Viral gastroenteritis is a major health problem with significant morbidity and economic consequences. Viral gastroenteritis is caused by a number of viruses, including norovirus, rotavirus, adenovirus, astrovirus, and sapovirus [11].
Our detection rate was exactly equal to the detection rate in Seoul, South Korea, using the same multiplex PCR technique and the same kit [12]. Our results are also in agreement with a study on Egyptian children with gastroenteritis using qualitative PCR, in which viral pathogens were detected in 62%. In another study performed in Egypt, multiplex RT–PCR detected viral pathogens in 57% of samples [13]. In Kyoto, Japan, single-tube multiplex PCR was employed for rapid detection of 10 viruses that cause diarrhoea, with 47.2% of samples being positive for 8 forms of the target viruses. This variation may be attributed to sample size and geographical distribution differences [14].
The most common viruses found in our patients were norovirus G2 and rotavirus, followed by astrovirus and adenovirus. Among norovirus-infected patients, norovirus G2 accounted for 52% (26/50) of the cases, exceeding rotavirus infection. This has been observed in several studies from various countries after implementing rotavirus vaccination [15,16,17]. Our finding is consistent with a systematic review conducted by Kreidieh et al.’s (2018), which included studies from 24 countries in the Middle East and North Africa (MENA) from 2000 to 2015. This review showed that norovirus was considered the second leading cause of gastroenteritis, with an infection rate that ranged from 0.82 to 36.84% in the MENA region [18]. Similarly, in Japan, 57.8% of samples were positive for norovirus [19]. Lower rates were reported in previous studies in Egypt, in which a Qiagen (Hilden, Germany) one-step RT–PCR kit was used. The norovirus detection rate was 26.0%, and the difference in the results may reflect differences in patient characteristics (age 1 month to 18 years) [20].
Group A rotavirus was the second most prevalent virus detected in our study, accounting for 24%. Two Korean studies reported similar detection rates of 24.8% and 26.9% for rotavirus using the same kit [21]; in Iran, rotavirus was detected in 27.0% of cases using RT-PCR [22]. However, higher results were reported in three other studies using RT-PCR for the detection of viruses causing gastroenteritis in Egyptian children, in which detection rates of rotavirus were 37.0%, 39.0% and 57.4%, respectively [13, 20, 23]. This difference in detection rate can be explained by the difference in geographical distribution, as the two studies were performed in Cairo and Banha, in contrast to our study, which was performed in Upper Egypt in Qena and Aswan. The difference in patient characteristics may also be responsible, as the age group of the studied population was from 1 month to 18 years old in the first study and from 1 month to 2 years old in the second. Additionally, there were different numbers of patients in the studies than in our study. Samples were collected from 100 patients in the first study, from 130 patients in the second study, and from 500 patients in the last study. Other studies performed on children admitted to Abo El Reesh Hospital in Cairo University showed higher results, with a 31.0% detection rate for rotavirus with different techniques (enzyme immunoassay kits RIDASCREEN® viralantigen, RBiopharm AG, Germany) and different sample sizes (119 cases) [24].
Adenovirus was detected in 6.0% of cases. Our results are in agreement with results that 6.7% of children with gastroenteritis in Cairo are positive for adenovirus [24]. Other studies used a qualitative test based on using ICT as a screening test for the detection of rotavirus and adenovirus and reported rates of 28.3% and 19.3% [25], with 22% and 3% by another study in Iraq and Sulaimani [26].
Astrovirus was detected in 8.0% of the patients in our study. Our results are in accordance with those of Ahmed et al., 2011, who detected a rate of 6.3% in Abo Homos, Egypt, using RT–PCR [27]. Lower figures were reported in other studies: 5.5% in Lebanon [28], 3.3% by So et al., 2013, in South Korea [21], 3% by El Mohamady et al., 2006, in Al Fayoum, Egypt [29], 1.7% by Rahouma et al., 2011, in Libya [30], and 1.6% by Maham et al., 2013, in Iran [31]; these differences may be related to the larger sample size compared to our study and different geographical distributions.
On the other hand, higher figures were reported in Nigeria by Ayolabi et al., 2012, who reported a rate of 40.4% [32].
