How have lessons learned from the severe acute respiratory syndrome and H1N1 pandemics impacted infection control?

The pandemics of severe acute respiratory syndrome (SARS) and influenza H1N1 are recent memories that have heightened the sense of concerns by health care epidemiologists for rapid responses to new and emerging pathogens. There is always uncertainty initially about optimal infection control measures to implement, since the virulence, case reproduction rate, and transmission characteristics of the new respiratory agent are unclear.

Nevertheless, until the epidemiology and pathogenesis of a newly emerging respiratory pathogen are defined, the use of masks, gowns, and gloves, combined with assiduous hand hygiene and increased environmental disinfection are warranted. Some recent studies would suggest protecting the eyes and mucous membranes when taking care of patients with a novel respiratory pathogen and double gloving instead of wearing a set of single gloves.

What elements of these lessons are necessary for infection prevention and control?

In the face of a newly emerging respiratory pathogen, there are theoretical arguments for the use of N-95 masks over the standard surgical masks. These are based on the superior filtering capacity and fit tightness of the N-95 respirator. The early use of negative pressure rooms in a novel respiratory pandemic is also reasonable and ideal. The environment, including nursing stations, table tops, computer keys and mouse, patient bedside stands, etc., must be assumed to be contaminated at all times. Hand washing before and after each patient encounter and after touching the environment should be meticulously performed, and special efforts to avoid touching one’s face should be made.

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Surge capacity needs to be in place, and that usually means that more beds (including ICU beds) have to be available; the Emergency Department will need to implement an effective triage activity and may require additional medical and nursing support and space. In Mexico, an early lesson was the reconfiguration of the hospital with some sections devoted to patients likely to be infected with H1N1. Non-infected patients were segregated to another section to avoid cross transmission. A thoughtful aspect of planning surge capacity would be to define what increased thresholds of inpatients and outpatients would trigger a specific need for added medical and nursing personnel, support staff, and beds at various locations in the hospital. Then the question is, “where will the supply of medical personnel come from”?

There were some hospitals that quickly ran out of respirators, of oxygen and available medical expertise, and the increased availability of critical medical supplies needs to be kept in mind with an outbreak of respiratory infections.

In the recent H1N1 pandemic, public health authorities failed to have a clear message about the seriousness of the outbreak and needed precautions. There were differences of opinions about the use of the N-95 mask, with CDC favoring their use and the WHO and SHEA favoring the standard surgical mask. However, when the country ran out of the N-95 mask, it showed that recommendations made without considering the availability of specific equipment only increases skepticism for those in authority. Furthermore, when the vaccine that was promised was delivered late in the pandemic, confidence in the public health authorities was further eroded.

At other times the recommendations did not match the epidemiology; the CDC recommended that children and adults return to school or day-care and work, respectively, after one day of being afebrile even though children shed the virus for up to 3 weeks and adults for 5 days. This author thinks that although difficult, the public health authorities need to become clearer about the lexicon of uncertainty, what they know and don’t know about a pandemic.

What are the conclusions from clinical trials or meta-analyses regarding severe acute respiratory syndrome and H1N1 that guide infection control practice and policies?

Retrospective studies from Hong Kong during the SARS outbreak suggested that wearing a mask actually protected health care workers; specifically, paper masks were not effective, but both surgical masks and N-95 respirators were protective. In Canada, the initial failure to adhere strictly to infection control guidelines led to in-hospital transmission of SARS to patients and health care providers. In Mexico, the hospital environment was found to be contaminated as were the hands of health care providers.

What are the consequences of ignoring key concepts related to lessons learned from severe acute respiratory syndrome and H1N1?

Failure to adhere to infection control guidelines led to serious life-threatening infections among health care providers and patients during the SARS outbreak. In Mexico during the H1N1 pandemic, the emphasis on hand washing and avoidance of touching one’s face was thought to be highly effective in minimizing H1N1 infections among health care workers.

A summary of current controversies regarding the lessons learned from severe acute respiratory syndrome and H1N1.

The major infection control controversy with respect to influenza and debated strongly with the H1N1 pandemic in mind is the relative value of the N-95 vs. the standard surgical mask in preventing transmission of infection from patients to health care workers from patients. The unknown information includes the proportion of influenza transmissions that occurs from droplet nuclei (smaller than 10 microns across and thus reparable) vs. larger droplets that fall to the ground in 3 to 6 feet. In contrast to large droplets, droplet nuclei do not fall to the ground but instead stay aloft and move with air currents. Thus, transmission could occur hours after the infected person coughed and left the area.

