Overview

Rotavirus mostly affects children under the age of five, causing severe diarrhoea and vomiting. It is a viral "gastroenteritis" agent, which means inflammation of the stomach and intestines. It is the cause of diarrhoea and vomiting. It is so common that almost every child under the age of 5 will or has encountered the disease.¹  Rotavirus is the most common cause of hospitalisation for diarrhoea and vomiting in children. However, with the introduction and integration of the rotavirus vaccine into the regular childhood immunisation schedule, the hospitalisation rate for rotavirus is decreasing. It is being replaced by norovirus.³ The vaccine has been used in the UK since 2013. Severe forms of the disease usually present between 6 months and 2 years. These children are not immunised, and the antibodies they receive from their mothers are depleted.⁴ Although the disease is most common in children under the age of 5, adults and individuals with weakened immune systems can also contract rotavirus. Adults usually catch it from the children they live with. Communal living areas can also be outbreak sites, such as university halls of residence. The diarrhoea known as traveller's diarrhoea is also caused by rotavirus. However, adults do not usually need to be hospitalised, and their symptoms are milder.¹³

What are the common symptoms of the disease?

The most common symptoms are vomiting, watery diarrhoea - usually without blood - and mild fever. It usually lasts from two to eight days. Respiratory symptoms may also occur, either due to rotavirus itself or to another virus that is concurrently present. It might also be worth defining what diarrhoea is. It is an increase in frequency and wateriness. Here are the normal frequencies for babies under 1 year old:

• Breastfed babies: 1-12 times a day
• Newborn formula-fed babies: 1-7 times a day
• 6-12 months: 1-3 times a day
• Over 1 year: same as adults 

It can be more than 20 times a day in patients with rotavirus infection. 

In severe cases, dehydration occurs due to loss of water and electrolytes. If left untreated, this can cause death.⁵ Rarely, neurological symptoms such as seizures may occur. The virus can cause encephalitis.⁶

How does it spread?

It usually spreads from the gut to the mouth, known in the medical world as faecal-oral. Due to poor hand hygiene, toys or food can become contaminated. Another way is through sneezing and coughing on surfaces or water. It can survive in water for weeks. During the COVID-19 pandemic, the number of children affected by rotavirus fell dramatically. This may be explained by the absence of day care and by good hand hygiene.⁷

What about diagnosis?

It is usually difficult to diagnose rotavirus from the clinical presentation alone. The symptoms of diarrhoea and vomiting are vague and can be seen in many illnesses. However, there is no specific antiviral treatment for rotavirus. It is usually treated symptomatically, which means replacing the water and electrolytes lost. Because of the extra cost of the diagnostic test, doctors may decide to treat the same cases without testing.²

How is the test done? 

A stool sample is required for diagnosis. The sample can be collected in bulk from the nappy or from a specimen cup, or from rectal swabs. However, the WHO supports the use of the bulk sample for surveillance, as it is more specific.⁸ It is best to test as early as possible, within 4 days of your first symptoms. It is not logical to test after eight days. If it is not tested immediately, then it should be stored in the freezer. Rotavirus stays alive in colder temperatures. This may go some way to explaining the seasonality of it being much more common during the winter months, from October to February. 

What are the diagnostic methods? 

ELISA (Enzyme-linked Immunosorbent Assay) is one of the most reliable.⁹ ELISA works like a sandwich; commercially produced antibodies bind to the antigens (rotavirus). There is another antibody with a specific function in the sample (it is linked to an enzyme), which allows it to be detected by the machine and means that there is an antigen in the sample.¹⁰ With this method, it is possible to detect the virus even a day before the onset of symptoms. It is very successful in identifying patients who are infected with rotavirus. Out of 100 patients with rotavirus, it successfully diagnosed 94 of them in the first 4 days. 

Immunochromatography (ICT) is another widely used technique. One reason for this is that it does not require any additional complex equipment. The sample is dripped onto the commercial test kit. If rotavirus is present, a second line appears in a few minutes. To illustrate, it is the same principle as pregnancy tests and COVID-19 tests. The test can be carried out next to the patient, and the result can be obtained within 15 minutes. It is very accurate to define the infected people with a positive result and those who are not infected with a negative result.⁹

PCR is the most successful method for detecting the rotavirus genome, but it can be positive long after symptoms have disappeared. Therefore, the positive result may not be as important for clinical diagnosis. PCR is an important diagnostic tool, especially for difficult cases. Although it takes longer than the other methods, it is the most reliable. It also provides the rotavirus genome. There are several subtypes of the virus. The vaccines that are used commercially cover specific types of rotavirus. So PCR may not be the best method for everyday clinical practice or surveillance, but it is probably the most important method for clinical research. As mentioned earlier, the symptoms of diarrhoea and vomiting are vague, and there are many pathogens that cause these symptoms. PCR is also important, for example, to differentiate the cause of the disease, e.g. adenovirus or rotavirus.¹²

Latex agglutination takes between 15 and 60 minutes. The sample is mixed with a solution containing latex beads attached to specific antibodies. If rotavirus is present, these latex beads will agglutinate, i.e. form clusters. This is not a viable method. Most of the time, it fails to identify positive samples.¹¹

Electron microscopy is one possible detection method. However, it requires expensive equipment and is time-consuming. To detect the virus, the viral load in the sample should be quite high (more than 10⁶). This means that if there are smaller numbers of viruses to be detected, it is not sensitive enough to make a correct diagnosis.¹¹

Stool culture is an outdated method that is almost never used in clinical settings for rotavirus. It is only used in research. 

Summary

Rotavirus is a causative agent of diarrhoea and vomiting in children. It was the most common cause of hospitalisation in children with diarrhoea and vomiting. After the introduction of the vaccine in the routine childhood immunisation programme, the number of hospitalisations decreased. However, it is still very common in children under 5 years of age. It is usually a self-limiting illness. This means that although there's no antiviral treatment for rotavirus, the disease will get better over time. The most important thing is to keep the child hydrated. These children can go to the toilet up to 20 times, so they are very vulnerable to electrolyte and water loss. Although the symptoms are not very specific, the doctor may not think it necessary to do a diagnostic test. Because of the lack of antiviral treatment.

However, there are many diagnostic methods available for clinical and/or research purposes. ELISA and immunochromatography are widely used in clinical settings because they are relatively rapid. Immunochromatography is even more widely used because it requires no additional equipment other than the test kit and the doctor's eye. It works similarly to a pregnancy test. If there is a second line, then the patient has rotavirus. PCR is the gold standard test; it usually never fails to detect the virus. But it takes longer. This is why it is usually used in clinical research. Electron microscopy, on the other hand, is not as widely used. It requires expensive equipment and can only identify positive cases after a certain level of viral load. The latex agglutination test is also easy to perform and quick. However, it is less successful in identifying the presence of the virus. Even if there is a negative test result with the latex agglutination test, it is better to double-check it with another test method.