A European multicentre evaluation of detection and typing methods for human enteroviruses and parechoviruses using RNA transcripts.

Polymerase chain reaction (PCR) detection has become the gold standard for diagnosis and typing of enterovirus (EV) and human parechovirus (HPeV) infections. Its effectiveness depends critically on using the appropriate sample types and high assay sensitivity as viral loads in cerebrospinal fluid samples from meningitis and sepsis clinical presentation can be extremely low. This study evaluated the sensitivity and specificity of currently used commercial and in-house diagnostic and typing assays. Accurately quantified RNA transcript controls were distributed to 27 diagnostic and 12 reference laboratories in 17 European countries for blinded testing. Transcripts represented the four human EV species (EV-A71, echovirus 30, coxsackie A virus 21, and EV-D68), HPeV3, and specificity controls. Reported results from 48 in-house and 15 commercial assays showed 98% detection frequencies of high copy (1000 RNA copies/5 µL) transcripts. In-house assays showed significantly greater detection frequencies of the low copy (10 copies/5 µL) EV and HPeV transcripts (81% and 86%, respectively) compared with commercial assays (56%, 50%; P = 7 × 10-5 ). EV-specific PCRs showed low cross-reactivity with human rhinovirus C (3 of 42 tests) and infrequent positivity in the negative control (2 of 63 tests). Most or all high copy EV and HPeV controls were successfully typed (88%, 100%) by reference laboratories, but showed reduced effectiveness for low copy controls (41%, 67%). Stabilized RNA transcripts provide an effective, logistically simple and inexpensive reagent for evaluation of diagnostic assay performance. The study provides reassurance of the performance of the many in-house assay formats used across Europe. However, it identified often substantially reduced sensitivities of commercial assays often used as point-of-care tests.

Risk of environmental transmission of norovirus infection from prior room occupants.

BACKGROUND: Environmental contamination of norovirus (NoV) is believed to be a significant source for further transmission in hospitals. AIM: To investigate the risk of acquiring NoV in a cleaned room previously occupied by a patient with NoV infection. The risk of having a roommate with recent NoV infection was also assessed. METHODS: In a retrospective cohort, comprising 33,788 room stays at five infectious Disease wards in southern Sweden from 2013 to 2018, the risk of acquiring NoV infection after admission to an exposed or non-exposed room was analysed with uni- and multivariable statistical analysis, controlling for age, colonization pressure and any roommate. RNA sequencing of the NoV strains involved in suspected room transmission was also performed. RESULTS: Five of the 1106 patients exposed to a room with a prior occupant with NoV infection and 49 in the non-exposed group acquired NoV infection. An association between NoV acquisition was found in the univariable analysis (odds ratio (OR) 3.3, P=0.01), but not when adjusting for potential confounders (OR 1.9, P=0.2). Sequencing of the NoV samples showed that only two of the five exposed patients with acquired NoV infection were infected by identical strains to the prior room occupant, inferring a room transmission risk of 0.2% (95% confidence interval 0.05-0.78%). None of the 52 patients who shared room with a roommate with NoV symptoms resolved for ≥48 h acquired NoV infection. CONCLUSIONS: In absolute terms, the risk of room transmission of NoV is low. Discontinuation of isolation ≥48 h after resolution of symptoms seems adequate.

Risk factors for hospital norovirus outbreaks: impact of vomiting, genotype, and multi-occupancy rooms.

BACKGROUND: Norovirus is frequently introduced to the hospital and is a frequent cause of hospital outbreaks. Recognition of the factors that facilitate or impede norovirus transmission is an important step to effectively prevent hospital outbreaks. AIM: To investigate risk factors for norovirus outbreaks in hospital settings. METHODS: Clinical data, ward setting, and norovirus genotype were collected from all 65 norovirus-positive index cases in outbreaks and all 186 sporadic norovirus cases at 192 wards in southern Sweden during 2010-2012 in a nested case-control study. Uni- and multivariate statistical analyses were conducted. FINDINGS: Outbreak was independently associated with the number of patients sharing a room with the norovirus case (odds ratio (OR): 1.9 per additional patient in the room; P < 0.01), vomiting (OR: 2.6; P = 0.04), age >80 years (OR: 3.2; P < 0.01), comorbidity (OR: 2.3; P = 0.05), and onset of symptoms after admission to the ward (OR: 3.5; P < 0.01) in the multivariate analysis. Infection with genotype GII.4 was found to be strongly associated with outbreak in the univariate analysis (OR: 5.7; P < 0.01). Moreover, associations between GII.4 and vomiting (OR: 2.5; P = 0.01) and old age (OR: 4.3: P < 0.01) were found. CONCLUSION: This is the first study to investigate clinical, ward and genotype risk factors for norovirus hospital outbreaks. Recognition of these factors may help direct and prioritize infection control actions based on the outbreak risk. The results also suggest that the outbreak association with GII.4 partly may be explained by an enhanced ability to induce vomiting.