Abstract
Background
Wastewater-based epidemiology has emerged as a valuable tool for surveilling food- and waterborne disease outbreaks. However, wastewater-based epidemiology remains poorly understood in sub-Saharan Africa. The current study investigated the prevalence of five human enteric viruses and the effect of seasonality on their distribution.
Materials and methods
A twelve-month cross-sectional study was conducted using untreated wastewater. Collected samples were concentrated by polyethylene glycol precipitation and analyzed for molecular detection of Adenovirus, Noroviruses Genotype I, Noroviruses Genotype II, Rotavirus, and Astroviruses using a commercially available Real-Time PCR Bosphore® Gastroenteritis Panel Kit.
Results
Overall, all target viruses were detected, with adenoviruses being the most prevalent at 88.9 % (64/72). Our results revealed the variations in the detection of all these viruses, with detection varying with the change of seasons. Although the difference in detection rates between the rainy and dry seasons did not reach statistical significance in some cases, our results reveal a consistent detection (100 %) across all sampling sites at certain seasons. Adenoviruses exhibited a peak detection period from September to November. Regarding Rotavirus and Norovirus, our findings indicate that they exhibited a peak detection during the short rainy season (March–June), with detection rates of 36.7 % (18/49) and 40.9 % (18/44), respectively.
Conclusion
This study provides the first report on the effect of seasonality on the distribution of enteric viruses in wastewater in Cameroon. Our results highlight the importance of considering seasonal variations when designing public health interventions and demonstrate the usefulness of wastewater-based epidemiology in environmental surveillance.
Keywords: Enteric viruses, Wastewater, Seasonal effect, Molecular detection, Conjunctivitis, Outbreaks, Cameroon
1. Introduction
Enteric viruses represent a significant threat to global public health, causing numerous food- and waterborne disease outbreaks worldwide, particularly in developing countries with poor hygiene practices [[1], [2], [3]]. The high concentration of enteric viruses shed by infected individuals makes wastewater a common reservoir for these pathogens [1,2], with adenovirus, hepatitis A virus, norovirus, rotavirus, enterovirus, and polyomavirus being the most commonly detected in environmental samples [1,2,4].
These viruses are the leading cause of severe gastroenteritis worldwide, particularly affecting infants, young children, and vulnerable populations [5]. Additionally, some of these viruses, such as Human adenoviruses, cause conjunctivitis and respiratory infections [6,7]. Despite the availability of effective vaccines, rotaviruses and hepatitis A continue to circulate globally [8,9] and affect humans and animals [10,11].
Gastroenteritis viruses have been detected in various aquatic environments, including surface and groundwater sources intended for human consumption, marine waters, and treated wastewater effluents worldwide [12,13]. These viruses can be excreted in high concentrations in the faeces of infected individuals [1,13]. These viruses can affect humans and animals. Investigating municipal wastewater samples could be an effective way to understand the distribution of these viruses in communities [14].
However, as in other Central African developing countries, firsthand data on wastewater-based surveillance of outbreaks is limited. In Cameroon, previous studies have highlighted the significant prevalence of various enteric viruses, such as enterovirus, rotavirus, adenovirus, and norovirus, among children and adults. Additionally, studies conducted in Cameroon have revealed the number of deaths among children under five years of age [15,16] epidemiological and/or seasonal fluctuation [17], impact of enteric parasites among HIV-positive patients [18] and the molecular characterization in humans of different age ranges [19] and among fruit bats living in contact with human in Cameroon [20].
Yaoundé, Cameroon's political capital, is affectionately known as the “City of Seven Hills.” The city's climate is characterized by distinct seasonal patterns, with two dry seasons from December to March and from June to August, and two rainy seasons from March to June and from September to November [21]. The city's average temperature is 23.5 °C, ranging from 16 °C to 31 °C depending on the season. The city receives an average of 1747 mm of rainfall per year, and humidity varies significantly throughout the day, ranging from 35 % to 98 %, with an average of 80 % % [22].
