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Make the noise of “Kruuua” from the throat to clear saliva from deep throat.

It was step No. 5 of the coronavirus test guidelines, accompanied by a photograph of a man wearing a surgical mask and holding a plastic vial, the word ‘Kruuua’ splashed across the image in white text.

I mustered my strength, took a breath, and cleared my throat as hard as I could, sounding like a weak espresso machine, and then spat into the small plastic cup in my hand.

My contribution to an at-home coronavirus test was complete.

At the end of April, I felt a tickle in my throat. By the next evening, the pain made it difficult to swallow food. I knew that a sore throat was one of the symptoms of COVID-19, and I knew that Hong Kong, where I live, had not reported a locally-transmitted coronavirus infection for almost two weeks. Besides the worry that I might be sick and could have passed it on to others, I could think of few things worse than being the one to ruin that streak.

But I had no fever and no other coronavirus symptoms—dry cough, fatigue, or shortness of breath. I also recalled that a woman I’d interviewed for a story in April, who’d recovered from COVID-19, described a pain “very low down in the throat” that felt unlike any sore throat she’d had before. Mine didn’t feel like that.

Still: the streak. The next morning I made an appointment with my doctor. I described my symptoms over the phone and confirmed that I had no recent travel history or contact with a confirmed case.

To my relief, she diagnosed me with tonsillitis, and prescribed a course of antibiotics. But then she asked if I wanted to take a coronavirus test.

For me, the administration of a diagnostic coronavirus test conjured images of patients, heads tilted back, with hazmat-suited medical workers shoving giant Q-tips up their noses or down their throats. One person likened the swab test to “being stabbed in the brain.”

“Not something I want to do every day, I can tell you that,” U.S. President Donald Trump has said of his swab experience. “Nothing pleasant about it.”

My doctor must have seen the fear in my eyes, because she added that it would be a take-home test. There would be no swab, only spit.

I went home with a doggie bag of tools: written instructions, the specimen collection bottle—a small plastic screw-cap cup—and two sealable plastic specimen carrier bags, labeled ‘DANGER OF INFECTION’ in capital letters and the spiky trefoil biohazard symbol in yellow and black, with ‘BIOHAZARD’ emblazoned underneath for good measure. (Subtlety is not a virtue in a global pandemic.)

After spitting into the cup in the next morning—before eating, drinking, or brushing my teeth, as instructed—I twisted the lid shut and sealed it in the plastic bags. The sample was labeled with my name, gender, birth date, and Hong Kong identity card number.

A friend dropped off the sample at the clinic that same day—I was advised to stay home, since I might have coronavirus—and the clinic sent it to the Hong Kong public health lab that processes the tests. The following afternoon, the clinic emailed me the results. (They’d called first, but I missed it.) SARS-CoV-2 RNA had not been detected in my sample. I had tested negative, and Hong Kong’s streak remained intact.

Spit vs. swab

The saliva test like the one I took is available in Hong Kong at government outpatient clinics and some private clinics, including the one I went to. All samples are sent to a public hospital lab that conducts at least 2,000 tests per day.

Hong Kong is one of the few places in the world that offers the spitting method to test for the coronavirus, said Ben Cowling, an epidemiologist at the University of Hong Kong.

Most countries use the more common swab test, which is also available in Hong Kong, and is the “standard procedure” to test whether people have viral infections, Cowling said.

Cowling said Hong Kong developed the saliva test because health workers were “reluctant” to carry out swab tests for fear of getting infected during the process that requires close interaction with a potentially infectious patient. In early February, public hospital union workers went on strike for various demands, including more face masks—there was a shortage in Hong Kong at that time—and protective gear for medical staff.

The swab test must be carried out by a health professional, who inserts the six-inch swab into the patient’s nose or throat to reach the nasopharynx (the cavity between nose and mouth) and swirls the swab around for 15 seconds to collect enough material.

The swab and saliva tests use the same process—the polymerase chain reaction (PCR) method—to detect the RNA of SARS-CoV-2, the coronavirus strain that causes COVID-19.

The saliva test largely eliminates the risks the swab test poses to health care workers and is far less invasive. The one potential downside is that it may have a slightly lower sensitivity than the swab test, Cowling said, but “it’s still an acceptable test to do for everybody.”

The nasopharynx is typically the best area to sample for respiratory diseases. People who have mild symptoms or are in the early stage of infection might have a concentration of virus RNA in the nasopharynx that a saliva test might miss. (The ‘KRUUUA’ is meant to bring up that back-of-throat sputum.) But an April 22 study by researchers at the Yale School of Public Health said the saliva tests were a “viable and more sensitive alternative” to swabbing for coronavirus.

Supply shortages

Since April 8, every single passenger flying into Hong Kong International Airport must take a deep throat saliva test and test negative for COVID-19 before they can enter the city. From the airport, travelers are shuttled to the nearby Asia World-Expo, a major concert venue repurposed as a “temporary specimen collection centre” for coronavirus testing.

Some people have raised concerns about giving their biodata and other personal information to the government. Hong Kong’s health ministry disposes of the saliva samples according to lab protocols, Bloomberg News reported, but the ministry did not specify what the protocols were.

The at-home spit test could prove helpful for places like the U.S., where there is an ongoing nationwide lag in coronavirus testing, in part due to swab supply shortages across the country. The at-home component could also ease the burden on the U.S.’s overwhelmed medical system—people could mail in their tests, instead of traveling to a clinic or hospital where workers need to don fresh personal protective equipment, also in short supply, for each patient they see.

A saliva test developed by a Rutgers University lab is now available in some parts of New Jersey, the first place in the U.S. to offer such a test.

For me, the at-home test provided pain-free peace of mind that I was not infected with coronavirus. Meanwhile, my tonsillitis has cleared up, and May 8 marked the 19th straight day with zero new local infections in Hong Kong.