A virus is a small piece of genetic material that looks for a host to live inside and multiply. They are so small, in fact, that billions of viruses can fit on the head of a pin. Unlike bacteria, which can survive on its own, viruses need a living host to survive. When a virus enters the host cell, it takes over the cell's command center and begins to make copies of itself.

This article provides an overview of the most common types of viral infections, how they are transmitted, prevention, and treatment.

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Viral Infection

Viral infections occur when a virus enters the body and successfully takes over a host cell to begin the process of replicating. This can occur at the site of entry, also known as a localized infection, or the virus can spread throughout the body, causing a systemic infection.


The duration that an infected individual can be contagious varies significantly among viruses and can be impacted by the severity of the infection.

It is possible for a person to be a carrier of a virus without showing any symptoms but spreading the virus to people around them.

Virus Transmission

In order for a virus to live on within a population, it must move from host to host. This is known as viral shedding.

The virus typically exits the host by the same means it entered. Meaning, if the virus arrived by way of a droplet spread through a sneeze or cough, it can be shared with others the same way.

Viruses can be spread through either direct or indirect transmission:

  • Direct transmission can occur with any close physical contact, including skin-to-skin contact, sexual intercourse, or kissing. Droplet transmission is a form of direct transmission, wherein an infected individual coughs or sneezes and the respiratory droplets of that individual are inhaled by someone in close proximity.
  • Indirect transmission involves a vehicle or a vector to get the virus from host A to host B. Examples of transmission vehicles include food, water, or blood. A vector refers to a living messenger that delivers the virus from one host to another. Mosquitos and ticks are vectors.

Bacterial or Viral Infection?

Bacteria work differently than viruses. They can live on their own, meaning they don't require a host to survive.

Oftentimes viral infections can lead to bacterial infections if symptoms persist or worsen.

Both bacterial and viral infections can be treated with medication, though, overall, bacterial infections are more readily treatable. It's important to follow up with a healthcare provider for testing to determine the cause of illness and treatment options.

Common Viral Infections

Viral infections can affect different areas and systems of the body, the most common of which is the respiratory system. The following are some examples of common viral infections.

Viral Respiratory Infections

Viral Infections With Skin Rashes

Viral Sexually Transmitted Infections

 Other Viral Infections


Diagnosing viral infections is most commonly done by virological tests that look for the virus's genetic makeup, or DNA, or for antigens, as with the flu, COVID-19, and others.

Another method for diagnosing a viral illness is by performing an antibody test. These are blood tests that look for an active or past infection of a virus. Detection of antibodies in the blood can indicate immunity against the virus.


Treatments for viral respiratory infections, such as the common cold, are few and far between. Some symptoms of viral infections can be treated with medication, but ultimately the immune system is responsible for fighting off the virus itself. However, some viruses and viral illnesses, like HIV, the flu, and COVID-19, do have treatments available.

Preventing viruses from occurring in the first place is the best way to stay healthy.


Many viral infections can be completely avoided by a simple vaccine. Vaccines are currently available, among others, for:

Practicing good personal hygiene and lifestyle habits is another effective strategy toward preventing disease. This includes:

  • Engaging in safe sex practices to reduce the risk of sexually transmitted infections (STIs)
  • Practicing food safety techniques to minimize exposure to pathogens that can cause food poisoning
  • Learning about strategies to reduce your risk of contact with virus-bearing vectors, like mosquitoes and ticks

You should also make sure your vaccines are up to date to ensure protection against preventable disease.

Vaccine Effectiveness

Vaccines are consistently proven to be safe and effective against severe disease and death from many viruses. For example, the mRNA COVID-19 vaccines have proven to be 94%–96% effective at preventing severe illness and death. A study of healthcare workers, who are at high risk for contracting COVID-19 due to their proximity to infected people, found the Moderna mRNA vaccine to be 96.3% effective.


Viruses travel through the population by direct or indirect contact, and multiply by overtaking host cells. Most of the time viral infections run their course.

There are limited medications effective in treating respiratory viral infections, like the common cold, but there are treatments for others, including HIV and COVID-19. The best way to avoid viral infections is to practice good hygiene and get the available vaccines.

A Word From Verywell 

Viral infections are a part of life, and we are all at risk to get one at some point in our lives. Some can be as mild as the common cold, while others can be life-threatening. Viruses can spread rapidly, so it's important to minimize the risk of transmission if you find yourself sick with a virus. If you do contract a viral infection, monitor your symptoms and seek medical care if they become severe or persistent.

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