Norovirus G1 was not detected in our study, which is in accordance with Kittigul et al., 2009, who reported a rate of 0.8% in Thailand using the same technique [33].
In our study, coinfection with more than one virus was observed in 9/50 (18%) of cases. Lower figures for the rate of coinfection were reported by Khamrin et al., 2011, in Japan (12.8%) [14] and Zaghloul et al., 2013 (10%) [23]. In our study, norovirus G2 was the most prevalent virus associated with coinfection. A similar finding was documented by Kim et al., 2017, in Korea in their study on children with acute gastroenteritis after the introduction of rotavirus vaccination [12]. Coinfection with rotavirus and norovirus was the most common type of coinfection and occurred in 6/9 (66.7%) of cases with mixed infection. Similarly, Zaghloul et al., 2013, reported that coinfection with rotavirus and norovirus in Egypt was most common and occurred in 62.2% of cases in their study [23].
All pathogens identified in our study showed the highest prevalence among children younger than 2 years of age. Faecal-oral contact, ingestion of contaminated water or food and person-to-person contact, the most common modes of transmission, may be the cause, as most of our patients live in rural and urban areas of Qena and Aswan. Additionally, the decreased prevalence of viral gastroenteritis in older children may be due to developed immunity against these viruses causing diarrhoea; the difference may also be due to the behaviour of older children. Norovirus G2 was detected in 50% of the age group less than 1 year, 38.5% of the age group between 13 and 16 months and 11.5% of the age group between 37 and 60 months. This is similar to the distribution in Egypt according to Zaghloul et al., 2013, who reported 35.8% of children infected with norovirus younger than 1 year of age, 38.2% from 1 to 3 years and 13.6% from 3 to 5 years in outpatient clinics at Ain Shams University of Egypt [23]. Additionally, a study in Delhi performed by Gupta et al., 2018, showed that most norovirus-infected children were younger than 1 year old [34]. In our study, 66.7% of rotavirus-infected children were less than 1 year old, 25% were between 13 and 16 months old, and 8.3% were between 37 and 60 months old. Our finding is in accordance with Gupta et al., 2018, in Delhi and Ferreira et al., 2012, in southern Brazil, who showed that most children infected with rotavirus were younger than 2 years old [34, 35]. Fifty percent of astrovirus-infected patients in this study were younger than 1 year old, 25% were between 13 and 16 months old, and 25% were between 37 and 60 months old. This finding was similar to a study in Iran by Maham et al., 2013, who reported that most astrovirus-infected patients were younger than 2 years old [31]. A total of 66.7% of children in our study were infected by adenovirus in the age group less than 1 year, and 33.3% of them were in the group between 13 and 16 months. This finding is in agreement with Filho et al., 2007, who detected 79% of adenovirus-infected cases in children less than 2 years of age [36].
The prevalence of all detected viruses was higher in summer (May to October) than in winter, which is in agreement with other Egyptian studies that found that norovirus, rotavirus, astrovirus and adenovirus were present in 26.5%, 19%, 11.7% and 47% of cases as a single pathogen or co-pathogen, respectively, with seasonal distribution from May to October [37]. In our study, the prevalence of norovirus G2 in warm weather was 57.7% compared to 42.3% in cold weather. Similarly, in Indonesia [38], Thailand [33] and Morocco, norovirus G2 had a peak in summer months [39].
In our study, positive cases of rotavirus were 66.7% in warm weather compared to 33.3% in cold weather. These findings are in agreement with Zagazig University hospitals in Egypt [40]. Although two other studies in Egypt showed that there was no seasonal variation for rotavirus infection, the first study was performed on children in rural areas [41], while the children in the second study were from the Nile River Delta and showed that the peak of rotavirus causing diarrhoea was in late summer and early winter [42]. This difference may be explained by the seasonal nature of rotavirus infections being not universal: in developed countries, the peak season of viral infection is winter in a temperate climate; in developing countries with tropical and subtropical weather, rotavirus is present throughout the year [43].
In our study, all positive cases of adenovirus were reported in summer weather. Modarres et al., 2006, documented that in most parts of the world, adenovirus is present throughout the year [44], regarding astrovirus, most positive cases were reported in warm weather, which is in agreement with El-Mohammady et al., 2012, who detected astrovirus mainly in warm weather y[37].