Fig. 1

Exhaled breath particle concentrations and particle size distributions differed significantly between symptomatic and healthy patients. Particles in exhaled air were measured using an optical particle counter. A Particles per exhaled volumes (PEV) for patients with PCR-verified COVID-19 infection (COV-POS), patients with respiratory symptoms but with > 2 negative polymerase chain reaction (PCR) tests for COVID-19 (COV-NEG) and healthy controls (HCO) Data shown as individual values (black dots) with lower and upper boundary of boxplots representing 25th and 75th percentile. Statistical significance was tested with Kruskal–Wallis test with Dunn’s multiple hypothesis testing correction. B Relative particle size counts per particle size bin for COV-POS, COV-NEG and HCO. Data are shown as mean ± standard error of mean. Statistical significance was tested using ANOVA with Tukey’s multiple comparisons correction and significance values are shown between COV-POS and HCO. Statistical significance was defined as ****p < 0.0001, ***p < 0.001, **p < 0.01, *p < 0.05 and NS (p > 0.05)