Systematic literature review and meta-analysis on preventing and controlling norovirus outbreaks on cruise ships, 1990 to 2020: calling for behaviour change strategies of travellers.

BackgroundOutbreaks of norovirus gastroenteritis aboard cruise ships may affect a large number of people, debilitate vulnerable travellers, disrupt vacations and cause economic losses to the cruise ship industry.AimWe aimed to identify risk factors for norovirus outbreaks on cruise ships and assess the effectiveness of prevention and control measures.MethodsWe conducted a systematic literature review searching PubMed and Scopus databases as well as grey literature for articles and reports describing norovirus outbreaks on cruise ships between 1990 and 2020. We also performed a meta-analysis of norovirus prevalence in passengers and crew members.ResultsData from 45 outbreaks on 26 cruise ships from 1990 to 2020 were identified in 13 articles and five reports, with a weighted average of prevalence (attack rate) for passengers of 7% (95% confidence interval (CI): 5.00-9.00) and for crew of 2% (95% CI: 0.00-3.00). Person-to-person was the most frequent mode of transmission in 35 of the 45 outbreaks (in 14 the only mode and in 21 as part of multiple transmission routes). Having an ill cabin mate (OR = 38.70; 95% CI: 13.51-110.86) was the most common risk factor. Six outbreak investigations reported poor hygiene, while four reported satisfactory hygiene in the cruise setting. Behavioural risk factors among travellers were investigated in three of the 13 studies.ConclusionsThe findings indicate a need for behavioural interventions to improve personal hygiene, symptom reporting and compliance with isolation measures, and for reconsidering current isolation policies where symptomatic and healthy individuals are isolated in the same cabin.

Diagnostic accuracy of multiplex nucleic acid amplification tests for Campylobacter infection: a systematic review and meta-analysis.

Campylobacter infection is one of the most frequently reported foodborne diseases with approximately 230,000 and 1.5 million cases each year in Europe and the USA, respectively. Culture methods are the reference for the diagnosis of Campylobacter infections; however, these methods are complex and time-consuming. Multiplex nucleic acid amplification test is favored due to its rapidity, automatization in the procedure followed and the quick simultaneous testing of numerous foodborne pathogens. The aim of this meta-analysis was to evaluate the accuracy of these tests for the diagnosis of Campylobacter infection. Scopus, Science Direct, PubMed, Web of Science, and Mendeley were searched for peer-reviewed articles. The split component synthesis method with the use of the inverse variance heterogeneity model was chosen for the quantitative meta-analysis. Sensitivity analysis was performed by age category and index test. The literature search found 34 studies involving 28,105 patients with suspected gastroenteritis. The sensitivity and specificity were 95.3% (92.3; 97.1) and 97.1% (95.1; 98.3), respectively, and AUC (area under the curve) was 0.963 (0.947; 0.974). Pediatric patients had a lower sensitivity (87.4, 48.2; 98.1) and higher specificity (99.2, 91.6; 99.9) estimate compared to all ages category (sensitivity 95.3, 91.3; 97.5, specificity 96.7, 93.7; 98.3). Among the various index tests, Seeplex/Allplex and Amplidiag/Novodiag had the lowest estimate for sensitivity (88.9, 73.8; 95.8) and specificity (95.2, 86; 98.4), respectively. BDMax had the highest (sensitivity 98.1, 96.1; 99 and specificity 98.5, 97; 99.3). Multiplex nucleic acid tests showed excellent accuracy and could play an influential role in diagnosing Campylobacter infections.

Cross-Sectional Serosurvey and Factors Associated with Exposure of Dogs to Vector-Borne Pathogens in Greece.

Blood samples from 2620 dogs living in 7 different areas were used for the detection of antibodies against Ehrlichia canis and Borrelia burgdorferi and Dirofilaria immitis antigen. Previously published seropositivity data against Leishmania infantum from the same samples were also used to identify multiple-pathogen seropositivity. The associations between seropositivity against each pathogen and gender, age, utility, hair length, and region of residence were evaluated by multivariate logistic regression analyses. The prevalence of seropositivity against E. canis, B. burgdorferi, and D. immitis was 12.25%, 2.23%, and 5.96%, respectively. Double- and triple-pathogen seropositivity was detected in seven different combinations. Age and region of residence were strongly associated with seropositivity against all pathogens. The association between seropositivity and the area of residence highlights the need for regular testing of dogs for vector-borne pathogens in areas with similar conditions to define control measures.

Mutations in the haemagglutinin protein and their effect in transmission of highly pathogenic avian influenza (HPAI) H5N1 virus in sub-optimally vaccinated chickens.

BACKGROUND: Transmission of highly pathogenic avian influenza (HPAI) viruses in poultry flocks is associated with huge economic losses, culling of millions of birds, as well as human infections and deaths. In the cases where vaccination against avian influenza is used as a control measure, it has been found to be ineffective in preventing transmission of field strains. Reports suggest that one of the reasons for this is the use of vaccine doses much lower than the ones recommended by the manufacturer, resulting in very low levels of immunity. In a previous study, we selected for immune escape mutants using homologous polyclonal sera and used them as vaccines in transmission experiments. We concluded that provided a threshold of immunity is reached, antigenic distance between vaccine and challenge strains due to selection need not result in vaccine escape. Here, we evaluate the effect that the mutations in the haemagglutinin protein of our most antigenically-distant mutant may have in the transmission efficiency of this mutant to chickens vaccinated against the parent strain, under sub-optimal vaccination conditions resembling those often found in the field. METHODS: In this study we employed reverse genetics techniques and transmission experiments to examine if the HA mutations of our most antigenically-distant mutant affect its efficiency to transmit to vaccinated chickens. In addition, we simulated sub-optimal vaccination conditions in the field, by using a very low vaccine dose. RESULTS: We find that the mutations in the HA protein of our most antigenically-distant mutant are not enough to allow it to evade even low levels of vaccination-induced immunity. DISCUSSION: Our results suggest that - for the antigenic distances we investigated - vaccination can reduce transmission of an antigenically-distant strain compared to the unvaccinated groups, even when low vaccine doses are used, resulting in low levels of immunity.

Role of vaccination-induced immunity and antigenic distance in the transmission dynamics of highly pathogenic avian influenza H5N1.

Highly pathogenic avian influenza (HPAI) H5N1 epidemics in poultry cause huge economic losses as well as sporadic human morbidity and mortality. Vaccination in poultry has often been reported as being ineffective in preventing transmission and as a potential driving force in the selection of immune escape mutants. We conducted transmission experiments to evaluate the transmission dynamics of HPAI H5N1 strains in chickens vaccinated with high and low doses of immune escape mutants we have previously selected, and analysed the data using mathematical models. Remarkably, we demonstrate that the effect of antigenic distances between the vaccine and challenge strains used in this study is too small to influence the transmission dynamics of the strains used. This is because the effect of a sufficient vaccine dose on antibody levels against the challenge viruses is large enough to compensate for any decrease in antibody titres due to antigenic differences between vaccine and challenge strains. Our results show that at least under experimental conditions, vaccination will remain effective even after antigenic changes as may be caused by the initial selection in vaccinated birds.