Shigella causes diarrhea, sometimes bloody, that can last for 5 to 7 days. It is highly infectious and is spread from a person who is sick to another person via the fecal oral route. So hand washing is important. It is considered a foodborne pathogen, so food that has been handled by someone with Shigella can serve as a vector.
Keys to prevention - Exclusion of people who have the symptoms or who have been diagnosed, and proper hand washing.
US News and World Report
Drug-Resistant Stomach Bug Spreading Across the U.S.
By Kimberly Leonard April 2, 2015 | 5:26 p.m. EDT
Travelers are infecting Americans when they return home.
A recent, rapid spread of a diarrhea-causing bug that is immune to medicine has caused government health officials to issue a warning to travelers about their hygiene.
Once again highlighting the issue of drug resistant infections in the U.S., the warning from the Centers for Disease Control and Prevention came less than a week after the White House announced an aggressive initiative to contain the spread of drug-resistant bacteria, which causes 2 million illnesses and 23,000 deaths in the U.S. each year.
The topic of antibiotic-resistant bacteria jumped to the forefront of national conversation after a recent spread of a "superbug" by a medical device used in hospitals caused several deaths and many illnesses.
The current spread of the bacteria, Shigella, has resulted in 243 cases in 32 states and Puerto Rico. Approximately half come from international travel. Patients range in age from 20 years to 50 years old and men and women have been affected about equally.
Dr. Anna Bowen, a CDC medical epidemiologist and lead author of the study about the outbreak, recommends against using the word "superbug" for this bacteria. "It would be better to say resistant to the first-time treatment choice," she says.
Illustration of the Shigella bacteria.
Although diarrhea caused by the bacteria goes away without treatment, people with mild illnesses are often treated with antibiotics to stop the diarrhea faster. Now, the antibiotic – ciprofloxacin, or "Cipro" – isn't working when patients take it. The disease can be particularly difficult for people who have poor immune systems or other underlying illnesses. During this outbreak 22 percent of patients were hospitalized.
"I'm no longer surprised when I see these," says Dr. Pritish Tosh, an infectious disease physician and vaccine researcher at the Mayo Clinic in Rochester, Minnesota. "The finding that several bacteria are resistant to what would commonly have been used is indicative of the growing trend of antibiotic resistance."
The resistance occurs when someone has repeated exposure to antibiotics. A bacteria then mutates or takes on new genes, making an antibiotic unable to kill it or inhibit its growth. Antibiotics are administered to about half of hospital patients, according to the Association for Professionals in Infection Control and Epidemiology. The medicines are often used to protect those undergoing surgery, who become vulnerable to bacterial infections after procedures ranging from hip replacements to organ transplants. Studies by the CDC have shown, however, that 30 percent to 50 percent of antibiotics prescribed in hospitals are unnecessary or incorrect.
The drug resistance that has been seen in recent months throughout the country is predominantly caused by the overuse of antibiotics, Tosh says.
Giving someone a prescription for an antibiotic might seem like a low-risk thing to do, he points out. "It can be hard to think about or weigh the big, long-term societal risks," he says.
Shigella isn't uncommon to the U.S. It causes an estimated 500,000 cases each year, according to the CDC, and is transmitted easily from person to person and through contaminated food and recreational water. It is not spread through animals, but rather through people who handle food. "When handwashing isn’t practiced perfectly, germs can be transferred from one person’s hands to the next, into that person’s food, or into the food that person prepares for others," Bowen says.
Once transmitted, it can cause watery or bloody diarrhea, abdominal pain, fever and malaise.
Officials already know that most of this type of bacteria is resistant to two other drugs – ampicillin and trimethoprim/sulfamethoxazole – but this aggressive outbreak is new. Until recently, the resistance to Cipro has occurred in just 2 percent of infections tested in the U.S., but was found in 90 percent of samples tested in recent clusters.
“These outbreaks show a troubling trend in Shigella infections in the United States,” Dr. Tom Frieden, director of the CDC, said in a statement. “Drug-resistant infections are harder to treat and because Shigella spreads so easily between people, the potential for more – and larger – outbreaks is a real concern. We’re moving quickly to implement a national strategy to curb antibiotic resistance because we can’t take for granted that we’ll always have the drugs we need to fight common infections.”
The CDC began detecting the bacteria in December 2014, finding that travelers came to the U.S. and spread the bacteria to those who had not traveled. Travelers came from destinations such as Hispaniola, India, Morocco and destinations in Asia and Europe. The CDC did not find any common airline or airport exposures. Most travelers to the Dominican Republic stayed at resorts in Punta Cana, but no common hotel, resort, restaurant or event was reported.
"Travelers need to be aware of the risks of acquiring multidrug-resistant pathogens, carefully wash their hands, and adhere to food and water precautions during international travel," authors wrote in the CDC's Morbidity and Mortality Weekly Report.
The biggest outbreak – of 45 cases – was reported in Massachusetts. California had 25 cases and there were 18 cases in Pennsylvania.
It is possible for the bacteria to spread in health care facilities if there are lapses in hygiene, Bowen says, but most transmissions are in settings where hygiene practices or infrastructure are less well established, like in childcare centers, or in the case of this outbreak, among the homeless.
