First wave of SARS-COV2 in Europe: Study and typology of the 15 worst affected European countries.

Since 11 March 2020 when officially declared a global pandemic, Covid-19 (or SARS-COV2) has turned out to be a multifaceted disease differently affecting countries and individuals. What makes certain countries more vulnerable than others has attracted the interest of scientists from various disciplines. This paper intends to compare the impact of demographic parameters, population health conditions and policy actions on prevalence and fatality levels of Covid-19 during the first 3 months since its declaration of global pandemic. A country-level exploratory analysis has been conducted in order to assess how demography, national health conditions and measures taken interact and condition the disease outcomes. Analysis relies on publicly available data on Covid-19 reported cases, deaths and number of persons tested. Those data are combined with demographic parameters (sex ratio, mean age, population density and life expectancy), health data (cardiovascular death rate, diabetes prevalence, share of smokers among males and females and number of hospital beds) and information about relative national policies aiming the management of the pandemic (lockdown timing and duration). Our analysis confirms the diversity of factors and the complexity of their interaction in explaining the propagation and fatality of the disease across Europe. Our findings question some well-established attitudes concerning the role of demographic variables and public health conditions in the spread of the disease.

Modelling the impact of different testing strategies for HCV infection in Switzerland.

OBJECTIVE: Hepatitis C virus (HCV) infection is a major cause of liver disease. Since symptoms of chronic liver disease usually appear only late in the course of the disease, infected individuals may remain undiagnosed until advanced disease has developed. We aimed to investigate which screening strategies would be most effective to detect individuals unaware of their infection. METHODS: We developed a mathematical model for HCV disease progression and compared the current practice of HCV testing in Switzerland with the following screening strategies: intensive screening of active injection drug users (IDU), screening of former IDU, screening of individuals originating from countries with high HCV prevalence, screening of individuals born 1951-1985 (birth-cohort) and universal screening. All screening interventions were considered in addition to a baseline scenario that reflected the current practice of HCV testing. RESULTS: Within the first 4 years (2018-2021), every year, on average 650 cases were diagnosed in the baseline scenario, 660 with intensified IDU screening, 760 with former IDU screening, 830 with origin-based screening, 1420 with birth-cohort screening and 1940 with universal screening. No difference in liver-related mortality and incidence of end-stage liver disease between the screening scenarios was observed. CONCLUSION: Our results suggest that only large-scale screening of the general population could substantially accelerate the rate of HCV diagnosis and treatment in Switzerland and other countries with similar epidemics. However, this implies screening of a large population with low prevalence, and may trigger considerable numbers of false-positive and borderline test results.

Approaching measles elimination in Switzerland: changing epidemiology 2007-2018.

Switzerland is aiming to eliminate measles, in line with the objectives of the World Health Organization (WHO). Physicians, laboratories and public health authorities have made great efforts to reach this goal. A continually increasing measles vaccination coverage and other preventive measures have made an impact: no major measles outbreak has been recorded since 2011. In order to evaluate progress towards elimination, measles epidemiology of a previous epidemic period (2007–2011) was compared with the current post-epidemic period (2012–July 2018) by analysis of data from the mandatory notification system. A decrease of 94% in the average annual incidence rate occurred between the two periods (from 133 to 9 cases per million inhabitants). This was accompanied by significant changes in the epidemiology that are expected and characteristic of countries with limited circulation of the measles virus. After analysing the performance of the Swiss surveillance system and the data provided, the WHO concluded that endemic measles transmission was interrupted in Switzerland in 2016 and 2017.

Marked increase in measles vaccination coverage among young adults in Switzerland: a campaign or cohort effect?

OBJECTIVES: To evaluate the impact of the Swiss measles elimination strategy-including a mass media campaign-on vaccination coverage and awareness among young adults aged 20-29 years. METHODS: Comparison of the results of two cross-sectional population surveys in 2012 and 2015. RESULTS: Documented vaccination coverage increased from 77 to 88% for two doses of measles vaccine. Major determinants of complete vaccination were survey year, birth cohort, sex and the absence of prior measles disease. If birth cohort and prior history of measles disease are included as factors in a multivariate model, the difference between 2012 and 2015 vanishes. CONCLUSIONS: The marked increase in complete measles vaccination coverage is due to a cohort effect, owing to the introduction of the second dose of vaccine in 1996. Most of the vaccinations were administered before the national strategy was implemented and vaccination catch-ups did not increase during the campaign in young adults. Nevertheless, this study provides evidence of an improvement in the awareness of measles and measles vaccination in young adults, which may result in an impact on measles vaccination coverage in the near future.

The epidemiology of hepatitis C in Switzerland: trends in notifications, 1988-2015.

