1 table omitted
Infections among health-care workers (HCWs) have been a common feature
of severe acute respiratory syndrome (SARS) since its emergence. The majority
of these infections have occurred in locations where infection-control precautions
either had not been instituted or had been instituted but were not followed.
Recommended infection-control precautions include the use of negative-pressure
isolation rooms where available; N95 or higher level of respiratory protection;
gloves, gowns, and eye protection; and careful hand hygiene. This report summarizes
a cluster of SARS cases among HCWs in a hospital that occurred despite apparent
compliance with recommended infection-control precautions.1
The index patient was a Canadian family physician aged 54 years with
a history of hyperlipidemia, hypertension, and noninsulin-dependent diabetes
controlled on oral medications. During April 1-2, 2003, he examined three
patients who were family members involved in a community cluster of SARS in
Toronto, Ontario.2 No infection-control
precautions were used. On April 4, he had fever, myalgia, headache, mild diarrhea,
and a dry cough; on medical evaluation, he had a clear chest radiograph, but
he continued to feel ill during home isolation. On April 8, he was reevaluated
and found to have a left upper-lobe infiltrate on a repeat chest radiograph;
he was admitted to the SARS ward of hospital A. During the next several days,
he remained febrile with increasing cough, although his diarrhea resolved.
On April 12, the patient's temperature was 104.7°F (40.4°C), his chest
radiograph showed worsening pneumonia, and he required supplemental oxygen
for hypoxia. He was treated with ipratropium bromide and albuterol sulfate
by metered dose inhaler, intravenous (IV) ribavirin, and steroids. On April
12, he had a nearly constant cough and was assessed for transfer to the intensive
care unit (ICU). On April 13, the patient was transported to the ICU in a
wheelchair on 100% oxygen through nonrebreather face mask. Soon after his
arrival in the ICU, his measured oxygen saturation decreased to 60%, and he
was placed on positive pressure ventilation through face mask (BiPAP). Because
of severe cough and agitation, he removed the mask repeatedly despite administration
of IV sedation. After an approximately 2-hour attempt to provide oxygen through
BiPAP, the patient was intubated. During intubation, he had copious frothy
secretions that later obstructed the ventilator tubing, requiring disconnection
and drainage. Once supported with mechanical ventilation, the patient was
sedated further by using IV midazolam/morphine sulfate.
Later that evening, the patient was switched from assist-control ventilation
to high-frequency oscillatory ventilation (HFOV) because of continued inadequate
oxygenation. At this point, the patient's condition stabilized, and he was
maintained on HFOV for 7 days, after which he was switched back to assist-control
mode. As of May 14, the patient remained in critical condition. Both a sputum
sample collected from the patient on April 13 and a stool sample collected
on May 5 were positive for the SARS-associated coronavirus (SARS-CoV) by polymerase
During April 15-21, nine HCWs who had cared for this patient around
the time he was intubated had illnesses consistent with the World Health Organization
case definition for suspect or probable SARS3;
another two HCWs had symptoms that were not consisent with the case definition.
Six of these 11 HCWs had been present during the intubation procedure. Interviews
with affected HCWs indicated that they all had worn the recommended personal
protective equipment each time they entered the patient's room, including
gown, gloves, PCM2000™ duckbill masks (Kimberly Clark Health Care, Roswell,
Georgia), and goggles with or without an overlying face shield.
The room in which the intubation took place was at negative pressure
to the hallway, and all air was vented to the outside after high-efficiency
particulate air filtration; however, no anteroom was available, and removal
of personal protective equipment took place in a staged manner both inside
and outside the room, with the door kept closed between each entry and exit.
Understanding of the correct order to remove personal protective equipment
(PPE) (i.e., gloves first followed by mask and goggles) varied among HCWs.
Masks worn by HCWs inside ICU rooms and halls were changed on leaving
each patient's room; however, no formal respiratory protection program existed
at the hospital, and individual workers had not been fit tested. In addition,
the primary nurse for the patient had a small beard and reported that his
mask did not fit well. Although he wore both a PCM2000™ duckbill mask
and a surgical mask with face shield, he sometimes could feel air entering
around the sides of his mask.
