Mpox outbreak in the Netherlands, 2022: public health response, characteristics of the first 1,000 cases and protection of the first-generation smallpox vaccine.

In early May 2022, a global outbreak of mpox started among persons without travel history to regions known to be enzootic for monkeypox virus (MPXV). On 8 August 2022, the Netherlands reported its 1,000th mpox case, representing a cumulative incidence of 55 per million population, one of the highest cumulative incidences worldwide. We describe characteristics of the first 1,000 mpox cases in the Netherlands, reported between 20 May and 8 August 2022, within the context of the public health response. These cases were predominantly men who have sex with men aged 31-45 years. The vast majority of infections were acquired through sexual contact with casual partners in private or recreational settings including LGBTQIA+ venues in the Netherlands. This indicates that, although some larger upsurges occurred from point-source and/or travel-related events, the outbreak was mainly characterised by sustained transmission within the Netherlands. In addition, we estimated the protective effect of first-generation smallpox vaccine against moderate/severe mpox and found a vaccine effectiveness of 58% (95% CI: 17-78%), suggesting moderate protection against moderate/severe mpox symptoms on top of any possible protection by this vaccine against MPXV infection and disease. Communication with and supporting the at-risk population in following mitigation measures remains essential.

[Monkeypox, a new pandemic?] / Uitbraak van monkeypox: een nieuwe pandemie?

Monkeypox (MPX) is a disease caused by the monkeypox virus. It is a viral zoonotic disease, endemic in Central and West Africa. Human-to-human spread also occurs and is a feature of the current global outbreak. As far as we know, exponential transmission during this outbreak is not related to changed viral characteristics but due to multiple high-risk contacts in a subset of people that have contracted the virus, so far almost exclusively affecting men who have sex with men (MSM). Appropriate public health measures and increased alertness of all health care providers is needed to increase case-finding and decrease transmission. There is a real chance of MPX to become endemic in large parts of the world.

Estimated incubation period for monkeypox cases confirmed in the Netherlands, May 2022.

In May 2022, monkeypox outbreaks have been reported in countries not endemic for monkeypox. We estimated the monkeypox incubation period, using reported exposure and symptom-onset times for 18 cases detected and confirmed in the Netherlands up to 31 May 2022. Mean incubation period was 9.0 [corrected] days (5th-95th percentiles: 4.2-17.3), underpinning the current recommendation to monitor or isolate/quarantine case contacts for 21 days. However, as the incubation period may differ between different transmission routes, further epidemiological investigations are needed.

Incidence and mortality of necrotizing fasciitis in The Netherlands: the impact of group A Streptococcus.

BACKGROUND: Little is known about the exact incidence of necrotizing soft tissue infections. The few incidences reported in international literature are not directly relatable to the Netherlands, or other European countries, due to geographic heterogeneity in causative micro-organisms involved. This resulted in the aim of this study to map the incidence, mortality rate and hospital course of necrotizing fasciitis infections in the Netherlands to gain insight in the incidence of necrotizing fasciitis in the Netherlands and the associated mortality and health care burden. METHODS: This nationwide retrospective database study used three distinct data sources to map the incidence of necrotizing fasciitis in the Netherlands between 2014 and 2019, being data from the Dutch Hospital Data (DHD) foundation, data from Osiris-AIZ, which is a database of notifiable diseases managed by regional Public Health Services (GGD) and the National Institute for Public Health and the Environment (RIVM), and previously published studies on necrotizing fasciitis conducted in the Netherlands. RESULTS: The incidence of necrotizing fasciitis in the Netherlands is estimated to be approximately 1.1 to 1.4 cases per 100,000 person years, which corresponds to 193-238 patients per year. Of all necrotizing fasciitis infections, 34 to 42% are caused by the group A Streptococcus. Annually, 56 patients die as a result of a necrotizing fasciitis infection (mortality of 23-29%) and 26 patients undergo an amputation for source control (11-14%). Patients stay a mean of 6 to 7 days at the intensive care unit and have a mean hospital length of stay of 24 to 30 days. CONCLUSION: The combination of nationwide databases provides reliable insight in the epidemiology of low-incidence and heterogenic diseases. In the Netherlands, necrotizing fasciitis is a rare disease with group A Streptococcus being the most common causative micro-organism of necrotizing fasciitis. The prior Dutch cohort studies on necrotizing fasciitis report slightly higher sample mortality rates, compared to the population mortality. However, necrotizing fasciitis remain associated with substantial morbidity and mortality, risk at amputation and health care burden characterized by prolonged ICU and hospital stay.