Cameroon experiences a variety of intertropical climates, which are influenced by the Harmattan and Atlantic monsoon winds. This diversity makes the country an ideal location for studying climate variability and change. Changes in weather patterns, such as rising temperatures and altered rainfall amounts, can significantly impact the distribution of pathogens in the environment. [23]. In addition, the absence of wastewater treatment plants in Cameroon and limited or nonexistent access to municipal water create an environment conducive to waterborne diseases and infections in the surrounding community. Although the country has conducted environmental surveillance for poliovirus since 2015. [24], Data on wastewater-based epidemiology remains very scarce, and the impact of seasonality on wastewater-based epidemiology remains unknown. The only available study, which was conducted in Cameroon, provides information on the circulation of hepatitis E virus genotype 3a in wastewater [25].
To date, information on the surveillance of gastroenteritis outbreaks in communities using wastewater-based epidemiology is scarce in Cameroon. This study aims to investigate the prevalence of five human enteric viruses and the effect of seasonality on their distribution in untreated wastewater from hospitals, domestic wastewater, and market sites in the Mfoundi Division of Yaoundé, Cameroon.
2. Materials and methods
2.1. Study design and area
A twelve-month cross-sectional study was conducted using untreated wastewater collected from hospital, residential, and market sites in the Mfoundi Division of Yaoundé, located in the Center Region of Cameroon (Fig. 1). The division covers 297 km2 and includes seven districts (Yaoundé I to Yaoundé VII), with an estimated population of 3,525,036 according to the 2010 census. Sampling sites were only done in Yaoundé II, III, V, and VI, which have populations of approximately 238,927, 268,625, 268,828, and 268,072, respectively. [26]. For this study, six wastewater sites were identified and selected based on inadequate sanitation infrastructure and high population density. Three of these sites were residential wastewater systems (Biyem Assi, PAPOSY, and Bonas), one was a hospital (CHUY), and the remaining two were associated with markets (Diderot and Mvog-Ada). (See Fig. 1.)
Fig. 1.
Geographical localization of the sites in the Mfoundi Division, Yaoundé, Cameroon. A: Map of Cameroon; B: Center Region; C: Map of Mfoundi Division.
2.2. Sample collection
For this study, one liter of untreated wastewater (WW) was collected once a month from January to December 2023. To maintain DNA/RNA integrity, each sample was transported in a cold chain (between 4° and 8 °C), divided into two 500 mL aliquots, and stored at −80 °C for further analysis after the 12-month collection period.
2.3. Concentration of wastewater samples
All wastewater samples were concentrated using the two-phase separation method with polyethylene glycol (PEG 6000) and the dextran precipitation protocol, as described in reference [27]. Briefly, 500 mL of wastewater was first centrifuged at 1940g and 4 °C for 30 min. The resulting supernatant was transferred to an Erlenmeyer flask, and the pellets were stored in a refrigerator at 4 °C. Then, the pH of the supernatant was adjusted to neutral (pH 7.0–7.5) using a 1 mol/L NaOH solution. Then, a mixture of 39.5 mL of 22 % dextran, 287 mL of 29 % PEG 6000, and 35 mL of 5 M NaCl solution was added to the flask. The mixture was stirred continuously for one hour using a magnetic stirring rod. The mixture was transferred to a 1L aseptic conical separatory funnel and incubated overnight at 4 °C. The next day, the separating funnel valve was opened, and the lower layer and interphase were slowly collected in a sterile centrifuge tube (extraction volume: 4–10 mL per 0.5L sample). The pellet was resuspended in the interphase, and 20 % chloroform by volume and sterile glass beads were added to the mixture. The mixture was shaken vigorously for 20 min using a conventional horizontal oscillator. Finally, the concentrated solution was centrifuged at 1940g for 30 min, and the upper aqueous phase was collected in a sterile tube. Gentamicin antibiotic was added to the solution, bringing the final concentration to 100 mg/mL [27].
