2025 – PAGE 329 – INFECTIOUS DISEASES

ROTAVIRUS

Look for rotavirus in younger children up to 3 or 4 years of age. It usually presents with a WATERY diarrhea with no flecks of blood. It CAN be associated with a fever and vomiting. Diagnose with antigen testing of the stool and treat supportively.

PEARL: Rotavirus is NOT associated with food and water intake. Do not pick this for a child who has recently been on a camping trip or a picnic.

ADENOVIRUS

Look for fever, vomiting, and diarrhea a few days after a picnic to indicate adenovirus. Adenovirus IS associated with food. It is usually short-lived and resolves within a week. Treatment is supportive.

NOROVIRUS

Look for acute onset of profuse, watery diarrhea, nausea, vomiting, abdominal cramps, and potential fever. It is highly contagious and spread through direct contact, contaminated food and water. Diagnose via stool RT-PCR. Treatment is supportive. Isolation helps to contain outbreaks. It is the most common cause of viral gastroenteritis in areas where rotavirus vaccination is routine.

NORWALK VIRUS

Look for Norwalk virus in an older child with diarrhea who recently ate raw SEAFOOD.

MNEMONIC: Can you really imagine a child younger than 5 or 6 using chopsticks to eat sushi? I can’t. Imagine taking a stroll along a “NORWALK” (instead of “boardwalk”) next to the ocean. This should help you remember that NORWALK is associated with SEAfood.

ESCHERICHIA COLI (E. coli)

Escherichia coli (E. coli) is a gram-negative bacteria that can cause multiple types of diarrhea.

• ENTEROHEMORRHAGIC E. COLI (EHEC): As the word “hemorrhagic” suggests, look for BLOODY diarrhea caused by a Shiga toxin-producing E. coli, such as O157:H7 or O103:H4. These are also known as Shiga toxin-producing Escherichia coli (STEC). The STEC variety of E. coli is known to also cause Hemolytic Uremic Syndrome (HUS), so also look for evidence of renal dysfunction.
  • PEARL: Do NOT give antibiotics because that makes this worse!
• ENTEROTOXIGENIC E. COLI (ETEC): This is your classic “traveler’s diarrhea.” Look for a non-bloody diarrhea associated with crampy abdominal pain. This can be associated with fever and vomiting. Look for it in someone who recently went on a vacation. It’s self-limited. Use a macrolide (azithromycin is preferred) if the diarrhea is persisting for greater than a week. Resistance to trimethoprim-sulfamethoxazole and doxycycline is too high for them to be used as first-line drugs. Do NOT use quinolones for kids. Loperamide is okay! The CDC does not recommend antibiotic prophylaxis.
• ENTEROPATHOGENIC E. COLI (EPEC): Key phrase = POOR SANITATION. It’s a non-bloody, acute or chronic diarrhea. It’s probably low-yield for the pediatric boards.
• ENTEROINVASIVE E. COLI (EIEC): VERY similar in presentation to Shigella. Look for a BLOODY diarrhea associated with mucous and TENESMUS.

SHIGELLA INFECTIONS

Shigella species are gram-negative organisms that can cause illness ranging from self-limited episodes of bloody or non-bloody diarrhea up to SEVERE symptoms including high fever, bloody diarrhea, and TENESMUS. Shigella dysenteriae tends to cause more serious disease but is rare in the U.S. Some of the more serious complications of Shigella infections include rectal prolapse and seizures. These patients will LOOK SICK, and WBC may show a high neutrophil count and a BANDEMIA. Blood and WBC in the stool are suggestive. Diagnose with stool culture. There is controversy over whether to treat mildly ill patients. Usually mildly ill patients are only given symptomatic care. Treat sicker patients with antibiotics. Choose the antibiotic based on the degree of illness severity, immunocompromised state, local antibiotic resistance patterns, and history of travel to endemic areas. Ciprofloxacin or ceftriaxone are first-line agents. Quinolones in older teens may be okay (subject to the usual precautions). Oral azithromycin is the treatment of choice for less ill children when sensitivities are not known.

PEARL: Oral amoxicilin is ineffective in treating Shigella, so don’t pick this answer on the boards.

PEARL: Tenesmus is the feeling of incomplete stool evacuation. It can be associated with pain, straining, or cramping. It can also be seen in Entamoeba histolytica.

MNEMONIC: Sing the following, “Shigella makes you SHAKE A LEG y’all!” Now imagine that Shigella is making you SHAKE A LEG as you are having a SEIZURE. You shake your leg so hard that your RECTUM prolapses, and along with it a TENNIS BALL comes out!

• KEY: SHAKE A LEG = Seizure, and the TENNIS BALL represents TENESMUS.