Pharmaceuticals in natural waters are considered emerging pollutants due to their low concentrations and the negative effects they pose to the environment. Common sources of such pollutants include untreated wastewater from hospitals, residential, industrial, and agricultural sources. Many wastewater treatment methods only remove a subset of all pharmaceuticals from the wastewater; remaining pharmaceuticals are discharged into natural waters, and ultimately drain into coastal areas. Regions without proper wastewater treatment are especially susceptible to such contamination. This study deals with the distribution, sources, and seasonal variability of pharmaceuticals in key aquatic systems in the Philippines. Two watershed continuums (Davao Gulf, Davao City; Macajalar Bay, Cagayan de Oro City); two tourist areas (Boracay Island, Aklan; Mabini, Batangas); and one pristine atoll (Tubbataha Reefs, Palawan)—all with varied prevailing human population pressures—were studied. Samples of hospital wastewater as well as groundwater, surface and bottom water samples from rivers and coastal seas collected during dry and wet seasons were analyzed using solid-phase extraction and liquid chromatography-tandem mass spectrometry. Thirty-four target pharmaceutical residues and antibiotics were extracted and quantified. Acetaminophen was detected at concentrations of up to 289.17 ppb in freshwater samples, and at concentrations of up to 253.39 ppb in seawater samples. Ubiquitous to all the sites was caffeine, reaching 1848.57 ppb. Sulfamethazine, a commonly used veterinary antibiotic, was detected at 764.91 ppb in a river site in Cagayan de Oro. Untreated hospital wastewater contained metformin, iopamidol, sulfamethoxazole, acetylsulfamethoxazole, ciprofloxacin, and azithromycin, but these pharmaceuticals were not detected in other river and coastal waters. Samples collected during the dry season exhibited higher concentrations than those from the wet season, which appears to be related to increase in transient populations from tourism activities as well as dilution. The presence of pharmaceutical residues and antibiotics in these areas and the potential impact on the environment indicate the need for stricter wastewater management measures, particularly in communities located near water bodies. As the results of this study show, such measures might be most beneficial and effective if imposed during dry season and in areas open to tourism.

Over 60 countries have integrated wastewater-based epidemiology (WBE) in their COVID-19 surveillance programs, focusing on wastewater treatment plants (WWTP). In this paper, we piloted the assessment of SARS-CoV-2 WBE as a complementary public health surveillance method in susceptible communities in a highly urbanized city without WWTP in the Philippines by exploring the extraction and detection methods, evaluating the contribution of physico-chemical–anthropogenic factors, and attempting whole-genome sequencing (WGS). Weekly wastewater samples were collected from sewer pipes or creeks in six communities with moderate-to-high risk of COVID-19 transmission, as categorized by the City Government of Davao from November to December 2020. Physico-chemical properties of the wastewater and anthropogenic conditions of the sites were noted. Samples were concentrated using a PEG-NaCl precipitation method and analyzed by RT-PCR to detect the SARS-CoV-2 N, RdRP, and E genes. A subset of nine samples were subjected to WGS using the Minion sequencing platform. SARS-CoV-2 RNA was detected in twenty-two samples (91.7%) regardless of the presence of new cases. Cycle threshold values correlated with RNA concentration and attack rate. The lack of a sewershed map in the sampled areas highlights the need to integrate this in the WBE planning. A combined analysis of wastewater physico-chemical parameters such as flow rate, surface water temperature, salinity, dissolved oxygen, and total dissolved solids provided insights on the ideal sampling location, time, and method for WBE, and their impact on RNA recovery. The contribution of fecal matter in the wastewater may also be assessed through the coliform count and in the context of anthropogenic conditions in the area. Finally, our attempt on WGS detected single-nucleotide polymorphisms (SNPs) in wastewater which included clinically reported and newly identified mutations in the Philippines. This exploratory report provides a contextualized framework for applying WBE surveillance in low-sanitation areas.

Background Over 50 countries have used Wastewater-Based Epidemiology (WBE) and Whole-Genome Sequencing (WGS) of SARS-CoV-2 for monitoring COVID-19 cases. COVID-19 surveillance in the Philippines relies on clinical monitoring and contact tracing, with both having limited use in early detection or prediction of community outbreaks. Thus, complementary public health surveillance methods that can provide community-level infection data faster and using lesser resources must be explored. Objectives This study piloted and assessed WBE and WGS as approaches for COVID-19 surveillance in low-resource and low-sanitation communities in Davao City, Philippines. Methods Weekly wastewater samples were collected from six barangay community sewer pipes or creeks from November to December 2020. Samples were concentrated using a PEG-NaCl precipitation method and analyzed by RT-PCR to detect the SARS-CoV-2 N, RdRP, and E genes. In addition, SARS-CoV-2 RNA-positive samples were subjected to WGS for genomic mutation surveillance. Public data from clinical surveillance were also reviewed to interpret WBE data. Results Twenty-two of the 24 samples (91.7%) obtained from the six barangays tested positive for SARS-CoV-2 RNA. The cycle threshold (Ct) values were correlated with RNA concentration and attack rate. Thirty-two SARS-CoV-2 mutations were detected in WGS, including novel non-synonymous mutations or indels in seven SARS-CoV-2 genes and ten mutations previously reported in the Philippines. Discussion SARS-CoV-2 RNA was detected in community wastewater from the six barangays of Davao City, even when the barangays were classified as having a low risk of COVID-19 transmission and no new cases were reported. Despite the fragmented genome sequences analyzed, our genomic surveillance in wastewater confirmed the presence of previously reported mutations while identifying mutations not yet registered in clinical surveillance. The local context of a community must be considered when planning to adopt WBE and WGS as complementary COVID-19 surveillance methodologies, especially in low-sanitation and low-resource settings.