How Infectious Is Coronavirus? | National interest

As the pandemic of COVID-19 spreads, people need to understand the basic facts about SARS-CoV-2, the virus that causes COVID-19, to make informed healthcare and public policy decisions. It became clear that there is. Two basic virological concepts of SARS-CoV-2, “infectious dose” and “viral load,” have recently received much attention.

As influenza virologists, these are the concepts we often think of when studying respiratory virus infections and transmissions.

What is the “infectious dose”?

Infectious load is the amount of virus needed to establish an infection. Depending on the virus, people need to be exposed to about 10 viral particles. Influenza virus – Or thousands Other human viruses Get infected.

Scientists do not know how many SARS-CoV-2 virus particles are needed to cause the infection. COVID-19 is clearly very contagious, either because it requires fewer particles to infect (a lower infection) or because infected people release large amounts of the virus into the environment.

What is “Viral Load”?

Viral load is the amount of a particular virus in a test sample taken from a patient. For COVID-19, this means how many viral genomes were detected Nasopharyngeal swab From the patient. Viral load reflects how well the virus replicates in infected people. The high viral load of SARS-CoV2 detected on the patient’s swabs means that numerous coronavirus particles are present in the patient.

Is high viral load associated with an increased risk of severe pneumonia or death?

Intuitively, it makes sense that the more viruses you have, the worse your illness becomes. But in reality the situation is more complicated.

in the case of Original SARS Or influenzaWhether a person develops mild symptoms or pneumonia depends not only on how much virus there is in the lungs, but also on the immune response and overall health.

At present, it is unclear if the SARS-CoV-2 viral load can indicate who develops severe pneumonia. two the study Lancet reports that people who develop more severe pneumonia tend to have an increased viral load on average when first hospitalized.

These studies also reported that viral load remained higher for more days in patients with more severe disease. However, the difference was not dramatic and people with similar viral loads developed both mild and severe disease.

Making the picture more complicated, Other the study It was found that some asymptomatic patients had similar viral load as those with COVID-19 symptoms. This means that viral load alone cannot clearly predict disease outcome.

Another common question is to increase the dose of virus during infection. For example, like the experience of health care workers, is it possible to get more serious illness from prolonged exposure to an infected person? Currently I’m not sure if this is the case.

Does a high viral load increase your ability to pass the virus on to others?

Generally, the more viruses in the respiratory tract, the greater the amount released during exhalation or coughing, but varies from person to person. Multiple the study Have got report Patients have the highest viral load of coronavirus at diagnosis.

This means that patients will be more effectively infected with COVID-19 at the onset of the disease or before they know they are sick. This is bad news. This means that people who appear healthy can transmit the virus to others.

Why is it difficult to answer the basic questions about SARS-CoV-2 viral load?

Researchers like us usually characterize viruses from a combination of highly controlled studies in animal models and epidemiological observations from patients.

However, because SARS-CoV-2 is a new virus, the research community is just beginning controlled experiments. Therefore, all the information we have comes from observing patients who are infected in different ways, have different underlying health conditions, and are of different ages and genders. This diversity makes it difficult to draw strong conclusions that apply to everyone from observational data alone.

Where the uncertainty of viral load and infectious load leaves us?

Studying viral load and infectious dose is probably important for health care providers to make better decisions. In the rest of us, it is clear that the virus can be transmitted efficiently from person to person, regardless of the patient’s viral load or SARS-CoV-2 infection, thus reducing exposure to the virus. Is the best

Current social distance practices and limited contact with groups of people within confined spaces reduce the transmission of SARS-CoV-2. In addition, the use of Face mask Reduces the amount of virus released by presymptomatic and asymptomatic individuals. So stay at home and stay safe.

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Martha Gallia, Associate Professor of Molecular Biology and Microbiology, Tufts University And Cima Camel Walla, Associate Professor, University of Pittsburgh

This article has been reissued from conversation Under Creative Commons license. Read Original work.

Image: Reuters