The amount of virus in saliva helps predict the future of covid patients

The covid appeared a year ago in the world being unpredictable.

Most of the patients had mild symptoms, but 15% needed oxygen and another 5% ended up in the ICU, if there was a gap.

In 1% of those affected, the infection ran out of control and ended with death, according to data from the first wave in Spain.

After a year of combat, the scientific community is learning to anticipate the movements of the virus.

The latest advance comes from the laboratory of immunologist Akiko Iwasaki, at Yale University (USA).

Their preliminary results suggest that the amount of virus in saliva is used to predict the outcome of the disease.

"The viral load in saliva in the first moments is correlated with the severity of the disease and with mortality," says Iwasaki's team, who has exhaustively analyzed 154 patients with covid at the university hospital in the city of New Haven.

Their data shows that the levels progressively increase from a minimum in mild patients to a maximum in seriously ill patients and in people who have died from covid.

The higher viral load in saliva is associated with known risk factors, such as advanced age, male sex, cancer, heart failure, hypertension, and chronic lung diseases.

"If we took saliva samples and analyzed the viral load - especially at the beginning of the infection, when the person arrives at the hospital - it could help doctors a lot to predict the patient's prognosis and choose the treatments," says Spanish microbiologist Arnau Casanovas, who has participated in the new study, still has a draft pending revision for publication in a specialized journal.

Casanovas, after seven years at Yale University, joined the American biotech Tangen Biosciences in August, dedicated to designing new diagnostic methods.

The team led by Iwasaki argues that saliva helps predict disease progression much better than samples taken with a nasopharyngeal swab, the now popular cotton swab inserted through the nose.

One of their hypotheses is that the nasopharyngeal culture only reflects the multiplication of the virus in the upper respiratory tract, while saliva also shows the situation in the lungs.

The mucociliary system - a defense mechanism to expel germs - would carry coronaviruses from the lower respiratory tract to the mouth.

Research shows that the higher viral load in saliva is also associated with a higher amount of biomarkers in the blood of the inflammatory reaction characteristic of severe COVID cases.

That higher viral load, on the contrary, is linked to lower levels of platelets, white blood cells and specific antibodies against the coronavirus.

Elisabet Pujadas, a Spanish pathologist and researcher at the Icahn School of Medicine at Mount Sinai Hospital in New York, applauds the new study, in which she has not participated.

"It brings a valuable perspective: that saliva may have a greater value than previously thought for diagnosis and prognosis," he says.

The Pujadas team already published in August the relationship between the highest viral load analyzed in nasopharyngeal samples and mortality from covid.

"It is possible that saliva may better reflect lower respiratory tract infection," he says.

"Saliva may have a greater value than previously thought for diagnosis and prognosis," says pathologist Elisabet Pujadas

Pujadas, who has been working in the US for more than 15 years, stresses that the new analysis only includes 154 patients, so it would "be premature" to conclude that saliva should now be used instead of nasopharyngeal samples.

"However, these promising results justify more resources being devoted to collecting and studying saliva samples," he adds.

For Pujadas, the main lesson is that you do not have to classify covid patients with a simple positive or negative.

You have to measure your viral load.

“For certain viruses, such as HIV, the quality standard is viral load, because years of research have shown that it has important implications for patient risk and affects our treatment strategy.

This should also be the case with covid ”, says Pujadas.

Iwasaki, Casanovas, and other colleagues published a study in September that suggested the potential of saliva to diagnose new coronavirus infections.

A systematic review of 37 investigations has just shown that saliva samples can replace nasopharyngeal swabs to diagnose covid, with the same precision and lower price.

“We have been saying for quite some time that it would be better to use saliva as a priority sample.

It is much easier to collect saliva than a nasopharyngeal swab.

You don't need a nursing staff.

Each person can spit at home in a small boat.

And you avoid the risk by taking the sample with the swab, because sometimes people sneeze or cough and aerosols are generated ”, reasons Casanovas.

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