Rotavirus represents the leading cause of severe childhood gastroenteritis. Every year rotavirus is thought to be responsible for approximately 25 million clinic visits, two million hospital admissions, and more than 800 thousand deaths in children under the age of five globally. Although this disease has a worldwide distribution, most deaths occur in the developing countries.
It is hard to distinguish gastroenteritis caused by rotavirus from other enteric pathogens. Therefore establishing an adequate diagnosis requires testing of fecal specimens with commercially available assays. Still, rotavirus is not routinely sought in patients with gastroenteritis because the results do not alter clinical management, which mostly mainly requires appropriate rehydration therapy.
Medical history and physical examination
The primary objective of history taking and physical examination is to assess whether an affected individual (most often a child) is dehydrated, but also to get some potential insights into the etiology of acute gastroenteritis. Thus, the history should include the duration of illness, urination frequency, the nature of stools, the type of emesis, the presence of fever and the assessment of mental status.
Three principal examination signs for determining dehydration in children are an abnormal skin turgor, abnormal respiratory pattern, as well as prolonged capillary refill time. Different scales are used to assess dehydration, and the one from the Centers for Disease Control and Prevention is most commonly employed. Parental report of the child's symptoms can also aid significantly.
Serum electrolyte measurement is usually not required in children with mild to moderate dehydration. The child’s weight during the illness in comparison with the weight after treatment is used to retrospectively determine the degree of dehydration. Urine specific gravity and blood urea nitrogen measurements are poor markers of dehydration.
Laboratory diagnosis of rotaviral infections is primarily achieved via enzyme immunoassays that involve detection of VP6 group A-specific antigen in diarrheal stools. As an alternative, the immunological detection of this antigen can be achieved through the capture of antigen from feces by anti-VP6-specific antibodies immobilized onto latex, nitrocellulose or nylon.
Although the commercial enzyme immunoassays that are used for rotavirus surveillance are sensitive and specific, regular quality control procedures are required in order to ensure that different laboratories are performing the commercial assay at high proficiency.
Electron microscopy is highly specific for detection of rotavirus with sensitivity comparable to enzyme immunoassays. However, the method is labor-intensive and cumbersome for routine detection of rotavirus in large numbers of stool specimens. Furthermore, expensive instruments and highly trained personnel are needed for optimal results.
Rotaviral double-stranded RNA segments can be detected in clinical specimens via extraction of the viral RNA and subsequent analysis by electrophoresis on a polyacrylamide gel followed by silver staining (since silver ions form a stable complex with nucleic acids).
Human rotavirus shows well defined patterns of gene-segment distribution, which are also known as electropherotypes. The results of electropherotyping correlate with the presence of viruses of a specific group, as shown by using other methods. Consequently, the presence of distinct electropherotype patterns has long been considered diagnostic for the presence of individual rotaviruses.
A plethora of sensitive conventional or real-time reverse-transcription polymerase chain reaction (RT-PCR) methods have been developed based on primers that are specific for different rotavirus genes. These methods have been exceptionally useful in detecting rotavirus in extraintestinal tissues, but also for studying the correlation between disease severity and virus load and the duration of viral shedding in stool.