Characterization of human invasive isolates of Listeria monocytogenes in Sweden 1986-2007.

Since 1986, 68% of the Listeria monocytogenes isolates from human cases of invasive listeriosis in Sweden are available for retrospective studies. The aim of the present study was to characterize 601 human invasive isolates of L. monocytogenes in Sweden from 1986 to 2007 by using serotyping and pulsed-field gel electrophoresis. Since 1996, serovar 4b was permanently reduced to the second or third most common serovar in human cases in Sweden. During the latter period, 2000-2007, only 13% belonged to serovar 4b and 71% to 1/2a. The dendrogram, based on pulsovars, reveals two clusters with different serovars. Cluster 1 exhibits serovars 4b and 1/2b, whereas cluster 2 consists of serovar 1/2a. Serovar 1/2a seems to be more heterogeneous than serovar 4b.

Red fox and tick-borne encephalitis (TBE) in humans: can predators influence public health?

Analysing datasets from hunting statistics and human cases of tick-borne encephalitis (TBE), we found a positive correlation between the number of human TBE cases and the number of red fox (Vulpes vulpes). Time lags were also present, indicating that high numbers of red fox in 1 y translated into high numbers of human TBE cases the following y. Results for smaller predators were mixed and inconsistent. Hares and grouse showed negative correlations with human TBE cases, suggesting that they might function as dilution hosts. Combining our findings with food web dynamics, we hypothesize a diversity of possible interactions between predators and human disease - some predators suppressing a given disease, others enhancing its spread, and still others having no effect at all. Larger-sized predators that suppress red fox numbers and activity (i.e. wolf, Canis lupus; European lynx, Lynx lynx) were once abundant in our study area but have been reduced or extirpated from most parts of it by humans. We ask what would happen to red foxes and TBE rates in humans if these larger predators were restored to their former abundances.

Children born to HIV-1-infected women in Sweden in 1982-2003: trends in epidemiology and vertical transmission.

To describe the HIV-1 epidemic among childbearing women and their children in Sweden, a population-based analysis of data on all known mother-child pairs in Sweden with perinatal exposure to HIV-1 1982-2003 was conducted. The mother-to-child transmission (MTCT) rate in children prospectively followed from birth decreased from 24.7% in 1985-1993 to 5.7% in 1994-1998 and 0.6% in 1999-2003. The use of antiretroviral treatment of the mother during pregnancy and/or prophylactic antiretroviral intervention increased from 2.3% to 91.6% during the same period, and the elective cesarean delivery rate increased from 8.0% to 80.3%. No MTCT of HIV-1 occurred in Sweden after 1999.Fifty-one vertically HIV-1-infected children aged 2.7 to 17.6 years were living in Sweden by 31 December 2003, 71% being treated with antiretroviral agents. No HIV-1-related child death has been reported in Sweden after 1996. The conclusion is that MTCT of HIV-1 can be almost eliminated when appropriate resources are available. A national pregnancy screening program for HIV-1 running since 1987 with a high acceptance rate and the implementation of measures to prevent MTCT since 1994 have resulted in a significant decrease in the number of infected children. Inasmuch as knowledge of the infection status of the mother is crucial for reduction in MTCT of HIV-1, continued antenatal screening is important even in a low-prevalence country such as Sweden.

Endemic tularemia, Sweden, 2003.

Tularemia cases have been reported in Sweden since 1931, but no cyclical patterns can be identified. In 2003, the largest outbreak of tularemia since 1967 occurred, involving 698 cases. Increased reports were received from tularemia-nonendemic areas. Causal factors for an outbreak year and associated geographic distribution are not yet understood.

[Nepropathia epidemica on the increase and spreading south in Sweden]. / Sorkfeber i Sverige okar och sprider sig söderut.

2.086 cases of laboratory-confirmed NE were reported in Sweden during the 7-year period 1997-2003. The average age of the patients was 49,3 years and 62 per cent were men. Most cases were reported during the winter. The yearly incidence rates ranged from 1.6 cases per 100.000 in 2000 to 6.3 cases per 100.000 in 1998 varying with a 3 year cyclicity. The majority of cases were reported from the northern most counties of Sweden. The highest incidence rate was found in the county of Västerbotten (70 cases per 100.000 in 1998). However the number of cases further south seem to increase. The total number of reported cases has also increased. Comparison with previous 7-year period (1990-1996) gives an increase of 86 per cent. Handling fire-wood and hay are risk activities as well as cleaning and dusting in summerhouses.

