Preben Aavitsland

Risk of Fetal Death after Pandemic Influenza Virus Infection or Vaccination

BACKGROUND During the 2009 influenza A (H1N1) pandemic, pregnant women were at risk for severe influenza illness. This concern was complicated by questions about vaccine safety in pregnant women that were raised by anecdotal reports of fetal deaths after vaccination. METHODS We explored the safety of influenza vaccination of pregnant women by linking Norwegian national registries and medical consultation data to determine influenza diagnosis, vaccination status, birth outcomes, and background information for pregnant women before, during, and after the pandemic. We used Cox regression models to estimate hazard ratios for fetal death, with the gestational day as the time metric and vaccination and pandemic exposure as time-dependent exposure variables. RESULTS There were 117,347 eligible pregnancies in Norway from 2009 through 2010. Fetal mortality was 4.9 deaths per 1000 births. During the pandemic, 54% of pregnant women in their second or third trimester were vaccinated. Vaccination during pregnancy substantially reduced the risk of an influenza diagnosis (adjusted hazard ratio, 0.30; 95% confidence interval [CI], 0.25 to 0.34). Among pregnant women with a clinical diagnosis of influenza, the risk of fetal death was increased (adjusted hazard ratio, 1.91; 95% CI, 1.07 to 3.41). The risk of fetal death was reduced with vaccination during pregnancy, although this reduction was not significant (adjusted hazard ratio, 0.88; 95% CI, 0.66 to 1.17). CONCLUSIONS Pandemic influenza virus infection in pregnancy was associated with an increased risk of fetal death. Vaccination during pregnancy reduced the risk of an influenza diagnosis. Vaccination itself was not associated with increased fetal mortality and may have reduced the risk of influenza-related fetal death during the pandemic. (Funded by the Norwegian Institute of Public Health.).

Outbreak of haemolytic uraemic syndrome in Norway caused by stx2-positive Escherichia coli O103:H25 traced to cured mutton sausages.

BackgroundOn 20–21 February 2006, six cases of diarrhoea-associated haemolytic uraemic syndrome (HUS) were reported by paediatricians to the Norwegian Institute of Public Health. We initiated an investigation to identify the etiologic agent and determine the source of the outbreak in order to implement control measures.MethodsA case was defined as a child with diarrhoea-associated HUS or any person with an infection with the outbreak strain of E. coli O103 (defined by the multi-locus variable number tandem repeats analysis (MLVA) profile) both with illness onset after January 1st 2006 in Norway. After initial hypotheses-generating interviews, we performed a case-control study with the first fifteen cases and three controls for each case matched by age, sex and municipality. Suspected food items were sampled, and any E. coli O103 strains were typed by MLVA.ResultsBetween 20 February and 6 April 2006, 17 cases were identified, of which 10 children developed HUS, including one fatal case. After pilot interviews, a matched case-control study was performed indicating an association between a traditional cured sausage (odds ratio 19.4 (95% CI: 2.4–156)) and STEC infection. E. coli O103:H25 identical to the outbreak strain defined by MLVA profile was found in the product and traced back to contaminated mutton.ConclusionWe report an outbreak caused by a rare STEC variant (O103:H25, stx2-positive). More than half of the diagnosed patients developed HUS, indicating that the causative organism is particularly virulent. Small ruminants continue to be important reservoirs for human-pathogen STEC. Improved slaughtering hygiene and good manufacturing practices for cured sausage products are needed to minimise the possibility of STEC surviving through the entire sausage production process.

Outbreak of Salmonella Thompson Infections Linked to Imported Rucola Lettuce

On November 15, 2004, a cluster of three cases of Salmonella Thompson infection was registered by the Norwegian reference laboratory. In the following days further cases occurred, prompting a case-control study among the first 13 cases and 26 matched controls. By December 31, 21 cases had been reported, with the first onset on October 24. Consumption of rucola lettuce (Eruca sativa, also known as rocket salad or arugula) (OR 8,8 [1,2-infinity]) and mixed salad (OR 5,0 [1,0-infinity]) was associated with illness. On November 26, Swedish authorities notified the finding of Salmonella Thompson in rucola lettuce through the EU Rapid Alert System for Food and Feed. Later, several countries reported finding this and other Salmonella serovars and Campylobacter in rucola produced in Italy. In response to our alert through the international Enter-net surveillance network, Sweden and England also reported an increase of cases. Salmonella Thompson isolates from products and patients from several countries showed high similarity by pulsed-field gel electrophoresis, but some isolates showed significant differences. We think that the outbreak in Norway reflected a larger international outbreak caused by rucola imported from one Italian producer. Findings of other pathogens indicate a massive contamination, possibly caused by irrigation with nonpotable water. Rapid international information exchange is invaluable when investigating outbreaks caused by internationally marketed products.

