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Viral Infections
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Infections

Viral Infections

Viruses are tiny germs that hijack your cells to replicate, but their spread can often be mitigated through preventative hygiene and vaccination.

What are viruses?

Viruses are very tiny germs. They are made of genetic material (either DNA or RNA) inside of a protein coating. There are a huge number of viruses on earth. Only a small number of them can infect humans. Those viruses can infect our cells, which may cause disease. Some of the diseases that viruses can cause include the common cold, the flu, COVID-19, and HIV.

How are viruses spread?

Viruses can be spread in different ways:

  • Through droplets and particles that are breathed out by someone who has the infection. You might breathe in the droplets or particles, or they could land on your mouth, nose, or eyes.
  • By touching surfaces or objects that have the virus on them and then touching your mouth, nose, or eyes.
  • From the pregnant parent to the baby during pregnancy.
  • Through contaminated food or water.
  • By being bitten by an infected insect or animal.
  • Through sexual contact (usually vaginal, anal and oral sex) with someone who has the infection.

How do viruses cause disease?

Viruses are like hijackers. They invade living, normal cells. They then use those cells to multiply (make copies of themselves). This process is also called replication. The process can kill, damage, or change the infected cells. Sometimes this can make you sick. The symptoms can range from mild to very severe. Other times, your immune system may be able to fight it off and you may not have any symptoms.

Each different virus usually only infects one type of cell in your body. For example, hepatitis viruses affect the cells in the liver. HIV infects a certain type of immune system cell.

What are the treatments for viral infections?

For most viral infections, treatments can only help with symptoms while you wait for your immune system to fight off the virus. There are antiviral medicines to treat some viral infections. Antibiotics do not work for viral infections.

Can viral infections be prevented?

Vaccines can help prevent you from getting many viral diseases. You may be able to prevent some viral infections by:

  • Proper hand washing.
  • Paying attention to food safety.
  • Cleaning surfaces that may be infected with germs.
  • Avoiding contact with wild animals.
  • Preventing insect bites by using insect repellent when you go outdoors. If you travel to an area that has a high risk of diseases from insect bites, also wear long pants, shirts, and socks.
  • Practicing safe sex (using a condom every time you have anal, vaginal, or oral sex).
  • Avoiding close contact with people who are sick.

Frequently Asked Questions

The difference often comes down to the strength of the individual's immune system and the specific strain of the virus. Some people have pre-existing immunity from previous exposure or vaccination, which allows their bodies to neutralize the virus before it causes noticeable illness. Others may have a robust immune response that clears the virus quickly, resulting in only mild or no symptoms. Factors such as age, overall health, and genetic differences also play a role in how the body reacts to a viral invasion.
The most effective strategies include frequent handwashing with soap and water for at least 20 seconds, especially after touching shared surfaces or being in close contact with the sick person. Avoiding touching your face, particularly your eyes, nose, and mouth, is crucial because this is how viruses often enter the body. Additionally, maintaining physical distance, improving ventilation in shared spaces, and disinfecting high-touch surfaces like doorknobs and light switches can significantly reduce the risk of transmission within the household.
No, antibiotics are ineffective against viral infections and will not speed up recovery. Antibiotics are designed to kill bacteria or stop their growth, but they have no impact on viruses. Taking antibiotics when you do not need them can lead to side effects such as diarrhea, nausea, and allergic reactions. More importantly, unnecessary use of antibiotics contributes to antibiotic resistance, making it harder to treat actual bacterial infections in the future. For viral infections, treatment is usually supportive, focusing on rest, hydration, and managing symptoms with over-the-counter medications.
It is often difficult to distinguish between viral and bacterial infections based on symptoms alone, as both can cause fever, fatigue, and body aches. However, viral infections like the common cold or flu often present with a runny nose, sore throat, and cough, and symptoms may appear suddenly. Bacterial infections, such as strep throat or a urinary tract infection, may have more localized symptoms and can sometimes be more severe or persistent. The only way to know for sure is through medical testing, such as a rapid strep test or a culture, which can determine if antibiotics are necessary. Since antibiotics do not work on viruses, misdiagnosis can lead to unnecessary medication use.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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