Initial viral load and the outcomes of SARS.
BACKGROUND
Severe acute respiratory syndrome (SARS) is caused by a novel coronavirus. It may progress to respiratory failure, and a significant proportion of patients die. Preliminary data suggest that a high viral load of the SARS coronavirus is associated with adverse outcomes in the intensive care unit, but the relation of viral load to survival is unclear.


METHODS
We prospectively studied an inception cohort of 133 patients with virologically confirmed SARS who were admitted to 2 general acute care hospitals in Hong Kong from Mar. 24 to May 4, 2003. The patients were followed until death or for a minimum of 90 days. We used Cox proportional hazard modelling to analyze potential predictors of survival recorded at the time of presentation, including viral load from nasopharyngeal specimens (measured by quantitative reverse transcriptase polymerase chain reaction [PCR] of the SARS-associated coronavirus).


RESULTS
Thirty-two patients (24.1%) met the criteria for acute respiratory distress syndrome, and 24 patients (18.0%) died. The following baseline factors were independently associated with worse survival: older age (61-80 years) (adjusted hazard ratio [HR] 5.24, 95% confidence interval [CI] 2.03-13.53), presence of an active comorbid condition (adjusted HR 3.36, 95% CI 1.44-7.82) and higher initial viral load of SARS coronavirus, according to quantitative PCR of nasopharyngeal specimens (adjusted HR 1.21 per log10 increase in number of RNA copies per millilitre, 95% CI 1.06-1.39).


CONCLUSIONS
We found preliminary evidence that higher initial viral load is independently associated with worse prognosis in SARS. Mortality data for patients with SARS should be interpreted in light of age, comorbidity and viral load. These considerations will be important in future studies of SARS.
Chu
Chung-Ming
CM
Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, China.
Poon
Leo L M
LL
Cheng
Vincent C C
VC
Chan
Kin-Sang
KS
Hung
Ivan F N
IF
Wong
Maureen M L
MM
Chan
Kwok-Hung
KH
Leung
Wah-Shing
WS
Tang
Bone S F
BS
Chan
Veronica L
VL
Ng
Woon-Leung
WL
Sim
Tiong-Chee
TC
Ng
Ping-Wing
PW
Law
Kin-Ip
KI
Tse
Doris M W
DM
Peiris
Joseph S M
JS
Yuen
Kwok-Yung
KY
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009305:Nasopharynx / Q000821:virology; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012367:RNA, Viral / Q000032:analysis; D045473:Severe acute respiratory syndrome-related coronavirus / Q000302:isolation & purification*; D045169:Severe Acute Respiratory Syndrome / Q000097:blood / Q000401:mortality* / Q000821:virology*; D016019:Survival Analysis; D019562:Viral Load
D012367:RNA, Viral