2.4. Total nucleic acids (DNA/RNA) extraction
Total nucleic acids (RNA and DNA) were extracted from 200 μL of concentrated wastewater using DaAn Gene kits according to the manufacturer's instructions (DaAn Gene Co., Ltd., China). Briefly, the wastewater sample (200 μL) was mixed with lysis buffer (400 μL) and incubated at room temperature for 10 min. Then, the mixture was applied to the DNA/RNA binding column, and the bound nucleic acids were washed with wash buffer. The nucleic acids were eluted with 50 μL of elution buffer. If amplified on the same day, the extracted nucleic acid was stored at +4 to +8 °C; otherwise, it was stored at −80 °C before analysis.
2.5. RT-PCR detection of rotaviruses, adenoviruses, astroviruses, and norovirus genotypes I and II
The extracted DNA/RNA was analyzed using the BioRad CFX Real-Time PCR Platform (BioRad, USA). Targeted viruses (adenovirus, rotavirus, astrovirus, norovirus genotypes I and II) were analyzed using the Real-Time PCR Bosphore® Gastroenteritis Panel Kit v1 (Bosphore, Turkey, Anatolia Geneworks), following the manufacturer's instructions. Briefly, the viruses were detected in 25 μL reaction volumes containing 5 μL of the extracted samples, 0.2 μL of the internal control, and either Mix1 (with HEX and Cy5) or Mix2 (with FAM, HEX, and Cy5), depending on the virus being detected. A volume of 25 μL of Superscript III Platinum One-Step with Hot-Start Property was added, following the manufacturer's instructions (Bosphore® Gastroenteritis Panel Kit, Anatolia Geneworks).
Following a reverse transcription step at 50 °C for 15 min and an initial denaturation step at 95 °C for 5 min, 40 cycles of two-step PCR were performed in three parallel reactions targeting five different viruses: 97 °C for 15 s and 60 °C for 60 s.
Fluorescence detection was accomplished using FAM, HEX, Cy5, and Texas Red filters. Texas Red was used as an internal control for the three different mixes, whereas FAM, HEX, and Cy5 were used to detect one of the viruses, depending on the mix used. Mixes 1 and 2 were used. For Mix 1, HEX detects Astrovirus, and Cy5 detects Rotavirus. For Mix 2, HEX detects Norovirus Genotype II, FAM detects Norovirus Genotype II, and Cy5 detects Adenovirus. The quality of the assays was ensured by performing parallel runs of positive, negative, and internal control samples. The results were considered valid if the internal control cycle threshold (Ct) value was positive and less than or equal to 30 (Ct ≤ 30). A positive sample was defined as a Ct value of less than or equal to 40 (Ct ≤ 40), and when only the internal control was detected, the sample was considered negative. The Bosphore Gastroenteritis method allows for the qualitative detection of target viruses, with the Ct value being inversely proportional to the quantity of virus present in each sample.
2.6. Effect of seasonality in enteric viruses circulation in wastewater
The climate data for Yaoundé was extracted from the climatological observation records published by the World Bank Climate Change Knowledge Portal [28], which aggregates data from national and international sources, including the Cameroon National Meteorological Service and the World Meteorological Organization. Daily rainfall data were collected and aggregated to calculate monthly means and accumulation totals, respectively, as described by Ayukekbong et al. [17].
2.7. Statistical analyses
All statistical analyses were performed using IBM SPSS Statistics 25.0 software. Chi-square and Pearson's tests were used to evaluate the relationship between the frequencies of rotavirus, adenovirus, astrovirus, and norovirus GI and GII and the seasons. We used the Shapiro-Wilk test to ensure the data followed a normal distribution. All analyses were considered statistically significant at p values <0.05.
