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Guideline for the Prevention and Control of Norovirus Gastroenteritis Outbreaks in Healthcare Settings, 2011

Evidence Table Q1 - Person characteristics / Clinical Characteristics

Author, Yr (Ref) Study Design Quality Study Objective Population and Setting N Results Comments Ref ID_Data extracted by
Mattner, F; 2005 56 Systematic review 1, 2, 3 To investigate the effect of the index case (i.e., patient vs. staff) on infection risk and outbreak size. All published nosocomial norovirus outbreaks with proven or suspected person-to-person transmission. Inclusion for statistical analyses limited to outbreaks with epidemic curves for each ward and outbreaks where the index case could be identified. 1033 individuals among 30 outbreaks included in the study. Index case in outbreaks
Patient vs. staff – 20/30 (67%) vs. 10/30 (33%) Symptomatic norovirus infection
All results index case: patient vs.staff (95% CI for difference in mean); p value (30 wards included)
Mean number of affected patients – 27.75 vs 11.5 (5.1-27.0); 0.006
Mean number of affected staff – 11.75 vs 12.8 (-9.0 -6.9); 0.78
Mean number of overall affected individuals – 39.5 vs 24.3 (1.1-29.0); 0.36 All results index case: patient vs. staff; OR (95% CI); p value (7 wards included)
Number of affected patients - 154/356 vs. 21/153; 4.79 (1.82-8.28); <0.0005
Number of affected staff – 79/224 vs. 36/136; 1.51 (0.92-2.49); 0.08
Sources include Medline search from 1962-2004 using search terms: “norovirus”, “Norwalk virus”, “small round structured virus”, and “outbreak”; Outbreak Worldwide Database; German data in Epidemiologisches Bulletin; data from personal communication with a German teaching hospital; and author’s own data. Power and sample size not reported. 520_IL
Mattner, F; 2006 57 Prospective controlled study 1,3,4,6,7 To characterize risk factors for the clinical complications of norovirus infections (e.g. vomiting, diarrhea, potassium decrease, creatinine increase, C-reactive protein increase) All individuals working in or admitted to five wards (psychiatry, nephrology, gastroenterology, cardiology and trauma) at a university hospital in Germany in the period from the onset of clinical symptoms of the first patient until 2 days after the last patient became symptom free.
All patients and staff members who were affected with a sudden onset of diarrhea and/or vomiting were included as cases. Patients admitted with clinical signs were regarded as index cases, and patients admitted ≥48 hrs before developing clinical signs were regarded as nosocomial cases 84 patients (72 acquired infection nosocomially) and 79 staff members (60 nurses). 3 norovirus positive patients were excluded from risk factor analysis. N for risk factor analyses was 53 for all outcomes except C reactive protein increase (N=52)
Clinical features in patients (study duration 3 months)
Diarrhea – 79/84; 95%
Vomiting – 57/84; 68%
Somnolence – 2/84; 2%
Serum creatinine increase > 10% – 22/84; 26%
Serum potassium decrease > 20% – 7/84; 8% Comparisons of attack rates in patients and nurses (study duration 3 months)
All results are attack rate (%) in patients vs. nurses; P value
Psychaitry ward – 78 vs. 88; <0.01
Nephrology ward – 32% in the first period and 33% in the second period in patients. Data for nurses not given
Gastroenterology – 27 vs. 90; <0.01
Cardiology – 42 vs. 44; 0.87
Trauma – 35 vs. 83; <0.01
Total – 38 vs. 76; <0.01 Risk factors for complications of norovirus (study duration 3 months) Vomiting>1 day:
Univariate analysis: All results OR; P value
Age > 65 years – 1.84; 0.30
Male gender – 0.91; 1.00
Underlying cardiovascular disorders – 2.7; 0.13
Underlying gastrointestinal disorders – 0.34; 0.31
