The FNP Review

The 4 Infectious Disease Scenarios Every FNP Student Must Master Before Boards

Infectious Disease · 3 min read · August 10, 2026

Introduction

Infectious disease questions make up a substantial portion of both the AANP and ANCC family nurse practitioner certification exams. The secret to mastering this domain is recognizing the subtle patterns that differentiate common pathologies. Rather than trying to memorize every textbook bug and drug, focus your energy on the classic clinical presentations and first-line treatments that board writers love to test.

1. Lyme Disease: Spotting the Bullseye and Knowing Your Stages

Lyme disease, caused by the spirochete Borrelia burgdorferi and transmitted by the blacklegged tick, is a perennial favorite on board exams. The hallmark of early localized infection is erythema migrans—the classic "bullseye" rash that appears 7 to 14 days after a tick bite. However, keep in mind that not all patients develop the classic bullseye; many simply present with a uniformly expanding erythematous patch.

  • Early Localized: Treat with oral doxycycline 100 mg twice daily for 14 to 21 days.
  • Alternative Option: For pregnant women or children under 8 years old where doxycycline is traditionally avoided, use amoxicillin.
  • Disseminated/Late Disease: May manifest as neurologic symptoms (facial nerve palsy) or cardiac involvement (AV heart block).

Board Tip: Doxycycline is now considered safe for children of all ages when used for short courses (less than 21 days) for suspected tick-borne rickettsial diseases like Lyme, according to the CDC and AAP guidelines. Expect the boards to test this updated safety profile.

2. Strep Throat and Preventing Rheumatic Fever

Pharyngitis is a daily bread-and-butter complaint in primary care, but board exams specifically test your ability to differentiate viral pharyngitis from group A beta-hemolytic streptococcus (GABHS). Use the Centor Criteria to guide your clinical decision-making: fever, tender anterior cervical adenopathy, lack of a cough, and pharyngotonsillar exudates.

  • First-Line Treatment: Penicillin V potassium or intramuscular benzathine penicillin G.
  • Penicillin Allergy: Use erythromycin or azithromycin (macrolides), though local resistance patterns should be kept in mind.

Clinical Pearl: The primary goal of treating GABHS is not just symptom relief, but the prevention of acute rheumatic fever. Interestingly, treating strep throat does not prevent acute post-streptococcal glomerulonephritis (APSGN).

3. Atypical Pneumonia vs. Community-Acquired Pneumonia

When evaluating a patient with a cough and infiltrates on a chest X-ray, you must distinguish between typical bacterial pathogens (like Streptococcus pneumoniae) and atypical pathogens (like Mycoplasma pneumoniae).

  • Atypical Pneumonia ("Walking Pneumonia"): Frequently seen in younger adults and school-aged children. Symptoms are insidious and often include a persistent, dry hacking cough, low-grade fever, and malaise. Chest X-ray findings often look much worse than the patient feels.
  • Treatment: Macrolides (azithromycin) or doxycycline.
  • Typical Pneumonia: Often presents acutely with high fever, shaking chills, productive cough with rust-colored sputum, and lobar consolidation on imaging.
  • Treatment: Respiratory fluoroquinolones (levofloxacin) or high-dose amoxicillin.

Board Tip: If a board question describes a college student or military recruit with a hacking cough, headache, and a diffuse rash or bullous myringitis, think Mycoplasma pneumoniae and reach for a macrolide.

4. Uncomplicated Urinary Tract Infections in Special Populations

UTIs are ubiquitous in primary care, but the boards love to test exceptions to the standard treatment rules. Uncomplicated lower UTIs in non-pregnant adult females are typically caused by Escherichia coli.

  • First-Line Treatment: Nitrofurantoin (Macrobid) 100 mg BID for 5 days (avoid if suspecting pyelonephritis or if CrCl is under 30 mL/min) or Trimethoprim-sulfamethoxazole (Bactrim DS) BID for 3 days (if local resistance is under 20%).
  • Pregnant Women: Always screen and treat asymptomatic bacteriuria. Safe options include amoxicillin, cephalexin, or nitrofurantoin (avoid in the first trimester and near term due to risk of kernicterus).

Conclusion and Next Steps

You have what it takes to conquer the infectious disease section on your upcoming boards. By focusing on hallmark physical exam findings, precise first-line therapies, and high-yield board exceptions, you will walk into your exam room with calm, collected confidence.

Take a deep breath—you are fully capable of crushing this exam. Head over to The FNP Review for more targeted board prep resources designed to help you study smarter, not harder.