3. Results
3.1. Occurrence of enteric viruses in wastewater and the effect of seasonality
Overall, all five target viruses were detected in a total of 72 wastewater samples. Adenoviruses were the most prevalent, at 88.9 % (64/72), followed by rotaviruses at 68.05 % (49/72) and astroviruses at 61.1 % (44/72) (Table 1).
Table 1.
Summary of virus detection from each site during the dry and rainy seasons.
| Seasons | Rotavirus |
Adenovirus |
Astrovirus |
Norovirus GI (N = 21) | Norovirus GII (N = 34) | |
|---|---|---|---|---|---|---|
| (N = 49) | (N = 64) | (N = 44) | ||||
| Bonas | Short Dry | 1/49 (2.04 %) | 1/64 (1.6 %) | 2/44 (4.54 %) | 1/21 (4.8 %) | 1/34 (3 %) |
| High Dry | 2/49 (4.08 %) | 2/64 (3.13 %) | 2/44 (4.54 %) | 1/21 (4.8 %) | 2/34 (6 %) | |
| Short Rainy | 2/49 (4.08 %) | 1/64 (1.6 %) | 2/44 (4.54 %) | 3/21 (14.3 %) | 5/34 (14.7 %) | |
| High Rainy | 6/49 (12.24 %) | 6/64 (9.4 %) | 5/44 (11.4 %) | 1/21 (4.8 %) | 1/34 (3 %) | |
| Paposy | Short Dry | 1/49 (2.04 %) | 2/64 (3.13 %) | 1/44 (2.3 %) | 1/21 (4.8 %) | 1/34 (3 %) |
| High Dry | 1/49 (2.04 %) | 1/64 (1.6 %) | 1/44 (2.3 %) | 1/21 (4.8 %) | 1/34 (3 %) | |
| Short Rainy | 3/49 (6.12 %) | 3/64 (4.7 %) | 2/44 (4.54 %) | 3/21 (14.3 %) | 4/34 (11.8 %) | |
| High Rainy | 7/49 (14.3 %) | 6/64 (9.4 %) | 7/44 (15.9 %) | 1/21 (4.8 %) | 2/34 (6 %) | |
| Diderot | Short Dry | 1/49 (2.04 %) | 1/64 (1.6 %) | 1/44 (2.3 %) | 0 (0 %) | 0 (0 %) |
| High Dry | 1/49 (2.04 %) | 1/64 (1.6 %) | 1/44 (2.3 %) | 0 (0 %) | 1/34 (3 %) | |
| Short Rainy | 1/49 (2.04 %) | 2/64 (3.13 %) | 1/44 (2.3 %) | 2/21 (9.5 %) | 3/34 (8.8 %) | |
| High Rainy | 3/49 (6.12 %) | 5/64 (7.81 %) | 4/44 (9.1 %) | 1/21 (4.8 %) | 1/34(3 %) | |
| CHUY | Short Dry | 1/49 (2.04 %) | 2/64 (3.13 %) | 1/44 (2.3 %) | 0 (0 %) | 0 (0 %) |
| High Dry | 0 (0 %) | 1/64 (1.6 %) | 1/44 (2.3 %) | 0 (0 %) | 0 (0 %) | |
| Short Rainy | 1/49 (2.04 %) | 2/64 (3.13 %) | 2/44 (4.54 %) | 2 /21 (9.5 %) | 2/34 (6 %) | |
| High Rainy | 2/49 (4.08 %) | 6/64 (9.4 %) | 1/44 (2.3 %) | 0 (0 %) | 1/34 (3 %) | |
| Mvog Ada | Short Dry | 1/49 (2.04 %) | 2/64 (3.13 %) | 1/44 (2.3 %) | 1/21 (4.8 %) | 1/34 (3 %) |
| High Dry | 1/49 (2.04 %) | 1/64 (1.6 %) | 1/44 (2.3 %) | 0 (0 %) | 0 (0 %) | |
| Short Rainy | 5/49 (10.20 %) | 3/64 (4.7 %) | 3/44 (6.8 %) | 2/21 (9.5 %) | 3/34 (8.8 %) | |
| High Rainy | 2/49 (4.08 %) | 6/64 (9.4 %) | 2/44 (4.54 %) | 0 (0 %) | 1/34 (3 %) | |
| Biyem Assi | Short Dry | 1/49 (2.04 %) | 2/64 (3.13 %) | 0 (0 %) | 0 (0 %) | 1/34 (3 %) |
| High Dry | 1/49 (2.04 %) | 1/64 (1.6 %) | 1/44 (2.3 %) | 0 (0 %) | 1/34 (3 %) | |
| Short Rainy | 4/49 (8.16 %) | 2/64 (3.13 %) | 1/44 (2.3 %) | 1/21 (4.8 %) | 1/34 (3 %) | |
| High Rainy | 1/49 (2.04 %) | 5/64 (7.81 %) | 2/44 (4.54 %) | 1/21 (4.8 %) | 2/34 (6 %) |
N = is the total number of positives samples per virus. Short dry Season occurs in July to August, High dry season occurs in December to January, Short rainy season occurs in March to June, High rainy season occurs in September to November.