Underlying autoimmune disease – 0.81; 1.00
Underlying renal disorders – 0.95; 1.00
Renal transplant – 1.31; 0.75
Underlying malignancy – P value 0.18; OR not reported
Underlying trauma – 1.14; 1.00
Immunosuppressive therapy – 0.92; 1.00
Community acquired norovirus – 2.36; 0.19 Multivariate analysis: All results OR (95% CI)
Underlying cardiovascular disorders – 7.17(1.59-51.2)
Community acquired norovirus – 5.54(1.04-42.8) Diarrhea>2 days:
Univariate analysis: All results OR; P value
Age > 65 years – 3.58; 0.01
Male gender – 2.15; 0.12
Underlying cardiovascular disorders – 2.80; 0.15
Underlying gastrointestinal disorders – 0.22; 0.03
Underlying autoimmune disease –  4.67; 0.24
Underlying renal disorders – 1.77; 0.39
Renal transplant – 1.71; 0.54
Underlying malignancy – 0.07; 0.01
Underlying trauma – 0.27; 0.053
Immunosuppressive therapy – 1.29; 0.79
Community acquired norovirus – 3.09; 0.06 Multivariate analysis: All results OR (95% CI)
Age > 65 years – 11.56(1.89-224.00)
Underlying malignancy – 0.02(0.00-0.19)
Underlying trauma – 0.05(0.00-0.55) Potassium decrease >20%:
Univariate analysis: All results OR; P value
Age > 65 years – 0.94; 1.00
Male gender – 0.90; 1.00
Underlying cardiovascular disorders – 5.17; 0.06
Underlying gastrointestinal disorders – 0.46; 0.67
Underlying autoimmune disease – 0.98; 1.00
Underlying renal disorders – 1.74; 0.71
Renal transplant – 3.91; 0.09
Underlying malignancy – P value 0.58; OR not reported
Underlying trauma – P value 0.19; OR not reported
Immunosuppressive therapy – 2.83; 0.25
Community acquired norovirus – 0.48; 0.68 Multivariate analysis: All results OR (95% CI)
Underlying cardiovascular disorders – 17.10(2.17-403.00)
Renal transplant – 13.02(1.63-281.00) Creatinine increase >10%:
Univariate analysis: All results OR; P value
Age > 65 years – 1.04; 1.00
Male gender – 1.79; 0.24
Underlying cardiovascular disorders – 0.60; 0.42
Underlying gastrointestinal disorders – 1.93; 0.36
Underlying autoimmune disease – 4.50; 0.12
Underlying renal disorders – 1.44; 0.59
Renal transplant – 3.53; 0.07
Underlying malignancy – 0.93; 1.00
Underlying trauma – 0.07; <0.01
Immunosuppressive therapy – 5.74; <0.01
Community acquired norovirus – 5.07; 0.01 Multivariate analysis: All results OR (95% CI)
Immunosuppressive therapy – 5.67(1.78-20.1) C Reactive Protein >58 mg:
Univariate analysis: All results OR; P value
Age > 65 years – 0.81; 0.79
Male gender – 2.63; 0.11
Underlying cardiovascular disorders – 0.32; 0.06
Underlying gastrointestinal disorders – 1.54; 0.55
Underlying autoimmune disease – 3.71; 0.14
Underlying renal disorders – 2.13; 0.19
Renal transplant – 1.33; 0.76
Underlying malignancy – 2.96; 0.25
Underlying trauma – 0.23; 0.35
Immunosuppressive therapy – 3.38; 0.06
Community acquired norovirus – 2.30; 0.23 Multivariate analysis: All results OR (95% CI)
Underlying malignancy – 9.07(1.17-193.00)
Immunosuppressive therapy – 5.37(1.62-19.9)
Diarrhea was defined as three or more episodes of loose stools in a 24 hr period. Cases were considered to be norovirus-positive if samples from at least two patients from the same ward were positive by norovirus-specific RT-PCR. Power and sample size not reported 358_RA
Lopman, BA; 2004 58 Prospective controlled study 1,2,3,4 To describe norovirus outbreaks in residential homes or hospitals of principally older individuals. Patients in hospitals and nursing homes in England. Cases were hospital patients, nursing home residents, and health care staff with ≥2 episodes of vomiting, ≥3 episodes of diarrhea, or both during a 24-hour period. Those with symptoms due to incontinence or ingestion of laxative drugs were excluded. 271 outbreaks – 33 in nursing homes and 238 in hospital units.
