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.

Epidemiology of MRSA in southern Sweden: strong relation to foreign country of origin, health care abroad and foreign travel.

All notified MRSA cases in Skåne County have been followed since 2000. We have investigated the MRSA epidemiology over time, method of acquisition, whether some spa types are more prone to spread, and/or cause more infections, and the connection between spa type and country of acquisition/origin. All cases between 2000 and 2010 were included. Infection or colonization and the presence of PVL genes were noted. The spa types of the index cases were correlated with community or healthcare acquisition, proportion of MRSA-positive household contacts, country of origin of families and country of acquisition of MRSA. The number of cases increased from 31 in 2000 to 315 in 2010. Most cases were community-acquired and the median age was 30 years. Thirty-two per cent of the MRSA cases were found because of a clinical infection. Of the household contacts 35 % were MRSA-positive. Only 24 % of the MRSA cases were both of Swedish origin and had contracted MRSA in Sweden. An association between spa type and certain regions of acquisition/origin was noted. Spa types t044, t002 and t008 were the most predominant strains. PVL-positive spa types t008, t019 and t044 caused more skin infections than the other spa types. Our results support screening for MRSA in patients with health care contacts abroad, culturing of patients with skin infections contracted outside Sweden and performing contact tracing among household members. Knowledge of spa type might give guidance in the process of contact tracing. Eradication treatment of MRSA spa types causing more skin infections may be warranted.

MRSA in children from foreign countries adopted to Swedish families.

AIM: To determine if children adopted to Swedish families from countries with a high carrier rate of methicillin-resistant Staphylococcus aureus (MRSA) are infected or colonized with MRSA. METHODS: From January 2000 to May 2005, 23 adopted children from 6 countries were examined for MRSA at the University hospital in Lund after their arrival in Sweden. RESULTS: Thirteen of the 23 children (57%) were MRSA positive with a median age of the children at the time MRSA was detected of 6 (range 3-16) months. All MRSA positive children had a history of hospitalization in their native country before arriving in Sweden. The throat was the most frequent and persistent site where MRSA was seen while in sites such as the anterior nares and perineum, MRSA was found more intermittently. The MRSA-positive children were adopted into 13 Swedish families and in 3 families, 6 of 10 family members became MRSA positive. CONCLUSION: Children adopted from foreign countries to Swedish families and with a history of hospitalization in their native country were commonly colonized with MRSA. The throat was the most frequent site colonized and transmission of MRSA from adopted children to other family members occurred.