Regarding the seasonal effect on distribution, all these viruses were detected at least once in each sampling site over two seasons (Fig. 2). Yaoundé is known for its equatorial climate, which features a short dry season from July to August, a high dry season from December to January, a short rainy season from March to June, and a high rainy season from September to November.
Fig. 2.
Occurrence of adenovirus, astrovirus, rotavirus, and norovirus GI/GII and seasonal pattern from January to December 2023. Adenoviruses and astroviruses prevalence correlated with heavy rain (r ≤ 0.05; p < 0.05), and rotaviruses and noroviruses peak prevalence with the short rainy season (r ≥ 0.06; p˃0.05).
Of the 72 samples collected, 38 (52.8 %) were taken during the dry season and 34 (47.2 %) during the rainy season. Despite the limited sample size, our results revealed variations in the detection of these viruses depending on the season. Adenovirus was detected in 28.13 % (18/64) of the samples. Interestingly, the highest detection rate was observed during the rainy season, with 100 % (18/18) of samples testing positive at all six sampling sites from September to November. Rotavirus and norovirus were detected during the short rainy season (March–June) at rates of 36.7 % (18/49) and 40.9 % (18/44), respectively, with p values of 0.052 and 0.032. The astrovirus peak occurred at the beginning of the high rainfall period (August–September), 27 %. 3 % (12/44), See Fig. 2.
Although the difference in detection rates between the rainy and dry seasons was not statistically significant, our findings revealed a weak positive correlation between increased rainfall and the detection of all these viruses. Adenovirus and astrovirus prevalence correlated with heavy rain (r ≤ 0.05; p < 0.05), while rotavirus and norovirus peak prevalence correlated with the short rainy season (r ≥ 0.04; p ≥ 0.05). Our findings highlight not only the high frequency of detection but also the consistent detection across all six sampling sites during the rainy season. These results suggest that the presence of these viruses is not limited to specific sites but rather is a widespread phenomenon during short and intense rainy periods (Fig. 2).
3.2. Occurrence of enteric viruses per selected wastewater site
Interestingly, all five targeted viruses (rotavirus, adenovirus, astrovirus, norovirus genotype I, and norovirus genotype II) were detected. As shown in Fig. 3, the two residential wastewater sites, Bonas and PAPOSY, were the most polluted sites, containing all the targeted viruses at high frequencies, more so than the hospital area. Rotaviruses, adenoviruses, astroviruses, norovirus genotype I, and norovirus genotype II were detected in (11/49) 22 %, (12/64) 18.75 %, (11/44) 25 %, (6/21) 28.57 %, and (9/34) 26.5 % in the Bonas residential site, versus (4/49) 8.16 %, (11/64) 17.2 %, (5/44) 9.09 %, (2/21) 9.52 %, and (3/34) 8.82 % in the hospital area. Eighty-two percent were in the hospital site (CHUY) (p = 0.031), or 20.4 %, 18.75 %, 20.5 %, 28.57 %, and 23.52 % were in the residential site (PAPOSY), versus 8.16 %, 17.2 %, 9.09 %, 9.52 %, and 8.82 % in the hospital site (CHUY) (p = 0.033), suggesting higher pollution levels in the surrounding areas of these two sites.