4378 cases – 2154 hospitalized patients, 1360 hospital care staff, 505 nursing home residents, and 358 nursing home staff.
Duration of illness
Hospital patients vs. hospital staff, nursing home staff, and nursing home residents (75th percentile); p value – 3 days (5 days) vs. 2 days (3 days); p<0.001 Recovery was slowest in the oldest age group (≥85 years) of hospitalized patients - 40% symptomatic after 4 days  
Outbreak is defined as ≥ 2 cases in a hospital functional care unit with dates of onset within 7 days of each other. Power and sample size not reported. Promotion of active surveillance (2-tiers of clinical symptoms) to detect cases as a means of prevention of outbreaks 642_IL
Rodriguez-Guillen, L; 2004 60 Prospective controlled study 2,4 To investigate the frequency of human CaCV (norovirus and sapovirus) in stool samples from adults and children with HIV. Adults and children with and without HIV from Venezuela. Stool samples – 240 from adults and 81 from children.
Subjects – 209 adults and 65 children. 
Detection in children vs adults; p value
CaCV – 62/159 vs 10/81; <0.0001
Novorivus GI – 4% detected exclusively from adults
norovirus GII – 20% vs 4%; <0.01 Detection in HIV positive vs negative subjects; p value
Adults – 22/108 vs 6/51; NS
Children – 22/43 vs 9/38; 0.0111 Detection in subjects with vs without diarrhea
HIV positive adults – 3/32 vs 10/76; 0.4234
HIV negative adults – 3/26 vs 3/25; 0.6468
HIV positive children – 11/18 vs 11/25; 0.2681
HIV negative children – 5/17 vs 4/21; 0.3565
Diarrhea defined as the occurrence of three or more bowel movements within a 24 hour period with decrease in stool consistency. Outcomes determined using RT-PCR. Power and sample size not reported. 502_IL      
Thea, D; 1993 65 Prospective controlled study 1,3,4 To determine the prevalence of enteric viruses and their relation to diarrhea, wasting and immunosuppression among HIV infected and uninfected persons. Adult general medical patients admitted to a hospital in Zaire. 57% were HIV positive. 10/198 patients had SRSV infection. 234 enrolled, 198 analyzed Presence of diarrhea in patients shedding norovirus
Of 10 patients shedding norovirus, 2 had acute diarrhea, 2 had chronic diarrhea and 6 had no diarrhea Presence of HIV infection in patients shedding norovirus
Of 10 patients shedding norovirus, 5 had HIV infection (1 Stage III and 4 Stage IV) and 5 did not. Asymptomatic norovirus infection -  Viral shedding
Association with HIV infection
HIV positive vs. HIV negative – 17% vs. 18%; P=0.82
Viral shedding vs. no viral shedding (Stage III HIV positive) – P=0.80
Viral shedding vs. no viral shedding (Stage IV HIV positive/AIDS) – P=0.79 Association with degree of immunocompromise (defined by CD4/CD8 ratio)
All results P values for test of trend towards greater frequency of shedding among lower CD4/CD8 quintiles
Overall – P=0.14
Among HIV positive – 0.07
Among HIV negative – 0.45
norovirus was detected by EM. HIV Stages:
I: Asymptomatic
II: Mild disease
III: Moderate disease
IV: Acquired immune deficiency syndrome (AIDS) Power and sample size not reported
1606_RA
Lee, N; 2007 59 Retrospective controlled study 1,2,3,4,6,7 To study the association between fecal viral concentration and clinical manifestations of GII.4 norovirus infection. Risk factors for prolonged diarrhea were also studied. Patients ≥16 yrs of age at 2 regional hospitals in Hong Kong. Mean age 60 years; 37.5% male. 44 enrolled; 40 analyzed Factors associated with higher  median fecal viral concentration (during a 2 year study period)
