Viral Infection

Viral infections are illnesses you get when tiny organisms (viruses) use your cells to make more copies of themselves. A virus is a type of germ that carries a small piece of genetic information (DNA or RNA) inside a protective coating (capsid). You can think of it like an envelope carrying instructions.

Viruses only carry instructions for making more copies of themselves. They need your cells’ machinery to read the instructions and make more viruses. This is what makes you feel sick.

Viral infections commonly cause respiratory and digestive illnesses. But viruses can also infect most other parts of your body, too.

Types

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
• Digestive system infections
• Sexually transmitted infections (STIs)
• Rash-causing (exanthematous) infections
• Nervous system infections
• Viral hemorrhagic fevers
• Congenital infections

Respiratory infections

Respiratory infections affect your nose, throat, airways and lungs. Many respiratory viruses can cause bronchitis, sinusitis or pneumonia. If the virus causes swelling in the tubes that connect your throat and ears, you can also get an ear infection.

Examples of viral respiratory infections include:

• Common cold (usually caused by rhinovirus)
• COVID-19
• Flu (influenza)
• Human metapneumovirus (hMPV)
• Parainfluenza
• Respiratory syncytial virus (RSV)

Viral infections in your digestive system

Some viruses infect your stomach, intestines or liver. Examples include:

• Norovirus, rotavirus and astrovirus can cause gastroenteritis, sometimes called “stomach flu.”
• Hepatitis viruses cause liver disease. These infections often last a long time (chronic).

Sexually transmitted viral infections

Sexually transmitted infections are mainly spread by sexual contact, including oral, anal and vaginal sex. Examples include:

• Genital herpes (HSV)
• Hepatitis B
• Human immunodeficiency virus (HIV)
• Human papilloma virus (HPV)/genital warts

Exanthematous viral infections

These viruses 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:

• Chickenpox
• Fifth disease
• Measles
• Mpox
• Roseola
• Rubella

Nervous system infections

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 and other life-threatening conditions. Examples include:

• Epstein-Barr virus (EBV)
• Polio
• Rabies
• Shingles
• West Nile virus

Viral hemorrhagic fevers

Hemorrhagic fevers affect how your blood clots and can weaken your blood vessels. This can cause life-threatening bleeding. Examples include:

• Ebola
• Hantavirus
• Severe dengue
• Yellow fever

Congenital viral infections

You’re born with congenital viral infections. They pass from a pregnant woman to the fetus during pregnancy 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:

• Cytomegalovirus (CMV)
• Rubella
• Zika virus

Symptoms of viral infections

Symptoms depend on where you’re infected. Some common symptoms of viral infections include:

• Flu-like symptoms: fever, headache, body aches, fatigue
• Upper respiratory symptoms: sore throat, cough, sneezing
• Digestive symptoms: nausea, vomiting, diarrhea
• Skin conditions: rashes, sores, blisters, warts
• Neurological symptoms: Headaches, seizures, confusion, neck stiffness

Some infections don’t cause any symptoms.

Viral infection causes

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 make more copies of themselves.

How do you get a viral infection?

You can get viral infections from:

• Particles released from coughing, sneezing or talking
• Close contact with other people
• Contact with poop (including changing diapers)
• Surfaces or objects that someone with a virus has touched (like countertops, doorknobs, phones or kids’ toys)
• Vaginal, oral or anal sex
• Bites from infected animals, mosquitoes or ticks
• Contaminated food or water

Are viral infections contagious?

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.

Risk factors

All of us will get many viral infections during our lives. But you’re at increased risk of serious illness from certain types of viruses if you:

• Are under 5 or over 65
• Have certain health conditions, like diabetes, asthma, COPD or other chronic lung disease
• Have a weakened immune system
• Are pregnant

Complications

Viral infections can cause serious complications, both shortly after getting sick or years later. Depending on the infection, you can be at risk for inflammation in your lungs, brain, or lining of your brain and spinal cord. Hemorrhagic fevers can cause life-threatening bleeding.

Some infections can stay in your body for a long time, even after you get better. Sometimes, viruses like Epstein-Barr, HPV, herpes simplex and varicella can reactivate in your body and cause symptoms years later.

