The Impact of the Extreme Amazonian Flood Season on the Incidence of Viral Gastroenteritis Cases

Dam-mediated flooding impact on outpatient attendance and diarrhoea cases in northern Ghana: a mixed methods study

Background

Floods are the most frequently occurring natural disaster and constitute a significant public health risk. Several operational satellite-based flood detection systems quantify flooding extent, but it is unclear how far the choice of satellite-based flood product affects the findings of epidemiological studies of associated public health risks. Few studies of flooding’s health impacts have used mixed methods to enrich understanding of these impacts. This study therefore aims to evaluate the relationship between two satellite-derived flood products with outpatient attendance and diarrhoeal disease in northern Ghana, identifying plausible reasons for observed relationships via qualitative interviews.

Methods

A convergent parallel mixed methods design combined an ecological time series with focus group discussions and key informant interviews. Through an ecological time series component, monthly outpatient attendance and diarrhoea case counts from health facilities in two flood-prone districts for 2016–2020 were integrated with monthly flooding map layers classified via the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat satellite sensors. The relationship between reported diarrhoea and outpatient attendance with flooding was examined using Poisson regression, controlling for seasonality and facility catchment population. Four focus group discussions with affected community members and four key informant interviews with health professionals explored flooding’s impact on healthcare delivery and access.

Results

Flooding detected via Landsat better predicted outpatient attendance and diarrhoea than flooding via MODIS. Outpatient attendance significantly reduced as LandSat-derived flood area per facility catchment increased (adjusted Incidence Rate Ratio = 0.78, 95% CI: 0.61–0.99, p < 0.05), whilst reported diarrhoea significantly increased with flood area per facility catchment (adjusted Incidence Rate Ratio = 4.27, 95% CI: 2.74—6.63, p < 0.001). Key informants noted how flooding affected access to health services as patients and health professionals could not reach the health facility and emergency referrals were unable to travel.

Conclusions

The significant reduction in outpatient attendance during flooding suggests that flooding impairs healthcare delivery. The relationship is sensitive to the choice of satellite-derived flood product, so future studies should consider integrating multiple sources of satellite imagery for more robust exposure assessment. Health teams and communities should plan spatially targeted flood mitigation and health system adaptation strategies that explicitly address population and workforce mobility issues.

A potential risk assessment tool to monitor pathogens circulation in coastal waters

The present study reports data on a 20 months campaign monitoring enteric viruses (hepatitis A, norovirus, rotavirus, astrovirus, sapovirus, and aichivirus) and bacteria (Salmonella spp.) in seawater. The aim of this work was to assess the potential correlation among the presence of viruses/bacteria and different environmental factors like seasonality, water discharge sources (treated and untreated wastewater, mixed waters and raw water) as well as influence of the Italian lockdown measure against COVID-19 pandemic. Results showed different prevalence of the investigated viruses with values equal to 16 % for norovirus GI, 15.1 % for norovirus GII, followed by 13.8 % for astrovirus, and 13.3 % for sapovirus. Rotavirus was detected in the 8.4 % of samples and aichivirus was detected with the lowest prevalence of 3.5 %. Hepatitis A virus was never identified in the monitoring campaign. Salmonella spp. was detected with a prevalence of 36.6 %. Statistical analysis displayed a high correlation for the two noroviruses simultaneous detection (NGI and NGII) while a lower correlation was found for co-presence of noroviruses with astrovirus, sapovirus or Salmonella spp. A significant decrease of enteric pathogens in seawater was observed during the restrictions period. Results on seasonality highlighted a higher viral prevalence correlated to the wet season for all the pathogens but rotavirus and aichivirus, which instead showed an opposite trend and a higher incidence in the dry season. With respect to discharge typology, some viruses displayed a higher prevalence in treated waters (astrovirus, rotavirus, sapovirus and aichivirus) while the other investigated pathogens (noroviruses and Salmonella spp.) showed a higher prevalence in mixed waters. The main observations of this work were used to define a potential monitoring strategy that could be useful for sanitary Authorities to implement surveillance plans aimed at preventing possible sanitary outbreaks and/or environmental quality deterioration.

Epidemiology of enteric virus infections in children living in the Amazon region

OBJECTIVES

To verify the frequency of viruses causing acute gastroenteritis (AGE) in association with the histo-blood group antigen (HBGA) and Rotarix™ vaccination coverage in children from the Amazon region.

DESIGN

Fecal and saliva samples were collected from children with AGE (n = 485) and acute respiratory infection (ARI) (n = 249) clinical symptoms. Rotavirus A (RVA), norovirus, human adenovirus (HAdV), and sapovirus (SaV) were verified in feces by molecular detection. Saliva samples were used for HBGA phenotyping/FUT3 genotyping. Blood group types, clinical aspects and Rotarix™ RVA vaccination data were recorded.

RESULTS

Norovirus remained the most prevalently detected cause of AGE (38%, 184/485 and ARI 21.3%, 53/249). High HAdV frequencies were observed in AGE children (28.6%, 139/485) and ARI children (37.3%, 93/249). RVA was the third most prevalent virus causing AGE (22.7%, 110/485 and ARI 19.3%, 48/249) and a low RV1 coverage (61%, 448/734) was verified. The SaV frequencies were lower (7.2%, 35/485 for AGE and 6.8%, 17/249 for ARI). Secretor children were HBGA susceptible to HAdV infection (OR 1.5, 95% CI 1.0-2.3; P = 0.04) but not to RVA, norovirus or SaV infection.

CONCLUSIONS

Norovirus could be considered the main etiological agent of AGE. No association was verified for HBGA susceptibility to RVA, norovirus and SaV. Secretor children showed a slight susceptibility to HAdV infection and the Le (a-b-) heterogeneous SNPs on the FUT3 gene.

Seasonal and spatial dynamics of enteric viruses in wastewater and in riverine and estuarine receiving waters

Enteric viruses represent a global public health threat and are implicated in numerous foodborne and waterborne disease outbreaks. Nonetheless, relatively little is known of their fate and stability in the environment. In this study we used carefully validated methods to monitor enteric viruses, namely adenovirus (AdV), JC polyomavirus (JCV), noroviruses (NoVs), sapovirus (SaV) and hepatitis A and E viruses (HAV and HEV) from wastewater source to beaches and shellfish beds. Wastewater influent and effluent, surface water, sediment and shellfish samples were collected in the Conwy catchment (North Wales, UK) once a month for one year. High concentrations of AdV and JCV were found in the majority of samples, and no seasonal patterns were observed. No HAV and HEV were detected and no related illnesses were reported in the area during the period of sampling. Noroviruses and SaV were also detected at high concentrations in wastewater and surface water, and their presence correlated with local gastroenteritis outbreaks during the spring and autumn seasons. Noroviruses were also found in estuarine sediment and in shellfish harvested for human consumption. As PCR-based methods were used for quantification, viral infectivity and degradation was estimated using a NoV capsid integrity assay. The assay revealed low-levels of viral decay in wastewater effluent compared to influent, and more significant decay in environmental waters and sediment. Results suggest that AdV and JCV may be suitable markers for the assessment of the spatial distribution of wastewater contamination in the environment; and pathogenic viruses can be directly monitored during and after reported outbreaks to prevent further environment-derived illnesses.