What are the signs of an infection?

An infection happens when a germ enters the body and starts to multiply. This infection causes symptoms and ramps up the body’s defenses.

Both symptoms and the body’s reaction to the virus can be signs of infection. These include everything from congestion and sneezing to rashes, vomiting, or a fever.

Different germs cause different signs of infection. Most commonly, the germ is a virus or a bacteria. However, parasites and fungi can also cause infections.

Signs of your body fighting an infection can be minor or very serious. The symptoms of infection will depend on:

  • The type of germ.
  • Your immune system response.
  • Your overall health.

If you’ve had a certain virus before, your immune system can recognize and destroy it earlier, decreasing your symptoms.

Most commonly, infections spread in the nose and throat. More than 200 different viruses can cause the common cold.

Germs can infect any body parts, including the skin, lungs, and digestive tract. The most serious infections happen in the blood, heart, or brain.

Many infections will go away as the immune cells destroy the germ. In rare cases, however, infections can be life-threatening. If you have serious symptoms of an infection, you should see a doctor at a hospital or clinic right away.

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Bacterial Infections

Bacteria are a type of germ. They are tiny single cells that live on their own. We come in contact with them in the environment or when they’re infecting other people or animals.

Bacteria enter the body in many ways. It can enter through a cut, along with food, or through an insect bite.

People get bacterial infections by touching surfaces that contain them and then touching their mouth or another way into the body. Bacteria can also pass from one person to the next through touching hands, physical intimacy, or sharing cutlery.

Most types of bacteria do not cause infection. Most bacteria are good for the body; bacteria help us break down food, for example.

But some types of bacteria can be harmful. When harmful bacteria spreads in the body and causes symptoms, it’s a bacterial infection.

Sometimes, bacterial infections can become life-threatening. People with weakened immune systems due to an underlying condition or age may be more prone to bacterial infections.

What are the signs of an infection caused by bacteria?

Bacterial infections can cause a wide range of symptoms, depending on where the bacteria is spreading in the body. If you have a bacterial infection, you may have one or more of the following symptoms:

  • Fever.
  • Cough that produces greenish or brownish mucus.
  • Redness, warmth, pain, or swelling at a wound or intravenous line site.
  • Abscesses (pus-filled sores) on the skin or in the mouth.
  • A rash.
  • Fatigue.
  • Diarrhea.
  • Vomiting.
  • Painful or burning urination.
  • Muscle or joint pain.
  • Headache.

Bacterial infections can last for days, weeks, or even longer. They can also occur just after a viral infection. This is because fighting a virus can wear down the immune system and make it easier for bacterial infections to take hold.

How to treat a bacterial infection

Most proven bacterial infections are treated with antibiotics, except food poisoning.

In some cases, the doctor may be able to diagnose a bacterial infection, like an ear infection, based on your symptoms alone. Usually, however, the doctor can also do a blood test, urine test, or swab of other fluid. Then they can send it to a lab to look for certain types of bacteria.

Your doctor will often prescribe antibiotics if they diagnose your bacterial infection. Antibiotics for bacterial infections include:

  • Pills or liquid taken by mouth.
  • Cream to rub on the skin.
  • Liquid given into the vein (IV) at the hospital.

The type of antibiotic depends on the type of bacterial infection. You should not use antibiotics prescribed for a previous bacterial infection to treat a new one without first checking with your doctor.

You should also always follow the instructions for an antibiotic prescription. This means taking them as often as prescribed, for as long as prescribed.

If you stop taking antibiotics too soon or miss doses, the bacteria may not completely go away. In addition, bacteria can get stronger and become tougher to treat. Doctors call this antibiotic-resistant bacteria.

Viral Infections

A viral infection occurs when a virus enters the body. A virus is a complex of proteins, genetic information, and fats that take over our cells. They use our cells to make more viruses.

Just like bacteria, virus particles can enter the body in many ways. Most commonly, people breathe in viral particles breathed, sneezed, or coughed out by others. Viruses can also spread through touch, sexual fluid, food, and insect bites, depending on the virus.

Similar to bacteria, viruses make copies of themselves in the body. They can damage cells and trigger an immune response, leading to symptoms.

Common viruses infect many different tissues in the body. These include:

  • Lungs, throat, nose, and sinuses.
  • The stomach and intestines.
  • Liver or other vital organs.
  • White blood cells.
  • Heart and the tissue around it (pericardium).
  • Brain and the tissue around it (meninges).

What are the signs of an infection caused by a virus?

Symptoms show up even after few hours to days of exposure. However, with some viruses, like human immunodeficiency virus (HIV), symptoms may not show up for months or years.

Viruses infect specific parts of the body. For example, a respiratory virus can cause a cold and stuffy nose, while a stomach virus can cause diarrhea and fever.

Common symptoms of a viral infection may include one or more of the following:

  • Fever of above 100 F(38 C).
  • Sore muscles.
  • Sore joints.
  • Cough.
  • Sore throat.
  • Runny nose.
  • A rash.
  • Warts.
  • Diarrhea.
  • Headache.

How to treat a viral infection

Most common viral infections will get better on their own. However, some viruses need treatment.

Older people, very young kids, and people with weak immune systems or chronic conditions are likelier to get sick from viruses. People with more risk factors should see a doctor sooner if they have symptoms of an infection.

The doctor can run tests to determine the cause of an illness. Antiviral medications are also available for viruses like COVID and the flu. However, antibiotics do not work against viruses and can cause unpleasant side effects, like diarrhea.

Serious Symptoms of an Infection to Get Help For Right Away

Most people can recover from a viral and bacterial infection at home. Get rest, drink lots of fluids, and take over-the-counter pain relievers called NSAIDs to reduce a fever or relieve a sore throat.

For infections that cause digestive distress, slowly introduce mild foods after the vomiting has stopped. The BRAT diet is a common suggestion — the acronym stands for bananas, rice, applesauce, and toast.

For those that cause cough or congestion, talk to your doctor about what over-the-counter medicines could help your symptoms.

For some, bacterial and viral infections can be serious. Visit an emergency department or urgent care clinic if you have any of these serious signs of infection:

  • Shortness of breath.
  • A fever that lasts beyond three to four days.
  • Sudden confusion or disorientation.
  • A faster or slower heartbeat than usual.
  • Dehydration — dark-colored pee, not peeing regularly.
  • Inability to keep food or water down.
  • Extreme pain.
  • Sweating for no reason.

Dr. Larry Bush. Fever in adults. Merck Manual. Link

Centres for Disease Control and Prevention. Be antibiotics aware: Smart use, better care. Link

Centres for Disease Control and Prevention. Common Cold. Link

Centres for Disease Control and Prevention. How infections spread. Link

Dr. Laura Kramer. Overview of viral infections. Merck Manual. Link

National Institutes of Health. Viral Infections. Link

National Institutes of Health. Bacterial infections. Link

National Institutes of Health. Understanding a common cold virus. Link

Sepsis Alliance. Bacteria infections. Link

About Infectious Diseases

If you have a disease caused by bacteria, fungi, parasite, or virus, the UPMC Center for Care of Infectious Diseases can help. Our team of experts is specially trained in the prevention and treatment of infectious diseases, including of HIV-AIDs, postsurgical and transplant infections, illnesses caused by international travel, and more. We research infectious diseases and participate in clinical trials to learn more and develop better treatment and prevention methods. Visit our website to find an expert near you.