Public health response to two imported, epidemiologically related cases of Lassa fever in the Netherlands (ex Sierra Leone), November 2019.

On 20 November 2019, Lassa fever was diagnosed in a physician repatriated from Sierra Leone to the Netherlands. A second physician with suspected Lassa fever, repatriated a few days later from the same healthcare facility, was confirmed infected with Lassa virus on 21 November. Comprehensive contact monitoring involving high- and low-risk contacts proved to be feasible and follow-up of the contacts did not reveal any case of secondary transmission in the Netherlands.

[Tick-borne encephalitis in the Netherlands]. / Teken-encefalitis in Nederland.

Tick-borne encephalitis (TBE) is endemic in South-Scandinavia, Central Europe and Eastern Europe. In 2016 the first patient was reported with TBE virus infection contracted in the Netherlands, in a forested area between Driebergen and Maarn (near Utrecht). At the time, field research did not identify any TBE-positive ticks at the supposed infection site. In the last two years, two patients have been diagnosed with TBE in the Diakonessenhuis Hospital in Utrecht; one patient was bitten by a tick in the Netherlands. This time round, tests on ticks from a different area near Utrecht (the forests around Zeist) did identify TBE-positive ticks. TBE infection is often asymptomatic. However, in a small proportion of patients, disease can develop and there is currently no curative therapy available. An effective vaccine is available. At the moment no vaccination recommendation is issued in the Netherlands. TBE should be considered in patients presenting with fever after a recent tick bite. When neurological symptoms appear, referral to a neurologist is necessary.

Evaluation of the surveillance system for invasive meningococcal disease (IMD) in the Netherlands, 2004-2016.

BACKGROUND: Enhanced surveillance for confirmed cases of invasive meningococcal disease (IMD) was introduced in the Netherlands in 2003, in which reference laboratory data (NRLBM) are linked with notification data (OSIRIS). The quality of surveillance information is important for public health decision making. Our objective was to describe the system and evaluate it for data completeness and timeliness. METHODS: Cases reported in the surveillance system from 2004 to 2016 were included. For the notification data, we used information on serogroup, vaccination status, mortality, and country of infection as indicators for record completeness. Notification times to regional and national level were calculated using the reported dates available in the notification database. RESULTS: A total of 2123 cases were reported in the years 2004-2016, of which 1.968 (93%) were reported by the reference laboratory and 1.995 (94%) in the notification system. Of all cases, 1.840 cases (87%) were reported in both systems and could be linked. The serogroup was known in 86% of the notified cases, and was significantly higher (94%) in the years 2013-2016. Information on vaccination status, mortality and country of infection was available in 88, 99 and 97% of notified cases, respectively. Regional notification of cases occurred within one working day for 86% of cases and 98% were notified nationally within three days. CONCLUSIONS: A well performing IMD surveillance system was demonstrated and serogroup completeness has improved over the years. Underlining the need for reporting to both the clinical and laboratory surveillance system remains important to further improve the overall performance in supporting public health response and vaccination policy.

Successful Use of Advertisement Pictures to Assist Recall in a Food-Borne Hepatitis A Outbreak in The Netherlands, 2017.

