Isolation and Genotyping of Adenoviruses from Wastewater and Diarrheal Samples in Egypt from 2016 to 2020

Human adenoviruses (HAdV) are a prevalent cause of diarrhea in children all over the world. Adenoviral infections are responsible for 2% to 10% of diarrheic cases. A long-term investigation was required to gain better knowledge about the incidence of HAdV in Egypt. Herein, we conducted 5 years of detection, isolation, and genotyping of HAdV in fecal and sewage samples from 2016 to 2020, in Cairo, Egypt using molecular and cell culture assays. Human adenoviruses were identified in 35 of 447 fecal samples (7.8%), but only 53.3% (64/120) of the sewage samples. Children under the age of two had the highest positive rate for HAdV infection (77.1%). Species F of HAdV was the most common prevalent genotype in fecal and sewage samples, at 88.5% and 85.9%, respectively. The most prevalent genotypes detected in fecal samples were HAdV-41 (71.2%), HAdV-40 (17.2%), HAdV-6 (5.7%), and HAdV-1 (5.7%). In contrast, the most common genotypes in sewage samples were HAdV-41 (64%), HAdVs-40 (21.8%), HAdV-6 (7.8%), HAdV-1 (4.7%), and HAdV-2 (1.6%). HAdV was detected in all months of the year, with a peak period for clinical samples from December to February (p < 0.001), which matched Egypt’s rainy season, while the monthly distribution of HAdV in sewage samples remained consistent throughout the year, with no statistically significant peak period. Interestingly, the HAdV-type 41 genotype was the most common genotype during all of the years of this study. Throughout a 5-year period, our work revealed the infection rate, seasonal distribution, virus isolates, and genetic diversity of HAdV infections in environmental and clinical samples in Cairo, Egypt. Non-enteric adenovirus types (1, 2 and 6), as well as enteric adenovirus (41 and 40), may play a key role in gastroenteritis in Egypt.