Univariate analysis (All results P value)
Age ≥ 65 yrs – 0.06
Female gender – 0.71
Pre-existing medical conditions – 0.52
Prolonged duration of diarrhea – <0.01
Frequency of vomiting – 0.22
Frequency of fever – 0.38 Correlation analysis (All results Spearman correlation coefficient, P value)
Total duration of diarrhea – 0.47; <0.01
Total frequency of vomiting – 0.34; 0.04 Risk factors for prolonged duration of diarrhea (during a 2 year study period)
Univariate analysis (All results P value)
Age ≥ 65 yrs – <0.05
Pre-existing medical conditions – <0.05
Frequency of fever – 0.01 Multivariate analysis (All results OR; 95% CI)
Fecal viral concentration (per log10 copies) – 9.56(1.18-77.57)
Age (per year) – 1.15(1.03-1.28)
Cases were included for analysis if stool samples were collected ≤ 96 hours from symptom onset. Diarrhea was defined as having ≥ 3 loose stools per day. Diagnosis of norovirus infection and its quantitation were based on RT-PCR assay of stool samples. Prolonged diarrhea was defined as ≥ 4 days of diarrhea Power and sample size not reported Correlation between norovirus concentration and duration of illness (not severity) 2416_RA
Marx, A; 1999 66 Retrospective controlled study 1,3,4 To assess risk factors for gastroenteritis associated with Norwalk-like viruses (NLVs) Residents and employees at a geriatric long term care facility. 68% residents were female, median age was 83 yrs (range 65-106). 78% of employees were female, median age was 36 yrs. Study was conducted in Washington State. 91 residents and 97 employees All results RR(95% CI); P value for the presence of risk factor
Risk factors for symptomatic norovirus infection among residents
Physical dependence – 3.5(1.0-12.9);0.02
Respiratory therapy – 2.3(0.8-6.4); 0.20
Antibiotics – 1.6(1.0-2.8); 0.20
Chronic infections – 1.6(0.9-3.0); 0.40
Tube feeding – 1.3(0.7-2.6); 0.70
Disoriented – 1.2(0.8-1.8); 0.60
Diuretics – 0.4(0.2-0.9); 0.02 Risk factors for symptomatic norovirus infection among employees
Exposure to vomitus – 2.6(1.1-6.5); 0.03
Gastroenteritis in household – 2.3(1.4-3.6); 0.01
Exposure to residents with gastroenteritis – 2.2(1.0-4.9); 0.05
Resident care – 1.4(0.8-2.5); 0.30
Tap water – 0.9(0.5-1.5); 0.60
Ice – 0.7(0.4-1.2); 0.20 Symptomatic norovirus infection (Effect of protective measures among nursing staff)
Gowning – 0.4(0.1-1.4)
Strict hand washing – 0.7(0.2-1.3)
Use of hand-disinfection gel – 0.8(0.4-1.4)
Laundering work clothes daily – 1.2(0.7-1.3)  
A case of acute gastroenteritis was defined as an individual with onset of vomiting or diarrhea during the study period (Feb 12 – Mar 20 1996); diarrhea was defined as ≥2 loose or watery stools in a 24 hr period. A single NLV strain of genogroup II genetically related to Toronto virus was the only pathogen identified. NLVs were identified by EM in stool and vomitus specimens and further characterized by RT-PCR and nucleotide sequencing. Data on residents was collected through medical records. 90 of 97 employees completed a self-administered questionnaire Power and sample size not reported 1237_RA
Caceres, V; 1998 67 Retrospective controlled study 1,3,4  To identify the etiologic agent and risk factors associated with a hospital ward outbreak of gastroenteritis. Patients and staff on a medical-surgical ward in South Carolina where the index case (a nursing staff member) worked. Overall demographics not reported. 89 staff and 91 patients Symptomatic norovirus infection - Attack rate (during the study period)