With an estimated antibody prevalence of 0.7% in the low-risk population, hepatitis C virus (HCV) endemicity in Switzerland is low. We reviewed data from mandatory hepatitis C surveillance for 1988-2015 in order to describe the evolution of acute HCV infections and newly reported non-acute cases, and their epidemiological features. Crude and stratified annual incidence and notification rates and rate ratios were calculated using Poisson regression. Acute HCV incidence peaked in 2002 at 1.8 cases per 100,000 population, then declined sharply, levelling at around 0.7/100,000 from 2006. Notification rates for non-acute HCV cases peaked in 1999 (38.6/100,000), decreasing to 16.8/100,000 in 2015. Men constituted 65.5% of acute cases and 60.4% of non-acute cases. During the periods 1992-1995 and 2012-2015, the median age of acute cases increased from 28 to 37 and of non-acute cases from 32 to 48 years. The exposure leading to most acute (90.4%) and non-acute (71.9%) cases was presumably in Switzerland. Despite a sharp decrease since 2000, injecting drugs was the main reported exposure for both acute (63.8%) and non-acute (66.6%) cases, with a known exposure, followed by sexual contact with an infected person (18.9% and 10.3% respectively). Among all acute cases, the number of men who have sex with men increased sharply after the mid-2000s, totalling 41 during 2012-2015 (25.7%). Although the HCV epidemic peaked in 2000 - probably as a result of measures to control iatrogenic and percutaneous transmission - Switzerland must maintain prevention and surveillance.

Reduction of acute hepatitis B through vaccina-tion of adolescents with no decrease in chronic hepatitis B due to immigration in a low ende-micity country.

With a hepatitis B prevalence of 0.3%, Switzerland is a country with low endemicity. Unlike most other countries, Switzerland's recommendation for vaccination against hepatitis B has since 1998 focused on adolescents aged 11 to 15 years rather than on infants, in addition to risk groups since 1982. This paper describes the evolution of the incidence of acute hepatitis B virus (HBV) infection and newly reported chronic cases in Switzerland, as well as their epidemiological features, in order to discuss the implications for the control of hepatitis B through vaccination. Data from mandatory notifications by physicians and laboratories between 1988 and 2015 were analysed for acute and chronic HBV infection. Crude and stratified incidence and notification rates (IR, NR), and incidence and notification rate ratios (NRR, IRR) by year were calculated by means of a Poisson regression. Acute HBV incidence peaked in 1992 at 7.5 cases per 100 000 population and subsequently declined by 11% annually (IRR 0.89, p <0.001) to the lowest rate of 0.4/100 000 in 2015. The decrease in incidence accelerated after the introduction of vaccination for adolescents (IRR 0.93, p <0.001 vs 0.91, p <0.001), and was more pronounced in the targeted age groups (IRR 0.90, p <0.001 vs 0.84, p <0.001 for age 15-19 years and IRR 0.92, p <0.001 vs 0.83, p <0.001 for age 20-24). The use of injectable drugs as an assumed source of exposure decreased from 58.1% to 1.9% of all exposures between 1988-1991 and 2012-2015, while sexual contact with an infected person increased from 10.3% to 67.9%. The NR of chronic cases increased until 1995, then stabilised at around 15/100 000. A growing majority of the chronic cases originated abroad (58.4% in 1988-1991 and 82.2% in 2012-2015), and the NR was significantly higher for foreigners than for Swiss nationals (NRR 7.92, p <0.001), especially when compared with the IRR of 1.55 (p <0.001) for acute cases. The introduction of universal vaccination of adolescents combined with vaccination of risk groups and other nonvaccine-related measures has brought acute HBV infection under control in Switzerland. However, the rate of new notifications of chronic HBV infection has remained stable, largely as a result of the immigration of people chronically infected prior to arrival. The burden of disease is thus likely to increase, requiring the strengthening of secondary prevention of chronic HBV infection, in addition to renewed efforts to vaccinate people and their families originating from countries with high endemicity, and persons who frequently change sexual partners.

Birth year distribution in reported hepatitis C cases in Switzerland.

Data of the national hepatitis C virus (HCV) notification system and the Swiss hepatitis C cohort study have been analysed for birth year distribution. Persons born between 1955 and 1974 are disproportionally affected by HCV, accounting for 61% of all reported infections. Over the course of the reporting period from 1988 to 2012, the majority of affected persons were born in the mid-60s and a sharply increasing proportion between 1975 and 1984 (from 0.6 to 19.5%). To enhance the so far insufficient HCV detection rates in Switzerland, additional testing strategies such as birth cohort screening must be further evaluated and discussed.

Prospective nationwide surveillance of hospitalizations due to pertussis in children, 2006-2010.

