from march 8 to march 28 , the hospital admitted five patients in whom sars - cov infection was subsequently laboratory - confirmed .
patients 4 and 5 were believed to have contracted sars on a march 15 flight from hong kong to beijing .
healthcare workers caring for these patients were exposed during two periods . during march 814 ,
before specific infection - control precautions were implemented , 73 healthcare workers were exposed to patients 1 and 2 . during march 1528 ,
after specific precautions were implemented , an additional 150 healthcare workers were exposed to all five patients .
all healthcare workers who had contact with sars patients used personal protective equipment , including gown , gloves , n-95 respirators , disposable cap , and shoe covers .
healthcare workers exposed to sars patients or their environments were monitored for signs or symptoms of sars for 14 days after the last exposure .
healthcare workers who had high - risk exposures to sars were excluded from new duty assignments .
we considered performing any of the following to be a high - risk exposure : endotracheal intubation > 30 min , cardiopulmonary resuscitation > 30 min , pleurocentesis > 30 min , or bedside care ( such as chest care [ including percussion and postual drainage ] or feeding ) > 30 min . any healthcare worker in whom fever developed ( temperature >
a total of 223 healthcare workers exposed to sars patients were interviewed by one of two researchers with a structured questionnaire designed by the centers for disease control and prevention ( cdc ) , usa , and the center for disease control , taiwan .
the following data were recorded on uniform case - report sheets : extent of personal protective equipment use during exposure , type of exposure ( stay in the same room , direct patient contact , or exposure to respiratory droplets and secretions ) , disease phase of patients to whom they were exposed ( during incubation period , early fever , fever and cough , or intubation period ) , occurrence of fever ( > 38c ) , and respiratory or gastrointestinal symptoms after exposure .
proportional data were tested by using  or fisher exact test ( epiinfo 6 , cdc , atlanta , ga ) .
serum samples were collected twice from 206 healthcare workers during a 1-month period after the initial exposure to patients with sars , with a minimum interval between collections of 2 weeks .
serologic response to sars - cov was determined by using an indirect immunofluorescence assay ( ifa ) as described previously ( 5 ) and the immunochromatographic test ( ict , tyson bioresearch , inc , taiwan ) .
data obtained from 13 patients with severe sars , as defined by using cdc criteria ( 7 ) , showed that the sensitivity of the ict test was > 90% within 2 weeks of fever onset and 100% after 6 weeks .
data obtained from 51 cases of severe sars demonstrated that the sensitivity of either ifa or ict was 98% after 6 weeks ( 8) .
the table compares the extent of personal protective equipment use before and after implementing specific infection - control measures .
healthcare workers during the  after  period were substantially more likely than the  before  period to have used full personal protective equipment ( table ) .
five healthcare workers stayed in the same room with sars patients before and after implementation of specific infection - control measures . among 223 healthcare workers ,
178 had direct contract to sars patients or their environment , and 129 had exposure to respiratory droplets and secretion .
first serum samples were collected 12.4  5.4 days ( mean  standard deviation ) after initial exposure to sars patients .
none of the 73 healthcare workers exposed during the before period produced a positive result on serologic tests for sars .
this group included a physician who intubated patient 1 and wore two layers of surgical masks and used inline suction after intubation .
, he performed a 30-min chest sonogram on patient 2 in a negative - pressure isolation room and wore an n-95 respirator , double gloves , gown , disposable cap , and shoe covers . on the same day
, he helped intubate patient 2 while positioned approximately 3 feet from the patient s head . during this period ,
the physician recalled that he had not tried the mask on or confirmed that it was air - tight before entering the isolation room .
fever developed 4 days later in this physician , designated as patient 6 , and pneumonia developed 5 days after that . both virus culture and
polymerase chain reaction ( rt - pcr ) demonstrated sars - cov in the sputum .
immunoglobulin ( ig ) g against sars - cov determined by ifa was > 1:1,000 ( 5 ) .
after this experience , the infection - control team reemphasized the importance of fit - testing facemasks and recommended wearing a face shield when in close contact with sars patients .
sars did not develop in another physician who intubated patient 2 and four nurses who assisted the procedure in the same room .
in this study , a physician who intubated a patient with sars while following standard precautions did not become ill , but sars developed in another physician whose n-95 respirator was not properly fit - tested . a serologic response to sars - cov could not be demonstrated in 205 healthcare workers who spent time in the same room as or had direct contact with sars patients .
the major question that arises from this study is why 36 ( 50% ) healthcare workers who stayed in the same room with sars patients before the outbreak was recognized and who did not wear masks were not infected .
patient 2 wore a face mask when she visited the emergency room . the physician who intubated patient 1 was alert , wore two layers of surgical masks , and followed standard precautions .
inline suction was routinely performed at the hospital for intubated patients to prevent aerosol formation ; therefore , unprotected healthcare workers might not have been exposed to a sufficient amount of sars - cov to produce a systemic infection .
an alternate explanation could be that existing serologic assays are not sufficiently sensitive to identify subclinical infections .
this explanation is unlikely , however , because the tests we used have been shown to be highly sensitive and specific in patients with sars ( 5,8 ) , and 90% of convalescent - phase serum samples were collected > 30 days after exposure .
yet another explanation could be that sars - cov is attenuated by serial passage in humans .
this explanation is also unlikely since sars developed in the five index patients admitted to the hospital in the early phase of the epidemic and in one physician with a poorly fitting mask .
further , phylogenic tree analysis ( 9 ) indicates that patients 2 , 3 , and 6 were infected by strains related to the large outbreak in amoy gardens in hong kong ( 2 ) , and patients 4 and 5 were infected by strains related to a large hospital outbreak in taipei ( 10 ) .
a final explanation could be , simply , that the disease does not develop in all people exposed to the virus .
transmission of sars was limited initially at our hospital ( attack rate 0.4% ) when healthcare workers followed standard precautions or specific infection - control measures , including droplet and contact precautions . however , in later stages of the epidemic , sars was more likely to develop in healthcare workers , despite similar or higher levels of personal protective equipment use .
although one possible explanation for this could have been exposure to unrecognized sars patients , contamination of the environment leading to indirect contact transmission may have also played a role ( 11 ) . in conclusion , while sars - cov can spread rapidly in a nonimmune human population ( 13 ) , this study demonstrated infrequent transmission of sars to healthcare workers caring for the first five sars patients in taiwan , despite a number of unprotected exposures .
nonetheless , given that sars has , on other occasions , shown itself to be highly transmissible ( 13,10 ) , we still recommend strict precautions ( 13,1114 ) .
 this study found infrequent transmission of severe acute respiratory syndrome ( sars ) coronavirus to healthcare workers involved in the care of the first five case - patients in taiwan , despite a substantial number of unprotected exposures . nonetheless , given that sars has been highly transmissible on some occasions , we still recommend strict precautions . 
The Study
Conclusions