Some viruses can cause cancer (oncoviruses) many years after getting infected. Viruses linked to specific cancers include:

• Epstein-Barr virus
• Hepatitis B and C
• HIV
• HPV
• Human T-lymphotropic virus 1 (HTLV-1)
• Human herpesvirus 8 (HHV-8)

How doctors diagnose viral infections

A healthcare provider can often diagnose a viral infection by asking about your symptoms and examining you. Many times, you may not need testing.

Providers commonly test for respiratory viruses with a swab of your nose or throat. For other types of infections, your provider might test samples of:

• Blood
• Spit (saliva)
• Phlegm or mucus (sputum)
• Skin or other affected tissue
• Fluid around your brain and spinal cord (CNS fluid)
• Pee (urine)
• Poop (stool)
• Cells from your cervix (Pap smear)

If they think an infection is causing serious inflammation in your lungs, brain or another internal organ, your provider might get imaging. Imaging can’t diagnose a viral infection, but it can help your provider understand how it’s affecting your body.

A provider may also perform testing if they need to determine if the infection is viral or bacterial.

How are viral infections treated?

For infections that rarely cause serious illness, like the common cold, you can usually treat symptoms at home while you wait for them to go away on their own.

For potentially serious infections, treatment options could include:

• Antiviral medications: Each antiviral only works in a specific type of virus and often only work if taken soon after symptoms start. Antivirals are available for the flu, COVID-19, hepatitis B and C, HIV and mpox.
• Convalescent plasma: In some cases, providers can treat someone with a life-threatening viral infection with a blood transfusion.
• Post-exposure prophylaxis: Treatments for certain serious viral infections can prevent you from getting sick if you’re treated right away after exposure. Post-exposure prophylaxis is available for HIV, rabies, hepatitis and chickenpox.

Do antibiotics work on a viral infection?

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.

When should I see my healthcare provider?

Contact a healthcare provider if:

• You have symptoms of a viral infection that aren’t getting better or are getting worse after several days.
• You have symptoms of the flu or COVID-19 and are at risk for serious illness. Your provider may be able to treat you with antiviral medications.
• You’ve been exposed to HIV, rabies, hepatitis or chickenpox. You need post-exposure prophylaxis as soon as possible after exposure.

Go to the nearest ER or seek immediate medical attention if you have signs of a serious infection, including:

• High fever (103 degrees Fahrenheit/39.4 degrees Celsius or higher)
• Difficulty breathing
• Chest pain
• Coughing up blood or vomiting blood
• Severe belly (abdominal) pain
• Confusion or other mental changes

How long do viral infections last?

How long an infection lasts can vary a lot. For example:

• Respiratory infections can last a few days to two weeks.
• A wart on your skin can last for a year or longer.
• Hepatitis B and C can cause chronic infections that last for years.
• HIV infections aren’t curable and are lifelong.

You can reduce your risk of many of the most serious viral illnesses by getting vaccinated against them. Your healthcare provider can let you know which vaccinations are recommended for you or your child. This might include vaccinations against:

• Chickenpox
• COVID-19
• Flu
• Hepatitis A
• Hepatitis B
• Human papillomavirus (HPV)
• Measles, mumps and rubella
• Polio
• Rabies
• Rotavirus
• RSV
• Shingles

Other ways to protect yourself and others from viruses include:

• Wash your hands frequently, especially during cold and flu season. Wash after going to the bathroom and before preparing food or eating.
• Practice safe food habits. This includes storing food properly, heating meat and poultry to a safe temperature, and washing or peeling fruits and vegetables before eating.
• Use a condom or dental dam during any kind of sex. If you and your partner only have sex with each other, you can be tested and treated for STIs.
• Protect yourself from bug bites. Wear protective clothing, use bug spray and sleep under mosquito netting if necessary.
• Don’t handle wild or aggressive animals. Don’t leave your pets outside unsupervised, where they could potentially get bitten by an animal with rabies.
• Avoid being around other people if you’re sick. Always cough and sneeze into your elbow to reduce the rest of spreading germs to others.
• Get post-exposure prophylaxis. Talk to a provider right away if you think you’ve been exposed to rabies, HIV, hepatitis or chickenpox.