Fig. 3.
Prevalence of adenovirus, astrovirus, rotavirus, and norovirus genotype I and genotype II in the Mfoundi Division, Yaounde, Cameroon, per site.
4. Discussion
This is the first study to determine the prevalence of five gastroenteritis viruses in Cameroonian wastewater and how seasonal variations affect their distribution over a year. To our knowledge, this is the first study of its kind in the Central African region [13].
Various areas of the world have highlighted a close relationship between the prevalence of several pathogens in environmental wastewater and the development of outbreaks in communities [13]. The high prevalence of enteric viruses in this study is consistent with previous studies of Cameroonian children and adults with gastroenteritis [[15], [16], [17]], as well as with studies of patients with gastroenteritis in other sub-Saharan African and South Asian countries [29].
A similar study of raw wastewater in Yaoundé and Douala, Cameroon, reported a higher prevalence of polioviruses [24] and the circulation of hepatitis E virus genotype 3a in untreated wastewater in the northern part of the country [25]. The current study's high prevalence of adenoviruses, rotaviruses [30], and Astroviruses [32,33] in untreated or raw wastewater samples is similar to that reported in several other studies [13,31,32,34]. However, our detection prevalence is higher than that reported in studies of raw and treated wastewater in Egypt (33 % and 20 %, respectively) [35] and of irrigation wastewater sampled from urban and peri-urban areas in Ouagadougou (5.9 %) [36].
Additionally, the present study revealed a significant detection of all these gastroenteritis viruses in wastewater from residential and market areas compared to wastewater from hospitals. As we found, rotavirus, adenovirus, astrovirus, norovirus genotype I, and norovirus genotype II were more prevalent in residential wastewater from Bonas (22 %, 18.75 %, 25 %, 28.57 %, and 26.5 %, respectively) than in the CHUY hospital site (8 %)., 17.2 %, 9.09 %, 9.52 %, and 8.82 %, respectively; p = 0.031). These viruses were also detected in residential wastewater from PAPOSY (20.4 %, 18.75 %, 20.5 %, 28.57 %, and 23.52 %, respectively; p = 0.033). This difference in detection may be due to the complexity of hospital wastewater, which consists of a mixture of disinfectants, pharmaceuticals, chemicals, viruses, and other pathogens [37]. This difference in detection may also be due to the high population density of the communities, the types of activities conducted there, and the higher pollution levels in the surrounding residential areas compared to those of the hospital population [38].
Due to its lack of wastewater treatment plants and limited access to municipal water, Cameroon provides a unique environment for potential sources of waterborne disease and infection in the surrounding community [13]. The high prevalence of enteric viruses in Yaoundé's wastewater indicates frequent virus shedding by the surrounding community. This suggests that water may be an important route of enteric virus transmission in Cameroon. Our findings underscore the importance of ongoing, nationwide wastewater surveillance to monitor gastroenteritis outbreaks.
Interestingly, the present study observed a significant positive correlation between cumulative rainfall and adenovirus prevalence. The peak prevalence of adenovirus detection occurred from September to November (18/64), reaching 28.1 % during the high rainy season and 100 % across all sites during this period. Notably, this adenovirus circulation peak corresponds with Cameroon's peak rainy season in 2023 and coincides with the 2023 conjunctivitis outbreaks in Cameroon and China. [39]. Our findings are consistent with previous research from Venezuela [40] and Egypt [41]. These data contribute to our understanding of the epidemiology of adenovirus circulation in Cameroonian communities and could be valuable for preventing and managing gastroenteritis outbreaks.
