Viral infections are any illness you get from a virus (a small germ that uses your cells to reproduce). Common viral illnesses include colds, the flu, COVID-19, norovirus (“stomach flu”), HPV (warts) and herpes simplex virus (cold sores). Many viruses go away on their own, but some cause life-threatening or chronic illnesses.
Viral infections are illnesses you get from tiny organisms that use your cells to make more copies of themselves (viruses). Viral infections commonly cause respiratory and digestive illnesses, but viruses can also infect most other parts of your body.
A virus is a type of germ (pathogen) that’s so small, you can only see it under a microscope. All viruses carry a small piece of genetic information (DNA or RNA) inside a protective coating (capsid). You can think of it like an envelope carrying instructions. Our cells, on the other hand, are like an entire factory: They contain instructions and all the equipment needed to carry them out. These instructions tells us how to build proteins and make more cells.
Unlike you and me, viruses don’t have cells, which means they don’t have all the “machinery” they need to make more of themselves. So, if they want to make copies of their instructions (replicate), they have to break into our cells and use our machinery to do it. Viruses replicating is what makes you sick with a viral infection.
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Viruses and bacteria can cause similar symptoms, like fever, cough and rashes. The only way to know what kind of infection you have is to have a healthcare provider assess you. If you have symptoms that last more than a few days or that concern you, see your provider.
You might hear viruses described by what part of your body they infect, how they spread or what symptoms they cause. Some viruses, like herpes viruses and adenoviruses, can cause many different types of illness. Types of viral infections include:
Respiratory infections affect your nose, throat, airways and lungs. Many respiratory viruses can cause bronchitis, sinusitis, ear infections or pneumonia. Examples include:
Viral infections in your digestive system can affect your stomach and intestines (GI tract) or your liver. These include:
Hemorrhagic fevers affect how your blood clots and can weaken your blood vessels, causing potentially life-threatening bleeding. Examples include:
Sexually transmitted diseases are mainly spread by sexual contact, including oral, anal and vaginal sex. Examples include:
Exanthematous viral infections cause rashes that can appear as bumps or blisters on your skin or spots of blood under your skin. They can also cause respiratory or other symptoms. Examples of exanthematous infections include:
Some viruses attack the cells of your nervous system (your brain and spinal cord). These can cause paralysis, swelling of your brain or its covering (encephalitis or meningitis) and other life-threatening conditions. Examples include:
Congenital viral infections are those you’re born with. They pass from a pregnant person to the fetus while it’s developing or during birth. Depending on the virus, this can cause various health issues, including vision or hearing loss, developmental delays and neurological conditions. Viruses known to cause congenital infections include:
All of us will get viral infections at some point. But you’re at increased risk of serious illness from certain types of viruses if you:
Symptoms of a viral infection depend on where you’re infected, but some common ones include:
Many viral infections don’t cause any symptoms.
Many different types of viruses can cause infections, though only a few infect humans. They can get into your body through your nose, mouth, eyes, anus or genitals, or through a break in your skin. Once there, they get inside of your cells and use them to make more copies of themselves.
Common ways you can get viral infections include:
Yes, nearly all viral infections are contagious (can spread from person to person). Viruses need to infect living things to reproduce, so human viruses survive by spreading between people.
A healthcare provider can often diagnose you with a viral infection by listening to your symptoms and examining you. To diagnose a specific virus, your provider might swab your nose or throat or take a blood sample for testing.
If they think you have a viral infection causing serious inflammation in your lungs, brain or another internal organ, your provider might get X-rays, ultrasound, MRI or CT imaging. Imaging can’t diagnose a viral infection, but it can help your provider understand how it’s affecting your body.
Your provider might send body fluid or tissue samples to a lab to look for signs of a viral infection (viral DNA/RNA, antibodies or antigens). Types of samples they might take include:
Specific medications are only available for a few viral infections. For viruses that can cause life-threatening or chronic illness, a provider may prescribe antiviral medications or treatment that prevents you from getting sick after being exposed to a virus.
For infections that rarely cause serious illness, like the common cold, you can usually treat the symptoms at home while you wait for them to go away on their own.
Medications a healthcare provider might prescribe to treat viral infections include antiviral medications, convalescent plasma and post-exposure prophylaxis.
Antiviral medications stop viruses from making more copies of themselves (replicating). They can be used to manage chronic infections or shorten the length of some respiratory infections. They can only treat one type of virus — they don’t work on other viruses. Antivirals are available for the flu, COVID-19, hepatitis B and C, HIV and mpox.
In some cases, providers can treat someone with a life-threatening viral infection with a blood transfusion. For convalescent plasma treatment, someone who has recovered from an infection with the same virus donates their blood. Your provider gives you the plasma from the blood through an IV. The plasma contains antibodies, which help you fight the infection. Providers have treated some cases of COVID-19 and Ebola with convalescent plasma.
Treatments for certain life-threatening viral infections can prevent you from getting sick after being exposed. A provider has to give you these treatments before you have symptoms. These include antiviral medications and immunoglobulin (antibody) treatment. Post-exposure prophylaxis is available for:
No, antibiotics can’t treat or cure illnesses caused by a virus. You provider will only give you antibiotics if they think you have a bacterial infection.
If you have a mild respiratory or GI tract infection without complications, you can often manage the symptoms at home. Using over-the-counter (OTC) medications, drinking plenty of fluids and getting enough rest can help get you through until you’ve fought off the virus. It’s always a good idea to ask a healthcare provider what medications are OK to take.
One of the best ways to reduce your risk of a viral illness is to get vaccinated. A healthcare provider can tell you which vaccinations are recommended for you. Vaccinations are available for:
Other ways to protect yourself and others from viruses include:
What to expect depends on what kind of viral infection you have. You can usually manage less serious infections, like the common cold or skin infections, at home. Other viral infections can cause life-threatening or long-lasting illness.
Viral infections can vary a lot in how long they last, for instance:
Viral infections can cause serious complications, both shortly after getting sick or years later. Complications include:
Contact a healthcare provider if:
Go to the nearest ER or seek immediate medical attention if you have signs of a serious infection, including:
A note from Cleveland Clinic
Viral infections are common and usually not serious. We manage colds, the occasional stomach bug, and bumps and sores on our skin on a regular basis. But some viruses cause life-threatening illnesses, and some common illnesses — like the flu — can turn serious. This is why it’s important to take steps to protect yourself and those around you from viral infection. Vaccinations, good hand-washing habits and safe sex can all help you stay healthy.
Last reviewed by a Cleveland Clinic medical professional on 11/23/2022.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy