Risk Factors for SARS Transmission from Patients Requiring Intubation: A Multicentre Investigation in Toronto, Canada

Abstract

BackgroundIn the 2003 Toronto SARS outbreak, SARS-CoV was transmitted in hospitals despite adherence to infection control procedures. Considerable controversy resulted regarding which procedures and behaviours were associated with the greatest risk of SARS-CoV transmission.MethodsA retrospective cohort study was conducted to identify risk factors for transmission of SARS-CoV during intubation from laboratory confirmed SARS patients to HCWs involved in their care. All SARS patients requiring intubation during the Toronto outbreak were identified. All HCWs who provided care to intubated SARS patients during treatment or transportation and who entered a patient room or had direct patient contact from 24 hours before to 4 hours after intubation were eligible for this study. Data was collected on patients by chart review and on HCWs by interviewer-administered questionnaire. Generalized estimating equation (GEE) logistic regression models and classification and regression trees (CART) were used to identify risk factors for SARS transmission.Results45 laboratory-confirmed intubated SARS patients were identified. Of the 697 HCWs involved in their care, 624 (90%) participated in the study. SARS-CoV was transmitted to 26 HCWs from 7 patients; 21 HCWs were infected by 3 patients. In multivariate GEE logistic regression models, presence in the room during fiberoptic intubation (OR = 2.79, p = .004) or ECG (OR = 3.52, p = .002), unprotected eye contact with secretions (OR = 7.34, p = .001), patient APACHE II score ≥20 (OR = 17.05, p = .009) and patient Pa02/Fi02 ratio ≤59 (OR = 8.65, p = .001) were associated with increased risk of transmission of SARS-CoV. In CART analyses, the four covariates which explained the greatest amount of variation in SARS-CoV transmission were covariates representing individual patients.ConclusionClose contact with the airway of severely ill patients and failure of infection control practices to prevent exposure to respiratory secretions were associated with transmission of SARS-CoV. Rates of transmission of SARS-CoV varied widely among patients.

Aerosol Transmission of Infectious Disease

“…1 Specific medical procedures that aerosolize respiratory secretions were associated with outbreaks among health care workers, including resuscitation, positive airway pressure ventilation, and endotracheal intubation. [36][37][38][39][40][41] These medical procedures also require workers to be in proximity to patients, so it is not possible to retrospectively attribute exposures to specific routes of transmission. No experimental studies in humans have demonstrated transmission of SARS by aerosol or any other route.…”

Influenza Virus Infectivity and Virulence following Ocular-Only Aerosol Inoculation of Ferrets

“…CDC guidelines recommend ocular protection in conjunction with respiratory protection during laboratory or occupational exposure to respiratory viruses (6), but these recommendations are not stringently observed, and numerous cases of ocular complications have been reported for individuals wearing respiratory protection in the absence of eye protection (1,7,8). Despite this, the relative risk of acquiring a respiratory infection via ocular exposure has not been examined.…”

Infection prevention and control measures for acute respiratory infections in healthcare settings: an update

“…No other procedures emerged with such a clear association. There were 2 studies reported for non-invasive ventilation which demonstrated a pooled OR of 3.1, but they were low quality studies in which the association in one was not statistically significant [20] and the other was also not significant after multivariate analysis [21]. On the basis of the review, the WHO has made a strong recommendation in the recently revised ARI guideline that identifies intubation for special attention as a procedure associated with risk of transmission of respiratory viruses [8] (see recommendations 6 and 7 in Table 2).…”