Staff vs. patients – 28/89 vs. 10/91; RR(95% CI) = 2.9(1.5-5.5) Symptomatic norovirus infection among staff
All results RR(95% CI) (comparisons not clear, assume the opposite of the risk factor given)
Stayed in hospital overnight – 2.0(1.0-3.9)
Assisted ill patients – 1.1(0.6-2.2)
Worked longer hours – 1.8(1.0-3.5)
Used staff bathroom on ward – 22/61 vs. 0/1; RR undefined
Ate in cafetaria – 1.5(0.7-3.1)
Brought own food – 1.1(0.6-2.1)
Consumed water from ward – 1.4(0.7-2.8)
Consumed ice from ward – 1.1(0.2-5.5)
Changing bed sheets without golves – 1.7(0.7-4.0)
Changing urine catheters without gloves – 0/0 vs. 17/54; RR undefined
Turning patients without gloves – 0.8(0.4-1.9) Symptomatic norovirus infection among household members
Case staff vs. non-case staff – 5/27 vs. 7/69; 1.8(0.6-5.3) Symptomatic norovirus infection among patients
All results RR(95% CI) (comparisons not clear, assume the opposite of the risk factor given)
ED vs. admitted directly from home – 1.3(0.4-4.5)
Regular diet - 1.4(0.4-4.4)
Full ambulation – 2.6(0.7-9.5)
Physical therapy – 0.8(0.2-2.9)
Urinary catheter care – 1.2(0.4-4.0)
Nasogastric tube care – 0/5 vs. 10/86; RR undefined
Wound care – 0/24 vs. 10/67; RR undefined
Respiratory care – 5.7(1.8-18.1) Risk  of symptomatic norovirus infection associated with patient  nurse exposures
All results RR(95% CI)
Patients – on a shift with an assigned primary nurse who had onset of illness in the preceding 48h vs. not – 14% vs. 0%; RR undefined
Nurses – on a shift with an assigned primary patient who had onset of illness in the preceding 48h vs. not – 0.3(0.1-1.1) Discharge diagnoses of vomiting, diarrhea or viral gastroenteritis
Month of outbreak vs. same month previous year – 79/3567 vs. 63/3982; P<0.05 Etiologic agent
EM identified SRSV in 9 of 9 stool samples
A case was defined as a staff member or patient who had acute onset of vomiting and diarrhea from January 5-13, 1996 as recorded in patient charts. A patient was considered to be exposed if he or she had been taken care of by a case-nurse (an assigned nurse who was a primary caretaker) who had developed the illness in the preceding 48 hours. Staff exposure was ascertained if care of a symptomatic patient occurred within 48 hours All stool and vomit specimens were obtained within 48 hours after the onset of gastroenteritis. Specimens were examined by EM for viral particles and by RT-PCR for SRSV RNA Power and sample size not reported 1324_RA
Cegielski, J; 1994 68 Controlled study based on a cross-sectional survey None To determine whether specific viruses were associated with HIV infection HIV infected and HIV uninfected Tanzanian children admitted with chronic diarrhea, and controls without diarrhea aged 15 months to 5 years.  Consecutive sample (n=59)Not reported Asymptomatic norovirus infection
HIV infected children with chronic diarrhea vs. HIV uninfected children with chronic diarrhea – 4/21 vs. 1/32; Prevalence Ratio (90% CI) – 6.09(1.03-36.14) Rotavirus and coronavirus particles were not associated with HIV infection.
Enteric viruses were identified by EM of fecal specimens. Asymptomatic infection defined as presence of SRSV Power and sample size not reported 1525_RA

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