This study describes an outbreak investigation of 14 hepatitis A cases in the Netherlands. The hepatitis A virus (HAV) genotype IB sequences in cases were highly similar (459/460 nt). The origin of strains could be narrowed to Bulgaria based on information from EPIS-FWD. As an association with consumption of soft fruit was suspected, a case-control study was initiated using a questionnaire and a list of pictures of soft fruit available at the supermarket chain involved. Twelve out of 13 cases consumed a specific frozen raspberry/blueberry product shown on the list (OR 46.0, 95% CI 5.0-27). In multivariable regression analysis this product was the only risk factor (aOR 26.6, 95% CI 2.0-263). Laboratory analyses could not demonstrate HAV-RNA in batches that had been on the market in the incubation period of patients. Trace back of frozen fruit showed that raspberries had been traded by a producer in Bulgaria. After withdrawal of the product from the supermarket no new cases were reported. Use of advertisement pictures of consumed food was helpful in this investigation. Suspicion of the source was strengthened by data from molecular typing and food trace back activities, underlining the importance of good (inter)national cooperation between public health and food safety organisations.

Outbreak of Salmonella Bovismorbificans associated with the consumption of uncooked ham products, the Netherlands, 2016 to 2017.

In January 2017, an increase in reported Salmonellaenterica serotype Bovismorbificans cases in the Netherlands was observed since October 2016. We implemented a case-control study to identify the source, including all cases after December 2016. Adjusted odds ratios were calculated using logistic regression analysis. We traced back the distribution chain of suspected food items and sampled them for microbiological analysis. Human and food isolates were sequenced using whole genome sequencing (WGS). From October 2016 to March 2017, 54 S. Bovismorbificans cases were identified. Sequencing indicated that all were infected with identical strains. Twenty-four cases and 37 controls participated in the study. Cases were more likely to have consumed ham products than controls (aOR = 13; 95% CI: 2.0-77) and to have shopped at a supermarket chain (aOR = 7; 95% CI: 1.3-38). Trace-back investigations led to a Belgian meat processor: one retail ham sample originating from this processor tested positive for S. Bovismorbificans and matched the outbreak strain by WGS. All ham products related to the same batch were removed from the market to prevent further cases. This investigation illustrates the importance of laboratory surveillance for all Salmonella serotypes and the usefulness of WGS in an outbreak investigation.

Risk factors for gastroenteritis associated with canal swimming in two cities in the Netherlands during the summer of 2015: A prospective study.

Urban canal swimming events are popular in the Netherlands. In 2015, two city canal swimming events took place, in Utrecht (Utrecht Singel Swim, USS) and in Amsterdam (Amsterdam City Swim, ACS). This prospective study characterizes the health risks associated with swimming in urban waters. Online questionnaires were sent to 160 (USS) and 2,692 (ACS) participants, with relatives of participants who did not swim completing the questionnaire as a control. Swimming water specimens and stool specimens of diarrheic participants in the ACS group were analysed. A total of 49% of USS and 51% of ACS swimmers returned their questionnaires. Nine percent of USS swimmers and 4% of non-swimmers reported gastrointestinal complaints (aRR 2.1; 95% CI: 0.3-16), while a total of 31% of ACS swimmers and 5% of non-swimmers reported gastrointestinal complaints (aRR 6.3; 95% CI: 4.1-9.5). AGI risk among ACS participants was directly related to increasing number of mouthfuls of water swallowed. Various norovirus genotypes were detected in five out of seven stool specimens taken from ACS participants and in all three tested ACS water samples. We conclude that the AGI risk among open-water swimmers in urban areas depends on the circumstances around the event. The epidemiological curve, the statistical association between swimming and AGI, and the microbiological evidence for norovirus in stool and water specimens suggest that AGI outbreak after the ACS event was due to water contamination by multiple norovirus strains, which is possibly linked to sewage overflow due to prior heavy rainfall. There is need for more targeted preventive measurements and recommendations for organizers, municipal authorities and participants to prevent this reoccurring in the future.

[Fighting mosquitoes in the Netherlands: risks and control of exotic mosquitoes]. / Muggenbestrijding in Nederland: risico's en bestrijding van exotische muggen.

Mosquitoes play a significant role globally in the transmission of so-called vector-borne diseases. In the Netherlands, native mosquitoes are capable of transmitting infectious disease. This has not resulted in outbreaks of disease over the last 50 years. The establishment of exotic mosquito species could pose risks to public health, especially in the case of the Asian tiger mosquito (Aedes albopictus). Several organisations are working together to prevent the establishment of exotic mosquitoes in the Netherlands. A plan for controlling native mosquito species is also currently being developed.