BACKGROUND: Frequency of pertussis is highly variable from country to country and it depends on multiple factors including case definitions and type of surveillance systems used. Many countries recently reported an increase of pertussis cases especially in infants and adolescents. METHODS: From April 2006 to March 2011, 15-year-old patients hospitalized with suspected or proven pertussis were reported to the Swiss Pediatric Surveillance Unit. Patients with ≥14 days of cough plus paroxysms, whooping or post-tussive vomiting fulfilled the clinical case definition of pertussis. For laboratory confirmation, Bordetella pertussis polymerase chain reaction was offered free of charge. RESULTS: Data were available from 159 of 173 reported cases and 130 (90% of them <12 months old) were eligible including 125 laboratory-confirmed B. pertussis infections. Rates per 100,000 population were 2.6 (<16 years) and 38.8 (<12 months), respectively. Most frequent complications were cyanosis (63%) and sleep disturbance (60%); 35 (27%) patients received intensive care and 1 patient died. Source of infection was known in 79 (61%) patients and was mainly a sibling, parent or both. Most patients were unimmunized (65%) or incompletely immunized (30%). CONCLUSIONS: The high rate of pertussis hospitalization in young infants established in this surveillance project and the incomplete pertussis immunization status in almost all hospitalized patients require further efforts for improvement. In addition, introduction of pertussis immunizations for all adolescents (in 2013), young adults (in 2012) and pregnant women (in 2013) in Switzerland should increase indirect protection of vulnerable newborns and infants too young to be fully immunized.

Prospective pertussis surveillance in Switzerland, 1991-2006.

Pertussis has been monitored in Switzerland since 1991 by the nationwide Swiss Sentinel Surveillance Network (SSSN), consisting of approximately 200 general practitioners, internists and pediatricians representing about 3% of the total primary care physicians of these specialities. SSSN members report patients with cough ≥ 14 days plus either an epidemiological link or characteristic symptoms (paroxysms, whoop, post-tussive vomiting) on a weekly basis to the Federal Office of Public Health. Confirmatory PCR from nasopharyngeal specimens is offered for free. A total of 4992 cases have been reported until 2006. Yearly incidence has dropped from 70 cases per 100,000 inhabitants in 1992 to 40 in 2006, with a single epidemic in 1994-1995 with 280-370 cases/100,000. On average 80% of reported cases were tested by PCR, 24% of these were confirmed as Bordetella pertussis infections. For 2.6% of patients complications were reported, most commonly pneumonia, asthma bronchiale, otitis media, bronchitis and rib fractures. On average, 1.5% of patients were hospitalized. Disease in vaccinated patients was mitigated with less frequent complications (unvaccinated: 5.1%; 3 doses: 3.0%; ≥ 4 doses: 1.7%), hospitalizations (unvaccinated: 3.6%; ≥ 1 dose: 1.1%) and various clinical symptoms compared to unvaccinated patients. Comparing the periods 1991-1996, 1997-2001 and 2002-2006, a shift of pertussis from age group 1-9 years to 10-19 and ≥ 40 years was observed among patients cared for by general practitioners and internists. The benefits of further booster doses in adolescents and/or adults need to be considered.

High genetic diversity of measles virus, World Health Organization European Region, 2005-2006.

During 2005-2006, nine measles virus (MV) genotypes were identified throughout the World Health Organization European Region. All major epidemics were associated with genotypes D4, D6, and B3. Other genotypes (B2, D5, D8, D9, G2, and H1) were only found in limited numbers of cases after importation from other continents. The genetic diversity of endemic D6 strains was low; genotypes C2 and D7, circulating in Europe until recent years, were no longer identified. The transmission chains of several indigenous MV strains may thus have been interrupted by enhanced vaccination. However, multiple importations from Africa and Asia and virus introduction into highly mobile and unvaccinated communities caused a massive spread of D4 and B3 strains throughout much of the region. Thus, despite the reduction of endemic MV circulation, importation of MV from other continents caused prolonged circulation and large outbreaks after their introduction into unvaccinated and highly mobile communities.

A 5-year comparison of performance of sentinel and mandatory notification surveillance systems for measles in Switzerland.

A sensitive, specific and timely surveillance is necessary to monitor progress towards measles elimination. We evaluated the performance of sentinel and mandatory-based surveillance systems for measles in Switzerland during a 5-year period by comparing 145 sentinel and 740 mandatory notified cases. The higher proportion of physicians who reported at least one case per year in the sentinel system suggests underreporting in the recently introduced mandatory surveillance for measles. Accordingly, the latter reported 2-36-fold lower estimates for incidence rates than the sentinel surveillance. However, these estimates were only 0.6-12-fold lower when we considered confirmed cases alone, which indicates a higher specificity of the mandatory surveillance system. In contrast, the sentinel network, which covers 3.5% of all outpatient consultations, detected only weakly and late a major national measles epidemic in 2003 and completely missed 2 of 10 cantonal outbreaks. Despite its better timeliness and greater sensitivity in case detection, the sentinel system, in the current situation of low incidence, is insufficient to perform measles control and to monitor progress towards elimination.

