**Question:** Traveller's diarrhea is caused due to: September 2009, 2010 & March 2013

**Core Concept:** Traveller's diarrhea is a common gastrointestinal disorder experienced by individuals traveling to developing countries, particularly in tropical regions. It is typically characterized by abrupt, watery diarrhea, abdominal cramps, and sometimes nausea or vomiting. The underlying cause is often due to bacterial infections, most commonly caused by the bacterium Escherichia coli (E. coli) and Campylobacter jejuni. These pathogens can be transmitted through contaminated food and water, poor hygiene, and close contact with infected individuals.

**Why the Correct Answer is Right:** Traveller's diarrhea is primarily caused by pathogenic bacteria, specifically E. coli and Campylobacter jejuni. These microorganisms can enter the gastrointestinal tract through ingestion of contaminated food or water, inadequate handwashing, and close contact with infected individuals. Once inside the body, they invade the intestinal lining, leading to inflammation and disruption of the intestinal barrier, causing diarrhea.

**Why Each Wrong Option is Incorrect:**

A. Infection by rotavirus or adenovirus: These viruses are responsible for viral gastroenteritis and are distinct from bacterial pathogens like E. coli and Campylobacter jejuni.

B. Ingestion of spicy food or local cuisine: While dietary factors can contribute to diarrhea in some cases, the primary cause is bacterial infection in traveller's diarrhea.

C. Lack of oral rehydration therapy: Oral rehydration therapy is a treatment for dehydration resulting from diarrhea, not the cause of the diarrhea itself.

D. Infection by Salmonella or Shigella: While these bacteria can cause enteric fever and dysentery, respectively, they are not the primary pathogens responsible for traveller's diarrhea. Traveller's diarrhea is more commonly caused by E. coli and Campylobacter jejuni.

**Clinical Pearl:** Proper precautions while traveling to endemic regions, such as consuming only boiled water, avoiding undercooked seafood, and maintaining personal hygiene, can significantly reduce the risk of acquiring traveller's diarrhea due to E. coli and Campylobacter jejuni. Antibiotics are often prescribed for treating the infection, but their misuse can lead to antibiotic-resistant bacteria, exacerbating the problem.