[HIV in Sweden--more and more part of the world epidemic]. / HIV i Sverige--alltmer en del av världsepidemin.

During the years 1997-2001 there were 1213 cases of HIV reported in Sweden. By using a questionnaire sent to respective clinics, additional information was obtained for 1018 patents. The transmission routes were: 28 per cent homosexual, 65 per cent heterosexual, 10 per cent intravenous drug abuse, 1 per cent blood transfusion (none in Sweden) and 6 per cent other/unknown. 61 per cent of men infected by sex with men had contracted their infection in Sweden whilst this was true for 14 per cent of heterosexually infected men and 20 per cent of heterosexually infected women. Instead many with heterosexually transmitted infections had been infected in Africa or Asia where in many cases the patients also originated from. In 15 per cent of cases the HIV infection was detected in conjunction with a diagnosis of aids. Partner notification led to at least 0.12 (127/1018) new cases per index case.

Timeliness of case reporting in the Swedish statutory surveillance of communicable diseases 1998--2002.

To prepare for a new communicable disease act in Sweden, we performed an in-depth analysis of the performance of the present notification system (1998--2002). Four diseases were selected for analysis (meningococcal infection, salmonellosis, infection with penicillin-resistant pneumococci and tularaemia). Each step in the double notification flow (clinical and laboratory notifications) was studied and paper-based and electronic notifications compared. More than 15 possible single dates in the notification flows were analysed for 27,000 cases. The shortest notification flows (from date of sample collection to when the first notification was received at SMI--clinical or laboratory notification) were seen for meningococcal infections and salmonellosis (median 7 d) and the longest for tularaemia (11 d). Laboratory notifications were faster than clinical notifications, and electronic reporting 1.5-1.7 times faster than paper notifications. Further gains should be expected from the new electronic reporting system (SmiNet2), which will allow also clinical reporting electronically over the internet.

The 2000 tularemia outbreak: a case-control study of risk factors in disease-endemic and emergent areas, Sweden.

A widespread outbreak of tularemia in Sweden in 2000 was investigated in a case-control study in which 270 reported cases of tularemia were compared with 438 controls. The outbreak affected parts of Sweden where tularemia had hitherto been rare, and these "emergent" areas were compared with the disease-endemic areas. Multivariate regression analysis showed mosquito bites to be the main risk factor, with an odds ratio (OR) of 8.8. Other risk factors were owning a cat (OR 2.5) and farm work (OR 3.2). Farming was a risk factor only in the disease-endemic area. Swollen lymph nodes and wound infections were more common in the emergent area, while pneumonia was more common in the disease-endemic area. Mosquito bites appear to be important in transmission of tularemia. The association between cat ownership and disease merits further investigation.

Is the increase in notifications of Chlamydia trachomatis infections in Sweden the result of changes in prevalence, sampling frequency or diagnostic methods?

Based on clinical and laboratory surveillance data, trends in the incidence rates of genital Chlamydia trachomatis infections in Sweden between 1991 and 1999 were analysed according to age group and sex. The influence of changes in laboratory methods on the reported infections was assessed. After a decrease in the incidence rate of infection of 36% between 1991 and 1994, followed by a period of stability, a 20% increase was observed between 1997 and 1999 (from 157 to 189/100,000). Between 1991 and 1999 the female:male ratio decreased from 1.7 to 1.4. Incidence rates started to increase in 1994 in the 15-19 y age group for both sexes. Crude Chlamydia positivity increased from 4.1% (352,050 people tested) in 1994 to 5.4% (305,946 people tested) in 1999. This increase in Chlamydia positivity was seen both in laboratories that had changed to more sensitive methods and in those that had not. Changes in laboratory methods can therefore only partially explain the increase in notified cases. Increased screening of men may have contributed to the increase, but rising incidence rates in all young age groups of both sexes suggest a true increase in prevalence.