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The National Academies: What You Need To Know About Infectious Disease

What You Need To Know About Infectious Disease


Dysentery is the inflammation of the colon characterized by frequent, watery stools, often tinged with blood and mucus. Dysentery is usually caused by one of two different organisms—Shigella bacteria or an amoeba, Entamoeba histolytica. Bacillary dysentery is more common in the developed world, while amoebic dysentery more frequently occurs in tropical areas with poor sanitary conditions. Inadequate hygiene is the most common cause of dysentery, but it can also be spread by tainted food, contaminated water, and exposure to human feces, for example, by changing diapers.

Symptoms of bacillary dysentery, a milder form of the disease, usually appear between 1 and 3 days after an individual is infected. Bacillary dysentery typically begins with a stomachache, followed by diarrhea and fever. Children younger than 2 years old may develop severe infections and should be monitored carefully.

Amoebic dysentery is more serious and presents with a wider range of symptoms that develop at least 2 to 4 weeks after exposure. Symptoms include fever, chills, nausea, and vomiting; watery diarrhea with mucus and blood; painful bowel movements; fatigue; and intermittent constipation. If untreated, the amoeba can break through the intestinal wall, spread into the bloodstream, and infect other organs, although this is very rare.

Because vomiting and diarrhea can lead to dehydration, individuals with dysentery must drink plenty of fluids. If an analysis of a stool sample shows that bacteria are the cause, medication may not be prescribed unless symptoms are severe. In mild cases, symptoms typically dissipate on their own within a week. For amoebic dysentery, patients will likely be given a 10-day course of one or more antimicrobial medications. 

Hygiene practices are the best defense against dysentery. Washing hands after using the bathroom and before preparing food is essential. If traveling to the tropics—where dysentery is common—drink bottled water, even when brushing your teeth, and avoid ice cubes, especially if you do not know what water was used to make them. Only eat food that has been cooked thoroughly.


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What do you know about infectious disease?

Which are larger?

  • Correct!

    Bacteria are 10 to 100 times larger than viruses.

  • Sorry, that’s incorrect.

    Bacteria are 10 to 100 times larger than viruses.

Infectious Disease Defined


Inflammation of the brain, often caused by a virus.

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