What to Know About COVID Viral Load

What Is Viral Load?

It’s simply the amount of virus doctors can find in your body. They might use blood, nasal swabs, or other bodily fluids to test the load for a particular virus.

People infected with the coronavirus that causes COVID-19 may have different viral loads. This goes for people who aren’t unvaccinated, as well as “breakthrough infections” that affect those who are.

Scientists are starting to learn more about how this affects your symptoms and your ability to get COVID-19 and give it to other people.

Does a Higher Viral Load for COVID-19 Make You More Contagious?

Doctors aren’t sure. Some studies seem to show that it does, but others seem to show less of an effect.

What does seem clear is that people with symptoms of COVID-19 are more contagious. And that the viral load tends to peak in the week after their symptoms first appear.

But, doctors say, that doesn’t always mean that those with the highest viral loads are most contagious. For example, someone with a higher viral load but no symptoms may be less contagious than someone with a low viral load who gets very sick.

Could Exposure to a Higher Viral Load Make You Sicker?

The short answer seems to be yes. The seriousness of symptoms from viral infections is often due directly to the amount of the virus that gets into your body. In addition, studies on two previous coronaviruses (SARS and MERS) showed people exposed to higher loads got sicker.

People with COVID-19 who continue to show a high viral load seem to have more serious symptoms. As viral loads go down, their chances of getting better go up.

These symptoms may get worse if you have an underlying condition, especially one that weakens your immune system.

Does a High Viral Load Mean You’ll Definitely Get Sick?

Not necessarily. Some studies seem to show no difference in viral loads when they compare infected people with symptoms to infected people without symptoms.

Scientists continue to study the subject to try to confirm the results and figure out the reasons.


How Do You Get Exposed to a High Viral Load?

It’s more likely if you’re physically close to someone who is both infected and in the first 5 days of symptoms. Doctors, nurses, and other health care workers are at especially high risk when they deal with people hospitalized for COVID-19.

Your risk might also be higher if you’re caring for loved ones sick with COVID-19.

And it may not be just one-time exposure to high viral loads that are problematic. Animal studies show that repeated exposure to low viral loads can be just as infectious as a single high dose.

How Does Vaccination Affect Viral Load?

If you’re vaccinated, you’re far less likely to get COVID-19 from someone else, no matter the viral load of the infected person. In the uncommon instances that a breakthrough infection happens, your symptoms are likely to be far less serious. You may even have none.

Even for the highly infectious Delta variant, which seems to produce high viral loads in both vaccinated and unvaccinated people, the load goes down far more quickly in those with the vaccine.

What’s the Best Way to Protect Against High Viral Load?

The best thing is to avoid infection altogether. That way you’re less likely to get sick and less likely to pass COVID-19 to others. Remember, COVID-19 can cause serious and even life-threatening illness.

By far the best way to avoid infection is to get vaccinated. It provides excellent protection both against infection and against the most serious aspects of the illness.

Pfizer, Moderna, and Johnson & Johnson make the three vaccines available in the U.S. Get vaccinated right away if you haven’t already. Talk to your doctor if you’re not sure if you’re a good candidate for the vaccine.

After that, follow CDC guidelines for mask wearing, hand-washing, and social distancing.

WebMD Medical Reference Reviewed by Michael W. Smith, MD on August 20, 2021



CDC: “Science Brief: COVID-19 Vaccines and Vaccination,” “Delta Variant: What We Know About the Science.”

Columbia University Irving Medical Center: “Viral Load as a Predictor of COVID-19 Patient Outcomes.”

Johns Hopkins Bloomberg School of Public Health: ““Delta Variant: New Data on COVID-19 Transmission by Vaccinated Individuals.”
Society of Critical Care Medicine -- Atiqur Rahman Khan, MD, Maternity and Children’s Hospital: “What is viral load and why are so many health workers getting sick?”

Tulane University: “Tulane study finds viral load is not a true indicator of COVID-19 transmission risk.”

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