(NewsNation) — The Centers for Disease Control and Prevention (CDC) issued an alert last year warning of the spread of a strain of the shigella bacteria that appears to be resistant to antibiotics.

In 2022, approximately 5% of shigellosis infections were drug-resistant. There were zero reported instances of resistant infections in 2015, according to the CDC.

Now, Philadelphia health officials are closely monitoring a surge in infections, Axios reported.

What is Shigella?

Shigella is a bacterial infection causing symptoms like diarrhea, fever, and stomach pain. In rare cases, it can be fatal, according to the CDC.

How does it spread?

The infection spreads easily through person-to-person contact, especially among vulnerable groups such as the homeless or those with opioid-use disorder. Shigellosis usually affects young children aged 1-4 in the U.S., but the CDC has seen an increase in the following groups:

• Gay, bisexual and other men who have sex with men
• People experiencing homelessness
• Frequent International travelers
• People living with human immunodeficiency virus (HIV)

Shigella transmission occurs through ingesting contaminated food or water, during sexual activity, or through exposure to contaminated fecal matter, such as during diaper changes. Symptoms typically manifest within two days of exposure and can persist for weeks.

Is it deadly?

While typically not lethal, Shigella can lead to severe complications, particularly among individuals with weakened immune systems.

How is it treated?

Treatment involves antibiotics, though some strains of Shigella are becoming resistant to common medications, complicating management.

The outbreak, primarily affecting vulnerable populations, began showing significant increases in October, according to the Philadelphia Department of Public Health. Cases more than doubled compared to previous months, with a similar trend observed statewide.

State advisories also highlight uncertainties regarding the susceptibility of recent cases to antibiotic treatment.

How to prevent it?

While most people with diarrheal illness only needed “supportive care and fluid replacement,” the CDC said healthcare providers should consults with specialists to “determine the best treatment plan.”

To avoid contracting or spreading the bacteria, the CDC recommends washing your hands with soap and water, especially in the following circumstances:

• Before any sexual activity
• Before preparing food or eating
• After going to the bathroom, changing a diaper, or cleaning up after someone who went to the bathroom

The CDC also advised healthcare professionals to report all confirmed cases to their local health department.