M Ofner, Div of Blood Safety, Nosocomial and Occupational Infections;
M Lem, S Sarwal, Field Epidemiology Training Program, Health Canada; M Vearncombe,
A Simor, Sunnybrook and Women's College Health Sciences Centre, Toronto, Ontario,
Canada. SARS Investigative Team, CDC.
Transmission of SARS appears to result primarily from direct patient
contact or contact with large respiratory droplets in the close vicinity of
an infected person. Despite apparent limited modes of transmission, SARS has
been known to spread extensively among HCWs in various settings. For example,
among 138 cases of secondary and tertiary spread in Hong Kong, 85 (62%) occurred
among HCWs4; among 144 cases in Toronto,
73 (51%) were HCWs.5 SARS infection of HCWs
might be related to increased contact with respiratory secretions, contact
with patients during a more contagious phase of critical illness, contact
with particular patients at increased likelihood of spreading SARS (i.e.,
super spreaders), or exposure to aerosol-generating patient-care procedures.6
Health Canada and CDC are aware of several unpublished reports of SARS
clusters among unprotected HCWs involved with intubation, both in Canada and
outside North America. The cluster described in this report might be unique,
as HCWs appear to have followed infection-control precautions recommended
by Health Canada. The Health Canada recommendations, although similar to those
of CDC, differ from CDC guidelines with respect to respiratory protection.
CDC guidelines specify use of respirators approved by the National Institute
for Occupational Safety and Health (NIOSH) rated at an N95 level of protection
or greater.7 Health Canada recommends use
of "N95 equivalent" respirators.8 The respirators
used in hospital A, although compliant with Canadian public health recommendations,
were not NIOSH-approved. In addition, at the time these exposures occurred,
fit testing was not recommended by Canadian public health authorities; such
testing has been mandated in the United States since 1972.
Endotracheal intubation might cause an awake or a semiconcious patient
to cough and often necessitates open suctioning of respiratory secretions.
In addition, other potentially aerosol-generating procedures were performed
on this patient, including BiPAP, during which air might be forced out around
the face mask and thereby aerosolize secretions, and HFOV, during which exhaust
from the ventilator tubing is more likely to escape without passing through
an antibacterial/antiviral filter. The patient also was in his second week
of illness with clinical deterioration and severe cough, possibly explaining
why HCWs who were exposed to the patient only before his transfer to the ICU
became infected, as the viral loads of patients at this stage of illness appear
Direct contact with the patient or contact with an environment contaminated
by large respiratory droplets might have led to HCWs infecting themselves
as they removed their PPE. For example, HCWs have been known to spread other
nosocomial pathogens from patient to patient despite the use of barrier precautions;
even in the best of circumstances, correct use of PPE might be suboptimal.
If contact or droplet spread alone were responsible for this cluster, a lapse
in technique would be required on the part of each infected HCW. Many HCWs
apparently lacked a clear understanding of how best to remove PPE without
contaminating themselves. Alternatively, aerosolizing procedures or the patient's
own cough might have led to airborne spread, and either the level of respiratory
protection used or the manner in which it was used did not prevent transmission.
This cluster is part of a larger number of cases in HCWs in hospitals
in the greater Toronto area who have become infected while caring for SARS
patients since directives for contact, droplet, and airborne precautions were
instituted at the provincial level on March 28.1 Further
investigation is necessary to determine factors associated with transmission
despite the apparent use of recommended infection-control precautions.
HCWs caring for SARS patients should be properly trained in the correct
use and removal of PPE and reminded of the importance of hand hygiene. Patients
who are experiencing rapid clinical progression with severe cough during their
second week of illness should be considered particularly infectious. Procedures
that might generate aerosols (e.g., nebulized medications, BiPAP, or HFOV)
should be avoided if possible. When intubation is necessary, measures should
be taken to reduce unnecessary exposure to HCWs, including reducing the number
of HCWs present and adequately sedating or paralyzing the patient to reduce
cough. Updated interim infection control precautions for aerosol-generating
procedures on patients who have SARS are under development and will be available
from CDC at http://www.cdc.gov/ncidod/sars/ic.htm.
Cluster of Severe Acute Respiratory Syndrome Cases Among Protected Health-Care Workers—Toronto, Canada, April 2003. JAMA. 2003;289(21):2788–2789. doi:10.1001/jama.289.21.2788
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