Clinical and epidemiological predictors of transmission in Severe Acute Respiratory Syndrome (SARS).
BACKGROUND
Only a minority of probable SARS cases caused transmission. We assess if any epidemiological or clinical factors in SARS index patients were associated with increased probability of transmission.


METHODS
We used epidemiological and clinical data on probable SARS patients admitted to Tan Tock Seng Hospital. Using a case-control approach, index patients who had probable SARS who subsequently transmitted the disease to at least one other patient were analysed as "cases" against patients with no transmission as "controls", using multivariate logistic regression analysis.


RESULTS
98 index patients were available for analysis (22 with transmission, 76 with no transmission). Covariates positively associated with transmission in univariate analysis at p < 0.05 included delay to isolation (Day 7 of illness or later), admission to a non-isolation facility, pre-existing chronic respiratory disease and immunosuppressive disease, need for oxygen, shortness of breath, vomiting, and higher lactate dehydrogenase levels and higher neutrophil counts. In the multivariate analysis, only three factors were significant: delay to isolation, admission to a non-isolation facility and higher lactate dehydrogenase levels of >650 IU/L (OR 6.4, 23.8 and 4.7 respectively).


CONCLUSIONS
Clinical and epidemiological factors can help us to explain why transmission was observed in some instances but not in others.
Chen
Mark I C
MI
Clinical Epidemiology, Communicable Disease Centre, Tan Tock Seng Hospital, Jalan Tan Tock Seng, Singapore. mark.chen@lshtm.ac.uk
Chow
Angela L P
AL
Earnest
Arul
A
Leong
Hoe Nam
HN
Leo
Yee Sin
YS
D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000097:blood; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010356:Patient Isolation; D012307:Risk Factors; D045169:Severe Acute Respiratory Syndrome / Q000175:diagnosis / Q000453:epidemiology* / Q000635:transmission*; D012846:Singapore / Q000453:epidemiology
D007770:L-Lactate Dehydrogenase