If large droplets and droplet nuclei both contribute to transmission, what additional proportion of infections is acquired from the environment contaminated with the virus? The answers to these questions would guide a reasoned approach to control influenza; are N-95 respirators superior or only marginally better at preventing transmission in actual patient care? What degree of effort should be spent on cleaning the environment during an epidemic?

Overview of the important clinical trials, meta-analyses, case control studies, case series, and individual case reports related to infection control and lessons learned from SARS and H1N1.

SARS and H1N1 represent the newest respiratory pathogens that have caused global infections. Although SARS has subsided, H1N1 may remain as a seasonal pathogen, perhaps with minor antigenic drifts in its key surface protein spikes. More importantly, the H1N1 outbreak focused attention on controlling new influenza viral infections in general, the need for more rapid vaccine development perhaps through cell based rather than egg based techniques, and the need for rapid global distribution of effective antibiotics and vaccines.

The effectiveness of hand washing has been examined in SARS. In a review of 10 case-control studies focusing on SARS, Fung and Cairncross noted that nine of 10 showed protection in univariate analyses, and three showed protection in multivariate analyses. The disparity was ascribed to the small studies in general. The multivariate data showed a 76 to 93% protection of healthcare workers who washed their hands after each patient encounter and a 56% protection in general for health care workers who washed their hands at least 10 times a day.

A study from China also looked at risk factors for infection among health care workers. In their multivariate analysis, Chen and colleagues showed that the risk of acquiring SARS was 4.13 times greater for health care workers who wore one set of gloves vs. those who double gloved when taking care of patients. More data are needed, but this study supports early use of double gloves until the virulence and pathogenesis of a new agent are defined.

In a report from Toronto, Raboud and colleagues showed in a multivariate analysis that failure to protect the eyes/ mucous membranes from exposure to body fluids had an Odds Ratio of 7.34 for SARS infection (p = 0.001).

From a perspective of limiting nosocomial spread of SARS, the paper by Yu et al is interesting. In a multivariate model the authors showed that having a minimum distance between beds of less than or equal to 1 meter was a significant risk factor for transmission in the hospital – OR of 6.94 (0 = 0.008).

Controversies in detail.

The key controversy relates to personal protective equipment (PPE) for health care workers exposed to respiratory viruses. More work has been done in influenza to try to learn.


Wenzel, RP, Edmond,, MB. “Managing SARS Amidst Uncertainty”. N Eng J Med. vol. 348. 2003. pp. 1947-8.

Wenzel, RP, Edmond, MB. “Listening to SARS: Lessons for Infection Control”. Ann Int Med. vol. 139. 2003. pp. 592-3.

Wenzel, RP, Bearman, G, Edmond, MD. “Lessons from SARS: Implications for Infection Control”. Arch Med Res. vol. 36. 2005. pp. 610-6.

Wenzel, RP, Edmond, MB. “Preparing for 2009 H1N1 Influenza”. N Eng J Med. vol. 361. 2009. pp. 991-3.

Wenzel, RP. “What We Learned from H1N1's First Year”. Op-Ed. NY Times. April 13, 2010. pp. 23

Lee, SA, Grinshpun, SA, Reponen, T. “Respiratory performance offered by N-95 respirators and surgical masks: Human subject evaluation with NsCl aerosol representing bacterial and viral particle size range”. Ann Occupational Hyg. vol. 52. 2008. pp. 177-85.

Macias, AE, de la Torre, A, Moreno-Espinosa, S. “Controlling the novel A ( H1N1 ) influenza: don't touch your face !”. J Hosp Infect. vol. 73. 2009. pp. 280-1.

Seto, WH, Tsang, D, Yung, RWH. “Effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (SARS )”. Lancet. vol. 361. 2003. pp. 1519-22.

Varia, M, Wilson, S, Sarwal, s. “Investigation of a nosocomial outbreak of severe acute respiratory syndrome ( SARS ) in Toronto, Canada”. CMAJ. vol. 169. 2003. pp. 285-92.

Fung I, C-H, Cairncross. “Effectiveness of Handwashing in Preventing SARS: A Review”. Trop Med Internat Health. vol. 11. 2006. pp. 1749-58.

Chen, W-Q, Ling, W-H, Lu, C-Y. “Which preventive measures might protect health care workers from SARS?”. BMC Public Health. vol. 9. 2009.

Raboud, J, Shigayeva, A, Mc Greer, A. “Risk Factors for SARS Transmission from Patients Requiring Intubation: A multicentre Investigation in Toronto, Canada. ( 2010)”. PLoS ONE. vol. 5.

Yu, IT, Xie, ZH, Tsoi, KK. “Why did outbreaks of severe acute respiratory syndrome occur in some hospital wards but not in others “. Clin Infect Dis. vol. 44. 2007. pp. 1017-25.