When medicine collides with emotion, a UCSF COVID expert reflects on his son's positive test results.

After a well-known San Francisco COVID expert posted an extraordinary story on Twitter on Saturday, the retweets, likes, and comments lit up for hours.

Dr. Bob Wachter, UCSF's chief of medicine, wrote, "I've been tweeting about COVID for nearly 2 years." "However, it became personal this week when my younger son, 28, received it."

What followed, in 25 tweets, revealed a kind of internal wrestling match within Wachter — an internal battle between the data-savvy physician who knew that a young, triple-vaccinated person would probably weather COVID just fine — and as of Sunday, that appeared to be the case — and the loving father who felt the pandemic's pain up close, perhaps for the first time.

Wachter described his son as generally healthy but overweight, putting him at "moderately high risk" for COVID, with his son's permission. Wachter said his son works in customer service in San Francisco's downtown area. He is cautious. He hides behind his mask. When omicron struck in December, his father advised him to switch from his two-ply cloth mask to the more conservative KN95.

"I was afraid he'd pick it up at work or on the bus," Wachter wrote. "However, that was not the case."

On Monday night, a fully vaccinated friend joined his son to watch a movie. "He woke up feeling awful" on Wednesday morning.

His son had a sore throat, a dry cough, and aching muscles. He was shivering.

Wachter tweeted, "I told him to stay home, drink fluids, and take Tylenol or Advil."

Since the coronavirus first appeared in the United States in early 2020, the doctor has been at the forefront of the COVID pandemic. He has established himself as a leader in public awareness of the disease, its treatment, and prevention. Wachter, an internal medicine expert, was named by Modern Healthcare Magazine in 2015 as "the most influential physician-executive in the United States."

Even he had trouble getting a COVID test for his son.

He wrote, "Local pharmacies were all out of rapid tests." "However, I did have one set stashed away."

He donned a gold-standard N95 mask, met his son outside, and inserted a swab into his nose.

His son had a negative test result.

The doctor said the negative result made him feel "a little reassured," but he wondered if it was one of the "false-negatives" he'd heard about with rapid tests.

His son, who was still sick, was skeptical. So he dialed the UCSF COVID hotline to schedule a PCR test, only to be told that there were no appointments available for four days.

Wachter went to the kitchen and made chicken soup. But, because he's Wachter, he also checked his son's oxygen levels (which were fine) and heart rate (which was "concerning" at 120 beats per minute).

He called his son at 9 a.m. the next morning, Thursday.

"No response."

That's when the physician father, who had told his son to call if his oxygen level fell below 95%, yielded to the father father.

"For a brief moment, I wondered if he'd made it through the night," Wachter tweeted.

He wrote, "My brain knows the chances of a fully vaxxed young person dying are near-zero." "Evidence-based medicine meets parental emotion," the battle within had already begun.

At 10 a.m., he tried his son again, and when he received no response, he went to his son's house and let himself in.

"Sleeping... and breathing," he discovered his son there.

His son's friend tested positive that morning, seemingly confirming his son's diagnosis. Another test, however, was required.

Wachter looked at reports this time that suggested swabbing your nose might not be enough. "Swabbing the throat AND nose" works better, he wrote.

"We did that: a good rub around his tonsils and tongue, followed by (same swab - a little gross) both nostrils."

They waited the customary 15 minutes, and the dreaded pink line appeared this time.

"My son had COVID, like millions of other young people," Wachter tweeted. "I felt a strange guilt for not protecting him — not entirely rational, but real."

"When it's your kid, you freak out a little," Wachter said, even though he knew his son would be fine.

After looking into his son's prognosis, using a risk calculator, considering treatments, and speaking with his son's doctor, physician dad relinquished control and let it go.

"Any lessons?" he tweeted as he neared the end of his story.

"First, thank God for vaccines!" the professor said in response to his own question. Yes, he had COVID, but his vaccination reduced his chances of developing a severe case, hospitalization, and death."

"False negative rapid tests in omicron are real, as are shortages of tests and meds," says the second lesson.

Then there's omicron's lesson: "Lower your guard & it'll pounce," he wrote, noting that the illness — and the anxiety — "are miserable."

"Should he have watched movies with his friend?" Wachter finally asked. And he responded to his own question.

"I believe so."

"Even low risk stuff - things that were safe last month - may now be risky," he wrote, "while Omi is surging." Given how quickly this storm could pass, it seems prudent to seek shelter."

Wachter returned to Twitter on Sunday with an update, saying, "Thanks, folks, for asking about my son." Today is better, though my throat is still bothering me. Many people are going through a lot worse." He expressed his gratitude for people's kindness. "Thank you to those who offered test kits; we got a few and are now all set."