As the new coronavirus, which is responsible for the disease COVID-19, spreads worldwide, so too has viral advice for combating the pandemic.

One frequently copied and pasted bit of text that has gone viral on Facebook, Twitter, and WhatsApp suggests a simple self-check for coronavirus infection, usually attributed to “Taiwan Experts,” “Stanford University,” or “Stanford Hospital Board,” among others:

The new Coronavirus may not show signs of infection for many days. How can you know if you are infected? By the time you have fever and/or cough and go to the hospital, the lung is usually 50% fibrosis. Taiwan experts provide a simple self-check that we can do every morning: Take a deep breath and hold it for more than 10 seconds. If you do this successfully without coughing, without discomfort, stiffness or tightness, there is no fibrosis in the lungs; it basically indicates no infection. In critical times, please self-check every morning in an environment with clean air.

Stanford Health Care, for their part, explicitly stated they had nothing to do with the email:

A widely distributed email about COVID-19 that is attributed to a “Stanford Hospital board member” contains inaccurate information. It did not come from Stanford Medicine.

The viral text is often combined with other frequently recurring coronavirus claims including a paragraph attributed to “serious excellent advice by Japanese doctors” about keeping your throat moist, and a set of recommendations that begins with a claim about differentiating between a cold and COVID-19. Snopes addressed the “serious excellent advice” here, and addressed the list of tips that begin with a purported way to diagnose a cold versus COVID-19 here. This article deals only with the “self-check” claim attributed to Taiwan experts, which is flawed for several reasons.

The “simple self-check” hinges on two central and unsupported assertions: First, that early COVID-19 infections include as a symptom a condition known as pulmonary fibrosis; and second, that the ability to hold your breath for 10 seconds is an accurate indicator of fibrosis. Neither is the case.

Pulmonary Fibrosis Is Not a Symptom of COVID-19

Fibrosis occurs when excess connective tissue is deposited in the lungs in response to scarring or other factors. This excess of tissue can severely reduce the ability of lungs to bring oxygen to the body. To date, no major health agency has listed fibrosis as a symptom of COVID-19 at any stage in its progression. It is not listed as a symptom in the Centers for Disease Control and Prevention’s (CDC) “Clinical Guidance for Management of Patients with Confirmed Coronavirus Disease,” nor is it listed as a symptom in the World Health Organization’s joint report with China on the progression and spread of the disease.

While serious cases of COVID-19 usually involve pneumonia, which can cause scarring damage to the lungs, such damage would necessarily come after one showed obvious symptoms of pneumonia. The “self-check,” even if it had any diagnostic power at all, illogically implies damage to the lungs would precede other symptoms including coughing, even though it is the coughing that would be responsible for any respiratory damage in the first place.

Holding Your Breath Is Not a Valid Test for Pulmonary Fibrosis

The viral claim asserts that if you can hold your breath for more than 10 seconds “without discomfort, stiffness or tightness, there is no fibrosis in the lungs” and that this “basically indicates no infection.”

While holding your breath is likely harder if your lung capacity is reduced, there is no scientific support for the notion that holding your breath for 10 seconds indicates a clean bill of health, nor is there support for the implied assertion that the only reason holding your breath for 10 seconds would be hard is because COVID-19 caused pulmonary fibrosis. Several factors can reduce lung function, including allergies, asthma, chronic conditions, and infections. As such, there are multiple forms of respiratory tests that doctors perform on lungs to identify problems. None of them involves one’s ability to hold their breath for 10 seconds.

Because holding your breath is not a valid test for fibrosis, and because fibrosis is not a symptom of COVID-19, we rank this advice from “Taiwan experts” as “False.”