Vaccinated students with negative enzyme immunoassay results show positive measles virus-specific antibody levels by immunofluorescence and plaque neutralisation tests.

BACKGROUND: The prevalence of measles antibodies was investigated by an enzyme immunoassay (EIA) in students aged 14 every year since 1996 in a Swiss municipality. This region has wide measles vaccine coverage (first dose > or = 95%, second dose > or = 65%) without any reported measles outbreaks since 20 years. In 2003 and 2004, in contrast to previous years, surprisingly many negative results (33% and 54%, respectively) were observed. OBJECTIVES: To corroborate the measles antibody values by different methods. STUDY DESIGN: Serum samples from 101 students with known vaccination status were available. Sera with equivocal and negative results obtained by two different EIAs were retested by indirect immunofluorescence test (IFT) and plaque neutralisation test (PNT). RESULTS: Retesting by IFT showed a positive result in 17/21 sera (81%) and retesting by PNT indicated that 46/49 sera (94%) were positive; the three sera with negative PNT result were from unvaccinated individuals. Only 3/96 vaccinated students showed measles antibodies below the putative protective level of 0.2 IU/ml after retesting by PNT. CONCLUSIONS: Negative EIA results should be interpreted with caution in a widely vaccinated population without booster by circulation of wild viruses. Retesting by IFT or PNT is recommended.

Phylogenetic analysis of clinical mumps virus isolates from vaccinated and non-vaccinated patients with mumps during an outbreak, Switzerland 1998-2000.

During the past decade mumps outbreaks have occurred in several European countries with universal vaccination programs probably due to poor efficacy of the Rubini vaccine strain. However, the evolution of vaccine escape mutants has also been considered. A phylogenetic analysis was undertaken on 69 clinical mumps isolates obtained from 39 vaccinated and 22 non-vaccinated mumps cases (and six cases with unknown vaccination status) during an outbreak in 1998-2000. Two major strain clusters (SWI-H, SWI-C) with two subgroups each (SWI-H1/2, SWI-C1/2) were identified, which belonged to genotypes C and H. No association between viral clusters and vaccination status or a specific vaccine strain (Jeryl-Lynn or Rubini) was found. Cluster SWI-C1 occurred more frequently in the Western part of Switzerland (P < 0.001). Isolates causing complicated disease tended to cluster more frequently with SWI-H1 (P = 0.11). Wild-type strains homologous or similar to the Rubini vaccine strain (isolated in Switzerland in 1974) were no longer circulating. Therefore, there was no evidence for vaccine escape mutants. Strain redistribution may have occurred during the past decades. Continuous monitoring of circulating mumps virus populations is needed.

Comparison of the effectiveness of two mumps vaccines during an outbreak in Switzerland in 1999 and 2000: a case-cohort study.

In two recent nation-wide outbreaks of mumps in Switzerland two-thirds of young children with clinical mumps had a history of primary vaccination. On average, measles-mumps-rubella (MMR) vaccination coverage is 80%. Two types of vaccine are commonly used: Jeryl-Lynn and Rubini. The effectiveness of the latter has been questioned in several publications. The authors therefore compared Rubini to Jeryl-Lynn in a case-cohort study. The study included 111 young children with clinical mumps who had been reported to the Swiss Federal Office of Public Health (SFOPH) by primary care physicians of the Swiss Sentinel Surveillance Network (SSSN) between January 1999 and May 2000. Sentinel physicians also sampled 661 children from the same birth cohort as the cases. While we found no evidence for the effectiveness of the Rubini strain, vaccination with the Jeryl-Lynn strain was 70% effective against clinical mumps. Furthermore, children vaccinated with the Rubini strain attended primary health care more frequently with clinical mumps than those who had received Jeryl-Lynn (odds ratio: 2.4; 95% confidence interval (CI): 1.3, 4.7). Restricting the analysis to laboratory confirmed cases increased the odds ratio to 18.4 (95% CI: 2.5, 811.2). Our study confirms the low effectiveness of the Rubini strain vaccine in the field. This vaccine should therefore be considered inappropriate for the control and elimination of mumps and its use should be discontinued. As other vaccines with comparable quality and safety standards and a substantially higher effectiveness are available the MMR vaccination program in Switzerland will not be compromised if the use of Rubini is no longer recommended.