Infectious diseases involving the stomach, and often extending to neighboring sections of the alimentary tract (esophagus and small intestine), may be caused by a number of pathogens, including viruses, bacteria, fungi and other parasites. Viral infections may cause gastroenteritis (frequent) or gastritis (rare). The term ‘stomach virus’ is more frequently used to describe viral gastroenteritis, which is a common infection globally and known by many common names including the stomach flu, stomach bug and gastric flu.
Other viral diseases that may affect the stomach are rare. Certain autoimmune conditions affecting the stomach and other parts of the alimentary tract may have been triggered by a viral infection, although the persistence of the condition is not related to an infection.
Gastroeneteritis is an acute infection of the lining of the stomach, small and large intestine often caused by a virus. The most profound effect is on the small intestine. It may be spread through the air, food or water. It differs from food poisoning, which also causes inflammation of the stomach and intestinal lining usually due to the action of bacteria and/or its toxins.
Signs and Symptoms
Viral gastroenteritis is a common infectious disease and the most common cause of sudden vomiting and diarrhea. Other prominent clinical features includes excessive nausea, abdominal pain and fever. This is discussed further under Gastroenteritis Symptoms.
Most cases of viral gastroenteritis last for less than a week. The most common stomach viruses responsible for gastroenteritis includes the various species of rotavirus and norovirus (Norwalk-like virus). Other viruses involved are discussed under Gastroenteritis Causes, along with the incubation periods and duration of infection. Viral gastroentritis is extremely contagious and easily spread among those in close quarters. Food and waterborne transmission is more common, although in infants and children, airborne transmission is prevalent and accounts for outbreaks in daycare facilities and schools.
Viral gastroenteritis is usually self-limiting and no specific treatment may be required. Preventing dehydration with proper oral rehydration therapy and introducing solid foods and a normal diet as soon as possible is the focus of management. In patients who are immunocompromised or if the infection is persisting, antiviral agents may have to be considered. Infants are considered a high risk group and require special attention.
Gastritis is the inflammation of the stomach lining usually accompanied by a disruption in the pH and volume of the stomach acid and/or protective mechanisms of the gastric mucosa. This may cause general inflammation (non-erosive) or areas where the lining is compromised (erosive). Gastritis may involve the entire stomach (pangastritis) or portions of the stomach. It is not uncommon for the terminal parts of the esophagus and proximal parts of the duodenum to also be affected.
Signs and Symptoms
The signs and symptoms of gastritis can vary and is often silent (asymptomatic). Nausea, gnawing pains in the stomach (gastric pain), bloating and other symptoms that are broadly defined as indigestion (dyspepsia) are usually present. Vomiting is rare but possible. These symptoms may be aggravated by certain trigger factors, like spicy foods, caffeinated drinks, medication like NSAIDs, and alcohol consumption.
Most cases of infectious gastritis are due to Helicobacter pylori infection. This is a bacterial infection although fungal and viral pathogens may also cause gastritis. Cytomegalovirus (CMV) infection is the more common cause of viral gastritis and is often associated with immunocopromised patients, like in HIV infection. Less frequently, the herpes virus may be responsible for viral gastritis. Gastritis is rarely contagious but may spread from person to person if there is very close contact and the same predisposing factors exist in both contacts.
The treatment depends on the type of gastritis. In terms of infectious gastritis, antimicrobials (antibiotics ~ bacteria, antivirals ~ viruses, antifungal ~ fungi) may be used along with antacids, proton pump inhibitors and H2-blockers, as well as other stomach acid medication, like prostaglandin analogues ad sucralfates. This is discussed in detail under Gastritis Treatment.