In San Francisco, the Department of Public Health identified an outbreak of 95 cases of the bacteria, nine of which were tested and are included in the final count. Half of cases occurred in the homeless population there, among those living in single-room occupancy hotels, according to the CDC report.
"It certainly is concerning," Tosh says. "A lot needs to be done to reduce the antibiotic use and to improve our diagnostics."
Shigellosis is a diarrheal disease caused by a group of bacteria called Shigella. Shigella causes about 500,000 cases of diarrhea in the United States annually 1. There are four different species of Shigella:
Shigella sonnei (the most common species in the United States)
Symptoms of shigellosis typically start 1–2 days after exposure and include:
- Diarrhea (sometimes bloody)
- Abdominal pain
- Tenesmus (a painful sensation of needing to pass stools even when bowels are empty)
In persons with healthy immune systems, symptoms usually last about 5 to 7 days. Persons with diarrhea usually recover completely, although it may be several months before their bowel habits are entirely normal. Once someone has had shigellosis, they are not likely to get infected with that specific type again for at least several years. However, they can still get infected with other types of Shigella.
Possible complications from Shigella infections include:
Post-infectious arthritis. About 2% of persons who are infected with Shigella flexneri later develop pains in their joints, irritation of the eyes, and painful urination. This is called post-infectious arthritis. It can last for months or years, and can lead to chronic arthritis. Post-infectious arthritis is caused by a reaction to Shigella infection that happens only in people who are genetically predisposed to it 2.
Blood stream infections. Although rare, blood stream infections are caused either by Shigella organisms or by other germs in the gut that get into the bloodstream when the lining of the intestines is damaged during shigellosis. Blood stream infections are most common among patients with weakened immune systems, such as those with HIV, cancer, or severe malnutrition 2.
Seizures. Generalized seizures have been reported occasionally among young children with shigellosis, and usually resolve without treatment. Children who experience seizures while infected with Shigella typically have a high fever or abnormal blood electrolytes (salts), but it is not well understood why the seizures occur 2.
Hemolytic-uremic syndrome or HUS. HUS occurs when bacteria enter the digestive system and produce a toxin that destroys red blood cells. Patients with HUS often have bloody diarrhea. HUS is only associated with Shiga-toxin producing Shigella, which is found most commonly in Shigella dysenteriae 2.
Shigella germs are present in the stools of infected persons while they have diarrhea and for up to a week or two after the diarrhea has gone away. Shigella is very contagious; exposure to even a tiny amount of contaminated fecal matter—too small to see-- can cause infection. Transmission of Shigella occurs when people put something in their mouths or swallow something that has come into contact with stool of a person infected with Shigella. This can happen when:
- Contaminated hands touch your food or mouth. Hands can become contaminated through a variety of activities, such as touching surfaces (e.g., toys, bathroom fixtures, changing tables, diaper pails) that have been contaminated by stool from an infected person. Hands can also become contaminated with Shigella while changing the diaper of an infected child or caring for an infected person.
- Eating food contaminated with Shigella. Food may become contaminated if food handlers have shigellosis. Produce can become contaminated if growing fields contain human sewage. Flies can breed in infected feces and then contaminate food when they land on it.
- Swallowing recreational (for example lake or river water while swimming) or drinking water that was contaminated by infected fecal matter.
- Exposure to feces through sexual contact.
Currently, there is no vaccine to prevent shigellosis. However, you can reduce your risk of getting shigellosis by:
Carefully washing your hands with soap during key times:
- Before eating.
- After changing a diaper or helping to clean another person who has defecated (pooped).
- If you care for a child in diapers who has shigellosis, promptly discard the soiled diapers in a lidded, lined garbage can, and wash your hands and the child’s hands carefully with soap and water immediately after changing the diapers. Any leaks or spills of diaper contents should be cleaned up immediately.
- Avoid swallowing water from ponds, lakes, or untreated swimming pools.
- When traveling internationally, follow food and water precautions strictly and wash hands with soap frequently. For more information, see Travelers' Health - Food and Water Safety.
- Avoid sexual activity with those who have diarrhea or who recently recovered from diarrhea.
Diarrhea caused by Shigella usually resolves without antibiotic treatment in 5 to 7 days. People with mild shigellosis may need only fluids and rest. Bismuth subsalicylate (e.g., Pepto-Bismol®) may be helpful 3, 4, but medications that cause the gut to slow down, such as loperamide (e.g., Imodium®) or diphenoxylate with atropine (e.g., Lomotil®), should be avoided 5. Antibiotics are useful for severe cases of shigellosis because they can reduce the duration of symptoms 6.
In 2013, CDC declared antibiotic-resistant Shigella an urgent threat in the United States 7. Resistance to traditional first-line antibiotics like ampicillin and trimethoprim-sulfamethoxazole is common among Shigella globally, and resistance to some other important antibiotics is increasing 8-13. While travelers to the developing world are at particular risk of acquiring antibiotic-resistant shigellosis, outbreaks of shigellosis resistant to ciprofloxacin or azithromycin—the two antibiotics most commonly used to treat shigellosis—have been reported recently within the United States and other industrialized countries 14-18. About 27,000 Shigella infections in the United States every year are resistant to one or both of these antibiotics 7. When pathogens are resistant to common antibiotic medications, patients may need to be treated with medications that may be less effective, but more toxic and expensive. To learn more about antibiotic resistance, see Antibiotic / Antimicrobial Resistance