viral infections. Treatment of a virus generally includes management of symptoms. Some anti-viral medications are available for certain viruses.

Can vaccines protect you?

Yes, it’s possible to be vaccinated against some bacterial diseases like tetanus and whooping cough, and against viral infections such as measles, mumps, hepatitis A and B.

However, some viruses – like those that cause the common cold – are capable of mutating from one person to the next, making vaccination difficult.

This article first appeared in the November 2020 edition of Health Agenda magazine.