Overview

Gastroenteritis is a common condition that is an infection of the stomach and the bowel, causing vomiting and diarrhoea. The microorganism causing the infection is either a virus or a bacterium. The most commonly known virus to cause gastroenteritis is “rotavirus”, which is particularly common in young children, however, it can affect people of all ages. Another virus, “norovirus” is encountered more commonly in adults.¹

Rotavirus gastroenteritis

Characteristics of rotavirus

Rotavirus is a common cause of diarrhoea that is widespread in both developing and developed countries. It is most predominant in infants and young children under 5 years of age, especially children between 6 months and 2 years of age, who can spread the infection to their family members and people with close contact as in child care centres. Rotavirus can also spread in hospitals. Rotavirus most commonly infect children during the winter and spring. Adults are also at risk of getting the infection, but usually tend to have milder symptoms unless their immune system is weakened by another pathology.^2,3

There are five types of rotavirus (A, B, C, D, E). Groups A to C are responsible for human infections, and all the groups (A to E) can infect animals.³

Repeated infections with different types of rotavirus are possible and are usually the case in children as they get several episodes of rotavirus infection in their first year of life. The first episode is usually the most severe, as the body starts to build immunity against the virus in later episodes, which also explains why rotavirus infection becomes rare in adults.³

The virus is shed in the stool of infected patients and gets into the environment. Other people can get the virus by either touching contaminated surfaces with their hands and then putting that unwashed hand in their mouth, or eating foods or drinks that are contaminated with the virus, known as feco-oral transmission. Rotavirus can survive for months in stools at room temperature as it is highly resistant to environmental factors. People are more likely to shed the virus and infect others when they are experiencing symptoms and up to 3 days after they recover. In addition, people can also shed the virus before they develop symptoms.²

Clinical presentation of rotavirus gastroenteritis 

The incubation period of rotavirus is usually 2 days, which is the period from getting the virus inside the body until the development of symptoms.² Then infected patients start to develop symptoms of diarrhoea and vomiting, which can be associated with fever, and abdominal pain, and may be complicated by dehydration, particularly in children younger than 2 years of age who may require hospital admission for dehydration–signs of dehydration include reduced amount of urine, dryness of the mouth, reduced tears when crying, sleepiness.² Illness may last about 5-7 days before resolution of symptoms.²

How to diagnose rotavirus gastroenteritis  

Diagnosis of gastroenteritis is usually based on the typical clinical symptoms and history: 

• Clinical symptoms of diarrhoea, vomiting, fever, and abdominal pain
• Personal recent history of contact with contaminated food, drinks, or objects, or history of other family members or close contacts currently having similar symptoms
• A stool sample laboratory test may be used to confirm the diagnosis by detection of the virus antigen in stool

How to treat rotavirus gastroenteritis

• In the majority of cases, the only treatment needed for rotavirus is rehydration with plenty of fluids and bed rest. Drinking adequate amounts of fluid should be encouraged even if the patient is vomiting a small amount. In children, there are commercially available solutions that are usually recommended, known as ‘oral rehydration solutions’. In addition to that, in breastfed babies, mothers are encouraged to continue breastfeeding
• If the vomiting and diarrhoea are prolonged, administering fluid and electrolytes by a cannula into the veins may be indicated
• Some medications may be prescribed in certain conditions to control prolonged diarrhoea, however, this should always be under the doctor's observation
• There is no role in prescribing antibiotics or antiviral medications²

What are the methods of prevention of rotavirus gastroenteritis? 

Hand and food hygiene 

• Good handwashing with soap and clean water (at least for 20 seconds) is the most effective method of prevention. Especially after a bowel movement and before touching foods, and for caregivers, before preparing feeding bottles for their babies, and after changing babies' diapers 
• If no access to water and soap, an antibacterial hand sanitiser can be used
• Avoidance of high-risk foods and beverages, especially those sold by street vendors, especially when travelling

Rotavirus vaccine 

Two vaccines are available, given by mouth, and depending on the type, either 2 or 3 doses are given for infants as part of children's routine vaccines. Type 1 is given at months 2 and 4 of age, and type 2 is given at months 2, 4, and 6 of age.

It has been reported that the infection with rotavirus has been reduced by 80% in the United States since the introduction of the rotavirus vaccine as a part of the routine vaccination schedule.

Bacterial gastroenteritis

Characteristics of bacterial pathogens 

Bacterial gastroenteritis is usually responsible for more severe diarrhoea compared to rotavirus gastroenteritis. The diarrhoea caused by bacteria is either watery and loose or bloody.

The most commonly identified bacterial pathogens are Salmonella, Escherichia coli (E.coli), Vibrio cholerae, Shigella, Yersinia, and Clostridium perfringens.

Bacterial gastroenteritis is most commonly acquired from food, ingestion of contaminated food, and improper handling and processing of food by food-producing factories. Bacterial gastroenteritis is more commonly encountered during warmer weather, compared to viral gastroenteritis, which predominates in winter and cold weather. A special entity of bacterial gastroenteritis is diarrhoea affecting travellers known as “traveller diarrhoea”, pathogens associated with traveller diarrhoea are variable, including Shigella, Campylobacter, and specific types of E.coli. 

