According to a new study, traces of the SARS-CoV-2 coronavirus that causes COVID-19 can be detected in microscopically small fluid droplets exhaled during a very short time span.

Researchers from the University of Gothenburg found that aerosol particles with the ribonucleic acid (RNA) virus can be found early in the course of COVID-19. The study was published in the journal Influenza and Other Respiratory Viruses.New research demonstrated that a few breaths are sufficient for detecting traces of viruses in small fluid droplets. This immediately leads to conjecture about possibly replacing unpleasant nasal swabs tests with convenient and easy breath tests.

Emilia Viklund, a doctoral student in occupational and environmental medicine and lead author of the study said, "We show that aerosol particles with the ribonucleic acid (RNA) virus can be found early in the course of COVID-19.

The particles we can detect are very small-less than five micrometres in diameter and we have here managed to capture particles with RNA virus in just a few breaths." In an initial small study involving only 10 subjects conducted in the autumn of 2020, only one of the samples was positive. The researchers believed this resulted from conducting measurements too late in the course of the disease.

In collaboration with Sahlgrenska University Hospital, which allowed parallel measurement in connection with employees taking polymerase chain reaction (PCR) tests on the hospital grounds, the study eventually evolved to include more subjects in an earlier stage of the disease. These measurements were conducted in the spring of 2021 on medical professionals who had just submitted positive PCR samples for COVID-19. Three different techniques were used to collect the samples.

They were 20 normal breaths technique in which study subjects briefly hold their breath after a very deep exhalation and a technique in which the study subject coughed three times into the instrument.

The research showed that coughing generated the most positive breath samples collected with PExA (8 of 25) which was followed by deep breathing (3 of 25) and regular breathing (2 of 25). Two positive aerosol samples from normal respiration were also generated when collected with the instrument Breath Explore, although these came from individuals who were separate from the PExA findings with normal respiration.

"The quantity of aerosol particles we needed for the test was about one 10-millionth of the amount from nasal swab samples needed to detect viral RNA in regular respiration with PCR analysis," said Anna-Carin Olin.

"The findings from the deep-breathing manoeuvre came as a surprise. The amount of sample is minute. Fluid droplets that one exhales after deep breathing form largely in the small airways, where it is known that the virus can cause great damage. As a result, it would be exciting to further study the findings in the exhaled air in relation to disease progression," added Olin. The Alpha viral variant dominated when surveys were conducted, which caused the infection that often extended farther down into the lungs compared with the now dominant Omicron variant.