Volume 11, Number 7—July 2005
Dispatch
Asymptomatic SARS Coronavirus Infection among Healthcare Workers, Singapore
Annelies Wilder-Smith*
, Monica D. Teleman*, Bee H. Heng†, Arul Earnest*, Ai E. Ling‡, and Yee S. Leo*
, Monica D. Teleman*, Bee H. Heng†, Arul Earnest*, Ai E. Ling‡, and Yee S. Leo*
Table 2
Univariate analysis of risk factors associated with asymptomatic versus pneumonic SARS*†
| Variable | Asymptomatic SARS | Pneumonic SARS | p value‡ | Controls | p value§ |
|---|---|---|---|---|---|
| Median antibody titer (range) | 1: 4,000 (1:400–1:6,400) | 1:6,400 (1:1,600–1:6,400) | 0.013¶ | NA | NA |
| Mean age (SD) | 26.5 (4.3) | 29.6 (9.2) | 0.706¶ | 33.7 (11.5) | 0.098# |
| Females (%) | 6 (100) | 32 (86) | >0.999 | 49 (94) | 0.321 |
| No. who used masks (%) | 3 (50) | 3 (8) | 0.025 | 21 (40) | 0.002 |
| No. who used gloves (%) | 1 (17) | 10 (26) | >0.999 | 24 (46) | 0.090 |
| No. who washed hands (%) | 4 (67) | 29 (76) | 0.63 | 47 (90) | 0.110 |
| No. who were close to a SARS patient (≤3 ft), % | 5 (83) | 35 (92) | 0.456 | 48 (92) | 0.747 |
| Median contact time in minutes (range) | 67.5 (10–360) | 60 (10–480) | 0.863¶ | 30 (10–960) | 0.879# |
*SARS, severe acute respiratory syndrome; NA, not available.
†SARS serology–negative asymptomatic controls added for comparison. All p values from Fisher exact test or chi-square test, unless otherwise stated.
‡p value for comparing asymptomatic versus pneumonic SARS.
§p value for comparing any 2 pairs in the 3 groups. For multiple comparisons, level of significance was set at 0.017 using the Bonferroni method.
¶p values from Mann-Whitney test.
#p values from Kruskal-Wallis test.
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