Table 3 Factors associated with virus positivity on masks surface

 Hospital A

Ref^a

 Hospital B

0.22 (0.03–1.75)

 Hospital C

0.25 (0.05–1.18)

 Internal medicine department

Ref

 Respiratory department

0.04 (0.01–0.34)^d

 Pediatrics department

0.12 (0.01–0.97)^d

 Male

Ref

 Female

0.57 (0.16–1.97)

 Doctor

Ref

 Nurse

0.97 (0.33–2.82)

  ≤ 30 years

Ref

 31–40 years

0.57 (0.15–2.11)

  ≥ 41 years

1.06 (0.28–3.98)

  ≤ 6 h

Ref

  > 6 h

7.9 (1.01–61.99)^d

  ≤ 25 cases

Ref

  > 25 cases

5.02 (1.35–18.60)^d

 Used continuously

Ref

 Used continuously except breaks^b

0.65 (0.19–2.22)

 Used only during patients encounters

0.10 (0.01–2.12)

 Used only high-risk patient encounters

3.02 (0.43–21.44)

 No

Ref

 Yes

2.24 (0.76–6.55)

 No

Ref

 Yes

0.59 (0.12–2.94)