A large community outbreak of waterborne giardiasis-delayed detection in a non-endemic urban area.

BackgroundGiardia is not endemic in Norway, and more than 90% of reported cases acquire the infection abroad. In late October 2004, an increase in laboratory confirmed cases of giardiasis was reported in the city of Bergen. An investigation was started to determine the source and extent of the outbreak in order to implement control measures.MethodsCases were identified through the laboratory conducting giardia diagnostics in the area. All laboratory-confirmed cases were mapped based on address of residence, and attack rates and relative risks were calculated for each water supply zone. A case control study was conducted among people living in the central area of Bergen using age- and sex matched controls randomly selected from the population register.ResultsThe outbreak investigation showed that the outbreak started in late August and peaked in early October. A total of 1300 laboratory-confirmed cases were reported. Data from the Norwegian Prescription Database gave an estimate of 2500 cases treated for giardiasis probably linked to the outbreak. There was a predominance of women aged 20–29 years, with few children or elderly. The risk of infection for persons receiving water from the water supply serving Bergen city centre was significantly higher than for those receiving water from other supplies. Leaking sewage pipes combined with insufficient water treatment was the likely cause of the outbreak.ConclusionLate detection contributed to the large public health impact of this outbreak. Passive surveillance of laboratory-confirmed cases is not sufficient for timely detection of outbreaks with non-endemic infections.

Incidence of gastroenteritis in Norway - a population-based survey

In 1999-2000 we conducted a one-year, retrospective population-based survey in Norway to estimate the incidence of gastroenteritis and study the association with selected exposures. A self-administered questionnaire was mailed to 3000 persons selected at random from the population registry, with 250 persons being contacted each month. The response rate was 61%. The incidence of acute gastroenteritis was 1.2 per person-year. The incidence was higher for women than for men. Of the total of 171 cases, 29 (17%) consulted a physician, 13 (8%) reported that a stool sample was taken, and 7 (4%) were admitted to hospital. Among children aged less than 15 years, drinking water from a private water supply was associated with illness, while using chlorinated water was protective. Among adults aged 20-40 years, travelling abroad was associated with illness. The incidence in our survey is similar to rates found by FoodNet in United States.

Perspective: A Five-Country Analysis of the Impact of Four Different Haemophilus influenzae Type b Conjugates and Vaccination Strategies in Scandinavia

Prior to vaccinations against invasive Haemophilus influenzae type b (Hib) diseases in Scandinavia, first initiated in Finland in 1986, the incidence of cases in those five countries was 49/100,000/year in 0- to 4-year-olds and 3.5/100,000 overall. During the following decade, Hib conjugates administered to young children had approximately 95% effectiveness, regardless of which conjugate was used, whether two or three primary doses were administered, and at what age in early infancy the first vaccination was given. The herd immunity effect has extended protection to older age groups. A similar effectiveness of different conjugates in five countries despite considerable diversity in approach suggests that the same impact would occur in other regions with comparable epidemiology. The Scandinavian experience supports the view that three primary vaccine doses are not imperative, thus suggesting that reducing doses of costly Hib vaccines would be one way to facilitate their usage in regions with limited resources.

Severe consequences of healthcare-associated infections among residents of nursing homes: a cohort study.

