High Infection Secondary Attack Rates of Severe Acute Respiratory Syndrome Coronavirus 2 in Dutch Households Revealed by Dense Sampling.

BACKGROUND: Indoor environments are considered one of the main settings for transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Households in particular represent a close-contact environment with high probability of transmission between persons of different ages and roles in society. METHODS: Households with a laboratory-confirmed SARS-CoV-2 positive case in the Netherlands (March-May 2020) were included. At least 3 home visits were performed during 4-6 weeks of follow-up, collecting naso- and oropharyngeal swabs, oral fluid, feces and blood samples from all household members for molecular and serological analyses. Symptoms were recorded from 2 weeks before the first visit through to the final visit. Infection secondary attack rates (SAR) were estimated with logistic regression. A transmission model was used to assess household transmission routes. RESULTS: A total of 55 households with 187 household contacts were included. In 17 households no transmission took place; in 11 households all persons were infected. Estimated infection SARs were high, ranging from 35% (95% confidence interval [CI], 24%-46%) in children to 51% (95% CI, 39%-63%) in adults. Estimated transmission rates in the household were high, with reduced susceptibility of children compared with adolescents and adults (0.67; 95% CI, .40-1.1). CONCLUSION: Estimated infection SARs were higher than reported in earlier household studies, presumably owing to our dense sampling protocol. Children were shown to be less susceptible than adults, but the estimated infection SAR in children was still high. Our results reinforce the role of households as one of the main multipliers of SARS-CoV-2 infection in the population.

Identified micro-organisms in hospitalized community-acquired pneumonia patients living near goat and poultry farms.

BACKGROUND: In the Netherlands, an increased risk of community-acquired pneumonia (CAP) has been reported for adults living near goat and poultry farms. Previous results of respiratory microbiome studies in hospitalized CAP patients near poultry farms suggested a higher relative abundance of Streptococcus pneumoniae. This retrospective study, using routine laboratory data from hospitalized CAP patients, aims to explore possible aetiologic micro-organisms of CAP in relation to livestock exposure. METHODS: Patient characteristics and PCR and urinary antigen test results were retrieved retrospectively from electronic medical records of CAP patients admitted to the Jeroen Bosch Hospital or Gelre Hospital in the Netherlands during 2016-2017. Distances between the patients' home address and the nearest poultry and goat farm were calculated. Differences in laboratory test results between CAP patients with and without goat or poultry farms within 2 km of their home address were analyzed using Fisher's exact test. RESULTS: In total, 2230 CAP episodes with diagnostic results were included. In only 25% of the CAP episodes, a micro-organism was detected. A positive urinary antigen test for S. pneumoniae was found more often in patients living within two kilometers of goat (15.2% vs. 11.3%) and poultry farms (14.4% vs. 11.3%), however these differences were not statistically significant (p = 0.1047 and p = 0.1376). CONCLUSION: Our retrospective analysis did not show statistically significant differences in the identified micro-organisms in hospitalized CAP patients related to livestock farming. The study was hampered by limited statistical power and limited laboratory results. Therefore, the potential increased CAP risk around goat and poultry farms will be further explored in a prospective study among CAP patients in primary care.

Use of Antibiotics among Residents Living Close to Poultry or Goat Farms: A Nationwide Analysis in The Netherlands.

Prior regional studies found a high risk of pneumonia for people living close to poultry and goat farms. This epidemiological study in the Netherlands used nationwide antibiotic prescription data as a proxy for pneumonia incidence to investigate whether residents of areas with poultry and goat farms use relatively more antibiotics compared to areas without such farms. We used prescription data on antibiotics most commonly prescribed to treat pneumonia in adults and livestock farming data, both with nationwide coverage. Antibiotic use was expressed as defined daily doses per (4-digit Postal Code (PC4) area)-(age group)-(gender)-(month) combination for the year 2015. We assessed the associations between antibiotic use and farm exposure using negative binomial regression. The amoxicillin, doxycycline, and co-amoxiclav use was significantly higher (5-10% difference in use) in PC4 areas with poultry farms present compared to areas without, even after adjusting for age, gender, smoking, socio-economic status, and goat farm presence. The adjusted models showed no associations between antibiotic use and goat farm presence. The variables included in this study could only partly explain the observed regional differences in antibiotic use. This was an ecological study that precludes inference about causal relations. Further research using individual-level data is recommended.

[The role of children in the transmission of SARS-CoV-2]. / De rol van kinderen in de transmissie van SARS-CoV-2.