Some types of food are usually associated with a higher incidence of certain bacteria:

• Salmonella is typically acquired from chickens, eggs, poultry, and ice cream
• Campylobacter is also usually associated with chicken consumption in the United States and unpasteurised dairy products
• E.coli (Shiga toxin-producing E.coli) is usually associated with beef, sprouts, and salad greens
• Yersinia is typically associated with pork, unpasteurised milk and dairy
• Shigella is usually associated with outbreaks in daycares and is easily transmitted from person to person^4,5

In some conditions, the ingestion of preformed toxins present in the food is responsible for the infection (i.e. not the bacteria itself) and is more commonly acquired from restaurant food: 

• Clostridium perfringens in beef, poultry, and pre-warmed foods
• Bacillus cereus in rice, fried rice, and meats
• Staphylococcus aureus in diverse food vehicles 

Clinical presentation of bacterial gastroenteritis 

Incubation period (hours to days, depending on the bacteria)

The time from getting the infective pathogen to the development of symptoms is different (from hours to days) according to the type of infective bacteria and whether the bacteria itself is causing the infection or the bacterial toxins ingested with contaminated food. 

A shorter incubation period and a rapid onset of illness (typically within hours) are typical with ingestion of preformed toxins present in the food: 

• Clostridium perfringens: between 6 - 24 hours (beef, poultry, and pre-warmed foods)
• Bacillus cereus: between 2 - 12 hours (in rice, fried rice, and meats)
• Staphylococcus aureus: between 30 minutes and up to 8 hours (in diverse food vehicles)

Symptoms 

Similar to the symptoms of viral gastroenteritis: diarrhoea, associated with vomiting, abdominal pain and fever. The symptoms are usually more severe in cases of bacterial gastroenteritis compared to viral gastroenteritis. 

Diarrhoea can be bloody in certain bacterial infections (Campylobacter, Shiga toxin-producing E.coli, Shigella, Yersinia).

Duration of illness

Duration of illness is variable with different types of bacterial pathogens; in general, it is usually a few days up to a week. However, a doctor's review is recommended. 

Diarrhoea associated with Preformed toxins is self-limited and resolves within 24 - 48 hours with supportive treatment of symptoms only. 

How to diagnose bacterial gastroenteritis 

Diagnosis of bacterial gastroenteritis is usually based on the clinical symptoms without the need for further tests. However, certain cases may require further laboratory investigations such as a complete blood count and other blood and stool testing. 

Stool testing is indicated in cases of:

• Severe illness 
• Patients with bloody diarrhoea, or the presence of mucus in diarrhoea 
• Pregnant women
• Patients older than 70 years old 
• Patients with reduced immunity  

The type of stool test is a stool culture that aims to identify the presence of bacteria within a stool sample.

How to treat bacterial gastroenteritis

Supportive treatment 

• Rehydration with oral fluid intake, however, if oral intake is unsuccessful, administration of fluid to the veins through a cannula is indicated 
• Symptomatic treatment for diarrhoea, fever, and pain accordingly–A doctor's advice is needed

Antibiotics therapy 

Antibiotics for certain patients and a doctor's advice is recommended: 

• Specific bacterial pathogens such as Shiga-toxin-producing E.coli 
• Severe illness 
• Patients older than 70 years old
• Patients with reduced immunity 
• Bloody diarrhoea or mucus in stool

What are the complications associated with bacterial gastroenteritis

Dehydration and electrolyte disturbances 

Loss of fluid and electrolytes in stool can cause disturbance in the body, therefore, rehydration and adequate fluid intake are the most essential steps in the management of gastroenteritis. 

Chronic diarrhoea 

Prolonged diarrhoea lasting more than 2 weeks may follow acute gastroenteritis. 

Specific complications with specific pathogens 

These complications are not common but can be encountered in some patients: 

• Hemolytic uremic syndrome (HUS): affects the kidney function and causes hemolysis of red blood cells associated with Shiga toxin-producing E.coli 
• Guillain-Barre syndrome: a neurological complication affects sensation and movement associated with Campylobacter infection
• Reactive arthritis: pain and inflammation in joints associated with Campylobacter, Salmonella, Shigella, and Yersinia infection

Summary 

Gastroenteritis is a common condition affecting people of all ages, most commonly due to viral infection, especially in children, known as “rotavirus”, another cause of gastroenteritis is bacterial infection. Gastroenteritis causes diarrhoea, vomiting, abdominal pain, and fever, symptoms are usually more extensive in the case of bacterial infection. Diagnosis of the condition is usually based on the clinical symptoms, certain additional testing may be indicated in some patients. The most essential step in management is rehydration and fluid replacement to prevent dehydration associated with severe diarrhoea and vomiting. Most cases of gastroenteritis are self-limiting and resolve within a few days to a week.