The aim of this study was to identify the consequences of healthcare-associated infections in Norwegian nursing homes, to include debilitation, hospital transfer and mortality. We followed the residents of six nursing homes in two major cities in Norway during the period October 2004 to March 2005. For each resident with infection we randomly selected two controls among residents who did not have an infection. Cases and the controls were followed for 30 days as a cohort in order to measure the incidence of complications and risk ratio (RR) in the two groups. The incidence of infection was 5.2 per 1000 resident-days. After 30 days follow-up 10.9% of residents who had acquired infection demonstrated a reduction in overall physical condition compared with 4.8% in the unexposed group (RR: 2.3). Altogether 13.0% of residents with infections were admitted to hospital compared with 1.4% in the unexposed group (RR 9.2), and 16.1% residents with infections died in the nursing home during follow-up compared with 2.4% in the unexposed group (RR: 6.6). Residents with lower respiratory tract infections demonstrated higher morbidity and mortality. In conclusion, healthcare-associated infections cause severe consequences for people living in nursing homes, including debilitation, hospital admission and death.

An Outbreak of Pseudomonas aeruginosa Infection Caused by Contaminated Mouth Swabs

BACKGROUND Pseudomonas aeruginosa is an opportunistic bacterium that can cause severe infection in susceptible patients. During the winter of 2001-2002, we investigated an outbreak of P. aeruginosa infection among patients in several hospitals across Norway. METHODS A nationwide outbreak investigation was performed with case finding, questionnaires, and product sampling. All available clinical and environmental P. aeruginosa strains were genotyped. Detailed information was collected from patients with the outbreak strain or with any P. aeruginosa in blood or cerebrospinal fluid samples. To identify risk factors, we conducted a case-control study among patients with P. aeruginosa isolated from blood or cerebrospinal fluid samples during October 2001-December 2002. Case patients were patients infected with the outbreak genotype, and control subjects were patients infected with other genotypes. RESULTS A total of 231 patients from 24 hospitals were identified as having the outbreak strain; 39 of these patients had positive blood culture results. Seventy-one patients (31%) died while hospitalized; all of the patients who died had severe underlying disease. Among 39 case patients and 159 control subjects, use of the moist mouth swab (adjusted odds ratio, 5.3; 95% confidence interval, 2.0-13.6) and receipt of mechanical ventilation (adjusted odds ratio, 6.4; 95% confidence interval, 2.3-17.2) were associated with infection due to the outbreak strain. Genotypically identical strains of P. aeruginosa were identified in 76 mouth swabs from 12 different batches and from the production line. CONCLUSIONS Contamination of mouth swabs during production caused the largest-ever outbreak of P. aeruginosa infection in Norway. Susceptible patient groups should use only documented quality-controlled, high-level-disinfected products and items in the oropharynx.

Hospital-Acquired Infections in Norway: A National Prevalence Survey in 1991

A 1-day prevalence survey of hospital-acquired infections (HAI) was carried out in Norwegian somatic hospitals in 1991. The survey aimed at assessing the problem of HAI. 950 infections were found among the 14977 surveyed patients (prevalence rate 6.3%). HAI were more prevalent in combined intensive care units (prevalence rate 22%), surgical intensive care units (17%), haematological wards (15%), special care baby units (14%), and geriatric wards (14%). Urinary tract infections were most prevalent (33% of all HAI) followed by respiratory tract infections (21%) and surgical wound infections (17%). 157 (3.6%) of the 4382 patients who had undergone surgery, had a surgical wound infection. With a high response rate (76 out of 84 hospitals) and a sensitive method of screening the patients (chart review and bedside examination), this survey gives a fairly reliable measure of the prevalence of HAI in Norwegian somatic hospitals.

Shigella dysenteriae serotype 1 in west Africa: intervention strategy for an outbreak in Sierra Leone

In November 1999, a Médecins Sans Frontières team based in the southeastern part of Sierra Leone reported an increased number of cases of bloody diarrhoea. Shigella dysenteriae serotype 1 (Sd1) was isolated in the early cases. A total of 4218 cases of dysentery were reported in Kenema district from December, 1999, to March, 2000. The overall attack rate was 7.5%. The attack rate was higher among children younger than 5 years than in the rest of the population (11.2% vs 6.8%; relative risk=1.6; 95% CI 1.5-1.8). The case fatality was 3.1%, also higher for children younger than 5 years (6.1% vs 2.1%; relative risk=2.9; 95% CI 2.1-4.1]). Among 583 patients regarded at increased risk of death who were treated with ciprofloxacin in isolation centres, case fatality was 0.9%. A 5-day ciprofloxacin regimen, targeted to the most severe cases of bloody diarrhoea, was highly effective. This is the first time a large outbreak caused by Sd1 has been reported in west Africa.