The significant positive correlation between cumulative rainfall and the prevalence of Adenovirus detection in our study suggests that rainfall plays a crucial role in the transmission dynamics of Adenoviruses in Cameroon. These findings are consistent with previous research from Venezuela [42], highlighting the importance of enhanced surveillance and preparedness during periods of high rainfall in Cameroon.
This is the first study to monitor the seasonal prevalence of norovirus genotypes I and II in wastewater in Cameroon, and to our knowledge, it is the first study of its kind in the Central African region. The present study also observed norovirus circulation throughout the year, peaking at the beginning of the short rainy season from March to June (36.7 %). Our observation of the norovirus circulation peak in Cameroon is consistent with the available clinical samples from adults and children [17]. Our results align with previous reports from Brazil (33.9 %) [43] and the literature [44]. However, they contradict the typical winter peak observed in numerous studies conducted in temperate regions of the North [45]. Our data show a sharp increase in norovirus prevalence, which is dominated by GII.
In the present study, noroviruses (GI and GII) were significantly detected at the beginning of the short rainy season. Our data on the predominance of GII norovirus are consistent with previous reports demonstrating that GII norovirus is the predominant strain worldwide. However, our results contrast with those of a 2014 study by Ayukekbong et al., which found that GI was highly prevalent. Our results confirm that both GI and GII noroviruses are stable in the environment. Abundant rainfall likely washes wastewater and household waste into the environment, thereby favoring norovirus transmission in communities.
Regarding rotaviruses, our study showed that the peak prevalence coincided with the short rainy season (March–June) at 36.7 %. The high detection rate and peak prevalence of rotavirus observed during the rainy season are consistent with existing clinical data from children under five years old and adults in Cameroon [17], Egypt [46], and N'Djamena [47]. Studies from various regions have reported similar seasonal patterns, with rotavirus infections peaking during rainy and cold or winter seasons.
Notably, the absence of a detectable virus does not necessarily indicate an absence of rotavirus circulation during that time. In Cameroon, the rotavirus vaccine (Rotarix) was introduced in March 2014. The high prevalence of rotavirus in untreated wastewater samples could be attributed to excretion of the vaccine [15], since it is a live, attenuated vaccine [48] containing a combination of human and animal rotaviruses [49]. However, further investigation is needed to understand the relationship between rotavirus vaccine distribution and peak rotavirus detection in wastewater, considering factors such as vaccine coverage, virus shedding, and environmental factors influencing virus survival.
Additionally, the high prevalence of rotavirus during this period suggests that it is highly contagious and easily transmitted at this time. Furthermore, it suggests that rainfall may contribute to increased waterborne exposure [50]. Our findings suggest that increased rainfall may contribute to greater waterborne exposure. This is consistent with previous findings in wastewater, in which rotaviruses were predominantly detected during rainy [51] and cold [52] seasons. Similarly, astrovirus circulation was observed throughout the year, peaking at the beginning of the heavy rainy season, from August to September. This is the first comprehensive, prospective study of astroviruses in Cameroon. Our observations align with other surveys but contrast with findings in the Republic of Congo among young children [53]. Our data demonstrate an increase in astroviruses in wastewater and suggest that these viruses are highly stable in the environment.
A national surveillance program for these viruses is crucial for effectively controlling and preventing infections [54]. The current study's findings are limited by the absence of clinical data. However, the detection of these viruses in wastewater suggests that multiple individuals in the population are likely infected and that the viruses are circulating within the community. A previous study in Cameroon analyzed clinical samples and reported high prevalence rates of enteroviruses, noroviruses, and astroviruses among children and adults with acute gastroenteritis during the rainy season [17]. These results suggest a potential correlation between clinical and environmental detection, which highlights the impact of environmental pollution on the health of people in this region.
