Shigellosis is an acute infectious disease caused by a group of bacteria called Shigella. This infection targets the digestive tract, causing inflammation and painful symptoms in the lining of the intestines. Transmission primarily occurs through the fecal-oral route, often by consuming contaminated food or water, or through direct person-to-person contact due to poor hygiene. The resulting illness, characterized by diarrhea, fever, and abdominal cramps, is highly contagious.
The Typical Length of Acute Illness
The acute symptoms of shigellosis usually begin within one to four days following exposure to the bacteria. The infection often starts with watery diarrhea, which can progress to include blood and mucus, a condition known as dysentery. Accompanying symptoms frequently include fever, stomach pain, and a constant, painful urge to pass stool.
For most healthy individuals, shigellosis is a self-limited infection, meaning it typically resolves without specific medical treatment. The full duration of the acute illness, from the onset of symptoms to their resolution, generally lasts for about five to seven days. While most people recover within this timeframe, symptoms may persist for longer than one week in some cases.
Duration of Contagiousness (Shedding)
The period of contagiousness, or “shedding,” is the time the bacteria are present in the stool and capable of transmission. Individuals remain infectious for as long as they are shedding the Shigella bacteria, which can be much longer than the duration of acute symptoms. The shedding period can extend for up to four weeks after the initial onset of the illness, even after diarrhea has resolved.
In some cases, especially in asymptomatic individuals or those who have not received treatment, the bacteria can be shed for several months. Strict adherence to hygiene protocols, particularly handwashing, is important for preventing onward transmission during this extended period. Antibiotic treatment, when medically appropriate, is often recommended to shorten the illness and significantly reduce the shedding period. This reduction is particularly important for individuals in high-risk occupations, such as food handlers and healthcare workers.
Variables That Affect Recovery Time
Several factors can influence the overall timeline of shigellosis, either shortening or prolonging recovery. The specific species of Shigella involved plays a role in the severity and duration of the illness. For example, Shigella sonnei infections are often milder than those caused by Shigella dysenteriae, which is associated with more severe disease.
A person’s age and underlying health status also significantly impact recovery time. Young children, the elderly, and individuals with compromised immune systems tend to experience more prolonged and severe infections. If initiated promptly, antibiotic therapy can shorten the duration of symptoms by approximately two days. However, the increasing prevalence of antibiotic-resistant Shigella strains can complicate treatment and potentially extend the illness period.
Signs That Require Urgent Medical Care
Although shigellosis is often self-limiting, certain signs indicate the need for urgent medical evaluation due to potential complications. Signs of severe dehydration are a major concern, including lethargy, dizziness, excessive thirst, and a significant decrease in urination. Persistent, high fever above 102°F, especially in children, should prompt immediate attention.
Other red flags include bloody diarrhea lasting more than three days, or the development of neurological symptoms such as seizures or altered mental status. In rare cases, shigellosis can lead to Hemolytic Uremic Syndrome (HUS), a severe complication that affects the blood and kidneys. HUS drastically changes the expected recovery timeline and requires immediate, specialized medical care.