are widely available; alternatively, purified water or other clear liquids are recommended, along with salty crackers or oral rehydration salts (available in stores and pharmacies in most countries) to replenish lost electrolytes. carbonated water or soda, left open to allow dissipation of the carbonation, is useful when nothing else is available. in severe or protracted cases, the oversight of a medical professional is advised. antibiotics if diarrhea becomes severe (typically defined as three or more loose stools in an eight-hour period), especially if associated with nausea, vomiting, abdominal cramps, fever, or blood in stools, medical treatment should be sought. such patients may benefit from antimicrobial therapy. a 2000 literature review found that antibiotic treatment shortens the duration and severity of td; most reported side effects were minor, or resolved on stopping the antibiotic. the antibiotic recommended varies based upon the destination of travel. trimethoprim–sulfamethoxazole and doxycycline are no longer recommended because of high levels of resistance to these agents. antibiotics are typically given for three to five days, but single doses of azithromycin or levofloxacin have been used. rifaximin and rifamycin are approved in the u.s. for treatment of td caused by etec. if diarrhea persists despite therapy, travelers should be evaluated for bacterial strains resistant to the prescribed antibiotic, possible viral or parasitic infections, bacterial or amoebic dysentery, giardia, helminths, or cholera. antimotility agents antimotility drugs such as loperamide and diphenoxylate reduce the symptoms of diarrhea by slowing transit time in the gut. they may be taken to slow the frequency of stools, but not enough to stop bowel movements completely, which delays expulsion of the causative organisms from the intestines. they should be avoided in patients with fever, bloody diarrhea, and possible inflammatory diarrhea. adverse reactions may include nausea, vomiting, abdominal pain, hives or rash, and loss of appetite. antimotility agents should not, as a rule, be taken by children under age two. epidemiology an estimated 10 million people—20 to 50% of international travelers—develop td each year. it is more common in the developing world, where rates exceed 60%, but has been reported in some form in virtually every travel destination in the world. society and culture moctezuma's revenge is a colloquial term for travelers' diarrhea contracted in mexico. the name refers to moctezuma ii (1466–1520), the tlatoani (ruler) of the aztec civilization who was overthrown by the spanish conquistador hernán cortés in the early 16th century, thereby bringing large portions of what is now mexico and central america under the rule of the spanish crown. wilderness diarrhea main article: wilderness acquired diarrhea wilderness diarrhea, also called wilderness-acquired diarrhea (wad) or backcountry diarrhea, refers to diarrhea among backpackers, hikers, campers and other outdoor recreationalists in wilderness or backcountry situations, either at home or abroad. it is caused by the same fecal microorganisms as other forms of travelers' diarrhea, usually bacterial or viral. since wilderness campsites seldom provide access to sanitation facilities, the infection risk is similar to that of any developing country. water treatment, good hygiene, and dish washing have all been shown to reduce the incidence of wad.