VIRULENT BACTERIUM SHIGELLA

PRERNA FOR IAS

VIRULENT BACTERIUM SHIGELLA

1. What is Shigella?

Shigella is a Gram-negative, rod-shaped, highly contagious bacterium that causes shigellosis, an infectious disease affecting the intestines. It was first identified in 1897 by Japanese bacteriologist Kiyoshi Shiga, after whom it is named. The bacterium invades the lining of the large intestine, causing inflammation and severe diarrhoea. Only a very small number of bacteria are needed to cause infection, making it highly infectious. Shigella is a major public health concern in developing countries where sanitation is poor. Early diagnosis, proper hygiene, and timely treatment are essential to prevent outbreaks and reduce disease transmission.

2. Symptoms

The symptoms of shigellosis usually appear one to three days after infection. Common symptoms include fever, abdominal pain, stomach cramps, watery or bloody diarrhoea (dysentery), nausea, and vomiting. Frequent bowel movements may lead to dehydration, weakness, and fatigue. In severe cases, complications such as seizures, kidney damage, or bloodstream infections may occur, especially in children and elderly individuals. Some infected people may experience only mild symptoms, while others become seriously ill. If diarrhoea is persistent, bloody, or accompanied by high fever and dehydration, immediate medical attention is necessary to prevent life-threatening complications.

3. How Does It Spread?

Shigella spreads mainly through the faecal-oral route, where bacteria from infected stool enter another person's mouth. Infection commonly occurs by consuming contaminated food or water, touching contaminated surfaces, or through poor hand hygiene after using the toilet. Even 10–100 bacteria can cause infection, making transmission extremely easy. Flies may also spread the bacteria by contaminating food. Crowded living conditions, poor sanitation, unsafe drinking water, and improper food handling increase the risk of outbreaks. Washing hands with soap, drinking clean water, and maintaining proper sanitation are the most effective ways to prevent the spread of shigellosis.

4. Global Burden

Shigellosis is a major global health problem, particularly in low- and middle-income countries. It causes an estimated 80–165 million infections and around 600,000 deaths each year, mainly among children under five years of age. The disease is especially common in regions with poor sanitation, including South Asia and sub-Saharan Africa. Frequent outbreaks occur in schools, refugee camps, and densely populated communities where access to clean water is limited. The disease places a significant burden on healthcare systems and economies. Improving sanitation, safe water supply, vaccination research, and public health awareness can greatly reduce its impact.

5. Who is Most at Risk?

Certain groups are more vulnerable to Shigella infection. Children under five years of age experience the highest number of infections because of developing immune systems and poor hygiene practices. Elderly individuals, especially those above 40 years, may also face increased risk of severe illness. People with weakened immune systems, including those with HIV/AIDS, cancer, or chronic illnesses, are more likely to develop complications. Travellers visiting areas with poor sanitation are also at risk. Humans are the primary reservoir of the bacteria, and transmission often occurs in families, schools, childcare centres, hospitals, and crowded community settings.

6. Kerala Outbreak 2026

The Kerala Shigella outbreak of 2026 highlighted the importance of sanitation and public health surveillance. The outbreak was first detected in March 2026, affecting several districts, including Kozhikode, Wayanad, Malappuram, and Kannur. Many infected individuals were schoolchildren, and several required hospitalization. Health authorities traced the outbreak mainly to contaminated water sources, unsafe food, and poor hygiene practices in community settings. Rapid response measures included medical treatment, water quality monitoring, sanitation improvements, and public awareness campaigns. The incident emphasized the need for clean drinking water, proper sanitation, and early detection to prevent future outbreaks.

7. Earlier Kerala Incidents

Kerala has experienced several Shigella outbreaks over the years, demonstrating the recurring threat posed by this bacterium. In 2009, more than 300 people reportedly suffered from food-borne shigellosis across the state. In 2020, an outbreak in Kozhikode resulted in multiple infections and one child's death. Another food-poisoning incident in Kasaragod in 2022 hospitalized many people and caused one fatality. These repeated outbreaks were linked to contaminated food, unsafe drinking water, and poor hygiene. They underline the importance of regular disease surveillance, improved sanitation, safe food handling, and public health education to reduce infection risks.

8. Treatment and Control

Most mild cases of shigellosis recover with adequate hydration, rest, and oral rehydration solutions (ORS) to prevent dehydration. Severe infections may require antibiotics, but laboratory testing is important because some strains are resistant to commonly used medicines. Doctors prescribe antibiotics only when necessary to avoid increasing antibiotic resistance. Maintaining good personal hygiene, washing hands with soap, consuming safe drinking water, and following proper food safety practices are essential preventive measures. During outbreaks, early diagnosis, isolation of infected individuals, sanitation improvements, and health education help limit disease spread and protect vulnerable populations from serious complications.

9. Emerging Concern

A major concern today is the rise of multidrug-resistant (MDR) Shigella, which no longer responds to several commonly used antibiotics. This makes treatment more difficult and increases the risk of prolonged illness, hospitalisation, and death. Continuous disease surveillance, laboratory testing, and monitoring of antibiotic resistance patterns are essential for selecting effective treatments. Health authorities encourage the rational use of antibiotics to slow the development of resistance. Research on vaccines and new antimicrobial drugs is ongoing. Strengthening sanitation systems, improving hygiene practices, and promoting responsible antibiotic use remain the most effective long-term strategies for controlling Shigella infections worldwide.

10. Key Takeaway

Shigella is a highly infectious bacterium that causes shigellosis, a serious diarrhoeal disease spread mainly through contaminated food, water, and poor hygiene. Young children, elderly individuals, and people with weakened immunity are the most vulnerable. Early diagnosis, proper hydration, laboratory-guided antibiotic treatment, and strict hygiene practices are crucial for controlling the disease. Recent outbreaks, including those reported in Kerala, highlight the need for improved sanitation, clean drinking water, public health awareness, and disease surveillance. With the growing challenge of antibiotic-resistant strains, prevention through hygiene and responsible antibiotic use remains the most effective strategy for protecting public health.