What is a viral infection?
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.
What is a virus?
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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How do you tell if a disease is viral or bacterial?
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.
What are the types of viral infections?
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.
- Viral hemorrhagic fevers.
- Sexually transmitted infections (STIs).
- Exanthematous (rash-causing) infections.
- Neurological infections.
- Congenital infections.
Respiratory infections
Respiratory infections affect your nose, throat, airways and lungs. Many respiratory viruses can cause bronchitis, sinusitis, ear infections or pneumonia. Examples include:
- Common cold (usually caused by rhinovirus).
- The flu (influenza).
- COVID-19.
- Respiratory syncytial virus (RSV).
- Human metapneumovirus (hMPV).
- Parainfluenza.
Viral infections in your digestive system
Viral infections in your digestive system can affect your stomach and intestines (GI tract) or your liver. These 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).
Viral hemorrhagic fevers
Hemorrhagic fevers affect how your blood clots and can weaken your blood vessels, causing potentially life-threatening bleeding. Examples include:
Sexually transmitted viruses
Sexually transmitted diseases are mainly spread by sexual contact, including oral, anal and vagin*l sex. Examples include:
- Human immunodeficiency virus (HIV).
- Human papilloma virus (HPV)/genital warts.
- Genital herpes (HSV).
- Hepatitis B.
Exanthematous viral infections
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:
Neurological 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 (encephalitis or meningitis) and other life-threatening conditions. Examples include:
Congenital viral infections
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:
- Cytomegalovirus (CMV).
- Rubella.
- Zika virus.
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Who do viral infections affect?
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:
