Bacteria and viruses can cause many common infections. But what are the differences between these two kinds of infectious organisms?

Bacteria are tiny microorganisms that are made up of a single cell. They are very diverse, and can have a large variety of shapes and structural features. Bacteria can live in almost every conceivable environment, including in or on the human body.

Only a handful of bacteria cause infections in humans. These bacteria are referred to as pathogenic bacteria.

Viruses are another type of tiny microorganism, although they’re even smaller than bacteria. Like bacteria, they’re very diverse, and have a variety of shapes and features.

Viruses can invade the cells of your body, using the components of your cells to grow and multiply. Some viruses even kill host cells as part of their life cycle.

Many bacterial infections are contagious, meaning that they can be spread from person to person. There are many ways this can occur, including:

  • close contact with a person who has a bacterial infection, including touching and kissing.
  • contact with the body fluids of an infected person, particularly after sexual contact, or when an infected person coughs or sneezes
  • transmission from mother to child during pregnancy or birth
  • coming into contact with contaminated surfaces, such as doorknobs or faucet handles, and then touching your face, nose, or mouth

In addition to spreading from person to person, bacterial infections can also be spread through the bite of an infected insect. Additionally, consuming contaminated food or water can also lead to infection.

Some examples of bacterial infections include:

Like bacterial infections, many viral infections are also contagious. They can be spread from person to person in many of the same ways, including:

  • coming into close contact with a person who has a viral infection
  • contact with the body fluids of a person with a viral infection
  • transmission from mother to child during pregnancy or birth
  • coming into contact with contaminated surfaces

Also, similarly to bacterial infections, viral infections can be spread by the bite of an infected insect or through consuming food or water that has been contaminated.

Some examples of viral infections include:

A cold can cause a stuffy or runny nose, sore throat, and low fever, but is a cold bacterial or viral?

The common cold is caused by a number of different viruses, although rhinoviruses are most often the culprit. There’s not much you can do to treat a cold except wait it out and use over-the-counter (OTC) medications to help relieve your symptoms.

In some cases, a secondary bacterial infection may develop during or following a cold. Common examples of secondary bacterial infections include:

You may have developed a bacterial infection if:

  • symptoms last longer than 10 to 14 days
  • symptoms continue to get worse rather than improving over several days
  • you have a higher fever than is normally observed with a cold

Can you use mucus color to determine if it’s a bacterial or viral infection?

You should avoid using mucus color to determine whether you have a viral or bacterial infection.

There’s a long-held belief that green mucus indicates a bacterial infection that requires antibiotics. In fact, green mucus is actually caused by substances released by your immune cells in response to a foreign invader.

You can have green mucus due to many things, including viruses, bacteria, or even seasonal allergies.

When you experience symptoms such as nausea, diarrhea, or abdominal cramps, you likely have a stomach bug. But is it due to a viral or bacterial infection?

Stomach bugs generally fall into two categories based on how they’re acquired:

  • Gastroenteritis is an infection of the digestive tract. It’s caused by coming into contact with stool or vomit from a person with the infection.
  • Food poisoning is an infection of the digestive tract caused by consuming contaminated food or liquids.

Gastroenteritis and food poisoning can be caused by both viruses and bacteria. Regardless of the cause, many times your symptoms will go away in a day or two with good home care.

However, symptoms that last longer than three days, cause bloody diarrhea, or lead to severe dehydration may indicate a more severe infection that requires prompt medical treatment.

Sometimes your doctor may be able to diagnose your condition based on your medical history and your symptoms.

For example, conditions like measles or chickenpox have very characteristic symptoms that can be diagnosed with a simple physical examination.

Additionally, if there’s a current epidemic of a particular disease, your doctor will factor that into their diagnosis. An example is influenza, which causes seasonal epidemics in the cold months of every year.

If your doctor wants to know what type of organism may be causing your condition, they may take a sample to culture. Samples that can be used for culture vary by the suspected condition, but can include:

When a microorganism is cultured, it allows your doctor to identify what’s causing your condition. In the case of a bacterial infection, it can also help them determine which antibiotic may be helpful in treating your condition.

Antibiotics are medications used to treat bacterial infections. There are many different types of antibiotics, but they all work to keep bacteria from effectively growing and dividing. They’re not effective against viral infections.

Despite the fact that you should only take antibiotics for a bacterial infection, antibiotics are often requested for viral infections. This is dangerous because over-prescription of antibiotics can lead to antibiotic resistance.

Antibiotic resistance occurs when bacteria adapt to be able to resist certain antibiotics. It can make many bacterial infections more difficult to treat.

If you’re prescribed antibiotics for a bacterial infection, take your entire course of antibiotics — even if you begin to feel better after a couple of days. Skipping doses can prevent all of the pathogenic bacteria from being killed.

There’s no specific treatment for many viral infections. Treatment is typically focused on relief of symptoms while your body works to clear the infection. This can include things like:

  • drinking fluids to prevent dehydration
  • getting plenty of rest
  • using OTC pain medications such as acetaminophen (Tylenol) or ibuprofen (Motrin, Advil) to relieve aches, pains, and fever
  • taking OTC decongestants to help with a runny or stuffy nose
  • sucking on a throat lozenge to help ease a sore throat

Antiviral medications

In some cases, your doctor may prescribe an antiviral medication to help treat your condition.

Antiviral medications inhibit the viral life cycle in some way. Some examples include medications like oseltamivir (Tamiflu) for influenza infection or valacyclovir (Valtrex) for herpes simplex or herpes zoster (shingles) virus infection.

You can follow the tips below to help prevent becoming ill with a bacterial or viral infection:

Practice good hygiene

Be sure to wash your hands before eating, after using the bathroom, and before and after handling food.

Avoid touching your face, mouth, or nose if your hands aren’t clean. Don’t share personal items such as eating utensils, drinking glasses, or toothbrushes.

Get vaccinated

A multitude of vaccines are available to help prevent various viral and bacterial illnesses. Examples of vaccine-preventable diseases include:

Talk to your doctor about the vaccines that are available to you.

Don’t go out if you’re sick

Stay home if you’re ill to help prevent spreading your infection. If you must go out, wash your hands frequently and sneeze or cough into the crook of your elbow or into a tissue. Be sure to properly dispose of any used tissues.

Practice safe sex

Using condoms can help prevent getting sexually transmitted diseases (STDs). Limiting your number of sexual partners has been shown to reduce your risk of getting an STD.

Make sure that food is cooked thoroughly

Make sure all meats are cooked to the proper temperature. Be sure to thoroughly wash any raw fruits or vegetables before eating. Don’t let leftover food items sit at room temperature. Instead, refrigerate them promptly.

Protect against bug bites

Be sure to use insect repellent containing ingredients such as DEET or picaridin if you’re going to be outside where insects such as mosquitoes and ticks are prevalent. Wear long pants and long-sleeved shirts, if possible.

Many common infections can be caused by either bacteria or viruses, and these infections are spread in many of the same ways.

Sometimes your doctor can diagnose your condition by a simple physical examination. Other times, they may need to take a sample to determine if a bacterial or viral infection is causing your illness.

Antibiotics are used to treat bacterial infections. Treatment of viral infections involves treating symptoms while the infection runs its course, although in some cases antiviral medications may be used.

You can help to prevent getting sick with or spreading bacterial and viral infections by practicing good hygiene, getting vaccinated, and staying home when you’re sick.