Currently, there is a lack of epidemiological data on the prevalence of gastroenteritis viruses among asymptomatic individuals in Cameroon. Monitoring raw wastewater could provide valuable insights into the true prevalence of viral infections in surrounding areas because it contains viruses shed by people with both symptomatic and asymptomatic cases of acute diarrhea. Additionally, analyzing wastewater for enteric viruses can serve as an early warning system for predicting viral gastroenteritis outbreaks.
5. Conclusion
This study is the first to report on the effect of seasonality on the distribution of enteric viruses in Cameroonian wastewater. Our results demonstrate the effectiveness of using wastewater matrices to monitor enteric viruses in the environment and the risk of acute gastroenteritis in Cameroon. They also underscore the importance of considering seasonal variations when designing public health interventions and demonstrate the usefulness of wastewater-based epidemiology in community environmental surveillance. These data provide valuable information to alert healthcare providers when a peak infection period is likely to occur in the community. Leveraging wastewater surveillance can enhance Cameroon's ability to prevent and manage outbreaks, strengthen its One Health approach, and ultimately reduce the burden of gastroenteritis outbreaks on communities while improving public health outcomes. Future studies, such as two years of surveillance of environmental and clinical samples with phylogenetic analysis, are needed to better understand the epidemiology of these viruses in Cameroon.
CRediT authorship contribution statement
Marie Atsama-Amougou: Writing – review & editing, Writing – original draft, Validation, Methodology, Investigation, Data curation, Conceptualization. Dowbiss Djomsi-Meta: Writing – review & editing, Validation, Methodology, Formal analysis. Modeste Romuald Ngamaleu: Writing – review & editing, Software, Methodology, Funding acquisition, Data curation. Fredy Brice Nemg Simo: Writing – review & editing, Methodology, Investigation, Data curation. Christophe Lontsi Saha: Writing – review & editing, Supervision, Software, Data curation. Nadine Lamare-Boutgam: Writing – review & editing, Validation, Methodology, Formal analysis. Celestin Godwe: Writing – review & editing, Validation, Software. Martin Maidadi-Foudi: Writing – review & editing, Validation, Resources, Formal analysis. Marcel Tongo: Writing – review & editing, Validation, Project administration. Etienne Mpabuka: Writing – review & editing, Writing – original draft, Validation, Methodology, Data curation. Charles Kouanfack: Writing – review & editing, Visualization, Validation, Project administration. Ahidjo Ayouba: Writing – review & editing, Project administration, Investigation, Conceptualization.
Funding sources
This research did not receive any external funding.
Declaration of competing interest
All the authors declare that they have no competing interests.
Acknowledgments
We would like to thank all the staff of the Mfoundi Division for their participation in the study sites identification and the workers who have been involved in wastewater samples collection.
Glossary
- Wastewater-based epidemiology
The study of wastewater to monitor the presence and spread of diseases in a community.
- Enteric viruses
Viruses that affect the gastrointestinal tract, including rotavirus, norovirus, adenovirus, and astrovirus.
- Adenovirus
Adenovirus is a type of virus that can cause a range of illnesses, including gastroenteritis, conjunctivitis, and respiratory infections.
- Astrovirus
Is a virus that can cause gastroenteritis, especially in children and older adults.
- Conjunctivitis
An eye infection that can be caused by adenovirus.
- Gastroenteritis
An inflammation of the stomach and intestines, often caused by enteric viruses.
- Norovirus
A type of virus that can cause gastroenteritis, often spread through contaminated food and water.
- Polyethylene glycol (PEG) precipitation
A method used to concentrate viruses in wastewater samples.
- RT-PCR (Real-Time Polymerase Chain Reaction)
A laboratory technique used to detect and quantify viruses in wastewater samples.
Footnotes
Supplementary data to this article can be found online at https://doi.org/10.1016/j.onehlt.2025.101110.
Appendix A. Supplementary data
Supplementary material 1
Supplementary material 2
Supplementary material 3
Data availability
Data will be made available on request.
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Data Availability Statement
Data will be made available on request.