OBJECTIVE: To determine whether children play a role in the transmission of SARS-CoV-2 to other children and adults, and to gain insight into symptomatic and asymptomatic infections in children. DESIGN: Analysis of national COVID-19 notifications and prospective observational study in families with children. METHOD: Information about COVID-19 patients and their contacts was obtained from the registration systems used by the public health services. In an ongoing study, patients with COVID-19 were asked to participate if they have a family with children. On two occasions nose-throat swabs and blood were collected for PCR analysis and determination of antibodies against SARS-CoV-2. RESULTS: The notifications suggest that transmission finds place mainly between adults and to a lesser extent between parents and children. For the family study, data were available from 54 households with a total of 227 participants. In families of a confirmed COVID-19 patient, children between 1 and 11 years were less often positive in PCR and serology than older children and adults. CONCLUSION: The study gives no indications that children play an important role in the transmission of SARS-CoV-2. Children can indeed become infected, but transmission mainly takes place between adult peers and from adult family members to children. Transmission among children or from children to adults, as is known in influenza, appears to be less common. Ongoing studies should provide important information for further decision-making on control measures, such as closure of schools.

Animal sources for zoonotic transmission of psittacosis: a systematic review.

BACKGROUND: Human psittacosis, caused by Chlamydia (C.) psittaci, is likely underdiagnosed and underreported, since tests for C. psittaci are often not included in routine microbiological diagnostics. Source tracing traditionally focuses on psittacine pet birds, but recently other animal species have been gaining more attention as possible sources for human psittacosis. This review aims to provide an overview of all suspected animal sources of human psittacosis cases reported in the international literature. In addition, for each animal species the strength of evidence for zoonotic transmission was estimated. METHODS: A systematic literature search was conducted using four databases (Pubmed, Embase, Scopus and Proquest). Articles were included when there was mention of at least one human case of psittacosis and a possible animal source. Investigators independently extracted data from the included articles and estimated strength of evidence for zoonotic transmission, based on a self-developed scoring system taking into account number of human cases, epidemiological evidence and laboratory test results in human, animals, and the environment. RESULTS: Eighty articles were included, which provided information on 136 different situations of possible zoonotic transmission. The maximum score for zoonotic transmission was highest for turkeys, followed by ducks, owls, and the category 'other poultry'. Articles reporting about zoonotic transmission from unspecified birds, psittaciformes and columbiformes provided a relatively low strength of evidence. A genotypical match between human and animal samples was reported twenty-eight times, including transmission from chickens, turkeys, guinea fowl, peafowl, pigeons, ducks, geese, songbirds, parrot-like birds and owls. CONCLUSIONS: Strong evidence exists for zoonotic transmission from turkeys, chickens and ducks, in addition to the more traditionally reported parrot-like animal sources. Based on our scoring system, the evidence was generally stronger for poultry than for parrot-like birds. Psittaciformes should not be disregarded as an important source of human psittacosis, still clinicians and public health officials should include poultry and birds species other than parrots in medical history and source tracing.

Prevalence and Characterization of Heterogeneous Variable-Number Tandem-Repeat Clusters Comprising Drug-Susceptible and/or Variable Resistant Mycobacterium tuberculosis Complex Isolates in the Netherlands from 2004 to 2016.

The variable-number tandem-repeat (VNTR) typing method is used to study tuberculosis (TB) transmission. Clustering of Mycobacterium tuberculosis isolates with identical VNTR patterns is assumed to reflect recent transmission. Hence, clusters are thought to be homogeneous regarding antibiotic resistance. In practice, however, heterogeneous clusters are also identified. This study investigates the prevalence and characteristics of heterogeneous VNTR clusters and assesses whether isolates in these clusters remain clustered when subjected to whole-genome sequencing (WGS). In the period from 2004 to 2016, 9,072 isolates were included. Demographic and epidemiological linkage data were obtained from the Netherlands Tuberculosis Register. VNTR clusters were defined as homogeneous when isolates shared identical resistance profiles or as heterogeneous if both susceptible and (variable) resistant isolates were found. Multivariate logistic regression analysis was performed to identify factors associated with heterogeneous clustering. Isolates from 2016 were subjected to WGS, and a genetic distance of 12 single nucleotide polymorphisms (SNPs) was used as the cutoff for WGS clustering. In total, 4,661/9,072 (51%) isolates were clustered into 985 different VNTR clusters, of which 217 (22%) were heterogeneous. Patient characteristics associated with heterogeneous clustering were non-Dutch ethnicity (odds ratio [OR], 1.46 [95% confidence interval {CI}, 1.22 to 1.75]), asylum seeker (OR, 1.51 [95% CI, 1.24 to 1.85]), extrapulmonary TB (OR, 1.26 [95% CI, 1.09 to 1.46]), previous TB diagnosis (OR, 1.38 [95% CI, 1.04 to 1.82]), and not being a contact of a TB patient (OR, 1.35 [95% CI, 1.08 to 1.69]). With WGS, 34% of heterogeneous and 78% of homogeneous isolates from 2016 remained clustered. Heterogeneous VNTR clusters are common but seem to be explained by a substantial degree of false clustering by VNTR typing compared to WGS.