Family Medicine: Infectious Disease

Pertussis

Highly contagious respiratory illness caused by Bordetella pertussis, which has adolescents and adults as the primary reservoir but highest mortality in infants < 6 months

-Presentation: rhinorrhea/mild cough/low fever (Catarrhal stage, 1-2 weeks), paroxysms of coughing/whoop on inspiration/post-tussive vomiting (Paroxysmal stage, 2-6 weeks), and gradual improvement (Convalescent stage, weeks to months)

-Dx: nasopharyngeal swab PCR, lymphocytosis on CBC

-Tx: azithromycin, post-exposure prophylaxis for all close contacts, and prevention with TDAP/DTAP

Catarrhal

What stage of pertussis presentation is being described?

-Resembles a viral URI with rhinorrhea, mild cough, low grade fever

-Most contagious stage

-Lasts 1-2 weeks

Paroxysmal

What stage of pertussis presentation is being described?

-Paroxysms of cough, inspiratory whoop, post-tussive vomiting. Often afebrile, cyanosis in infants

-2 to 6 weeks

Convalescent

What stage of pertussis presentation is being described?

-Gradual improvement, cough diminishes

-Takes weeks to months

PCR

What is the gold standard diagnosis for pertussis?

Azithromycin

What is the treatment of choice for pertussis?

Post exposure prophylaxis

If someone tests positive for pertussis, what is required for all close contacts regardless of vaccination status?

28 weeks

When should the TDAP booster be given during pregnancy?

Fever Without a Source (FWS)

Acute febrile illness in a child under 36 months in whom the history and physical exam fail to reveal a cause

-Workup is age stratified because of the risk of serious bacterial infection

Rectal temp > 100.4

Fever is defined as what in infants?

0-28 days

What age of children require this workup for fever?

-Full sepsis workup, regardless of appearance → CBC, blood cultures, UA, urine culture, LP

Admit + IV ampicillin and gentamicin

What is the treatment of choice for fever in a neonate (0-28 days)?

29-60 days

What age of children require this workup for fever?

-Apply Rochester, Philadelphia, or Boston criteria for risk stratification, which is based on WBC count, absolute neutrophil count, UA, and inflammatory markers

-Low-risk, well-appearing infants may be observed with close follow-up. High risk require full septic workup

61-90 days

What age of children require this workup for fever?

-UA + urine culture is highest yield

UA

What should be obtained in the following febrile patients?

-Girls < 24 months, uncircumcised boys < 12 months, circumcised boys < 6 months, or any child with a fever > 39 C and no obvious source

Febrile Seizure

Brief generalized seizure with fever in a 6 month - 5 year old child with a normal neuro exam

Kawasaki Disease

Fever > 5 days + conjunctivitis, rash, and extremity changes

Histoplasmosis

Mention of Ohio and Mississippi River valleys or bird/bat droppings should make you think of what fungal infection?

Coccidiomycosis

Mention of the Southwest U.S. (Arizona, California) in a patient with fever, cough, erythema nodosum, and arthralgias should make you think of what fungal infection?

Blastomycosis

Mention of the Midwest, Mississippi/Ohio valleys, Great Lakes in a patient with pulmonary, skin, and bone lesions should make you think of what fungal infection?

Sporotrichosis

Mention of rose gardening or sphagnum moss in a patient with nodular lymphangitic spread up the arm should make you think of what fungal infection?

Itraconazole

What is the treatment of choice for Sporotrichosis?

Candidiasis

Fungal infection that can be mucocutaneous (thrush or vaginal), hematogenous, or related to HIV

-Treat with fluconazole or nystatin swish and swallow

Cryptococcosis

Opportunistic fungal infection due to Cryptococcus neoformans, considered an AIDs defining illness (CD4 < 100)

-Presentation: meningitis with India ink-positive encapsulated yeast

-Tx: amphotericin B + flucytosine + fluconazole

Aspergillosis

Opportunistic fungal infection that can be allergic (asthma/CF), aspergilloma (fungus ball in old TB cavity), or invasive (neutropenic or transplant patient)

-Tx: voriconazole

Pneumocystis pneumonia

Opportunistic fungal infection due to Pneumocystis jirovecii, considered an AIDS defining illness with CD4 < 200.

-Presentation: dry cough, dyspnea, bilateral interstitial infiltrates, elevated LDH

-Tx: bactrim

Bactrim

What should be used for primary prophylaxis in a patient with HIV who is CD4 < 200?

Giardiasis

Intestinal protozoa, Giardia lamblia, that is acquired from contaminated water (camping, daycare)

-Presentation: foul-smelling, greasy, non-bloody diarrhea + steatorrhea

-Dx: stool O&P or antigen test

-Tx: metronidazole

Metronidazole

What is the treatment of choice for Giardiasis?

Cryptosporidiosis

Intestinal protozoa, Cryptosporidium parvum, that causes watery diarrhea

-Severe and prolonged in HIV/AIDS (CD4 < 100)

-Dx: Modified acid-fast stain

-Tx: Nitazoxanide if immunocompetent, antiretroviral therapy for HIV

Amebiasis

Intestinal protozoa, Entamoeba histolytica, that is seen most often in travelers and immigrants

-Presentation: bloody diarrhea + RUQ pain from liver abscess

-Tx: metronidazole + luminal agent

Pinworms

Enterobius vermicularis, seen in school-age children

-Presentation: nocturnal perianal itching

-Dx: Scotch-tape test

-Tx: Albendazole or pyrantel pamoate

Ascariasis

Ascaris lumbricoides, caused by ingestion of eggs from contaminated soil. Some large worms can cause small-bowel obstruction

-Tx: albendazole

Hookworm

Necator/Ancylostoma, barefoot exposure to contaminated soil

-Presentation: iron deficiency anemia

-Tx: albendazole

Toxoplasmosis

Toxoplasma gondii, seen in patients with cat litter or undercooked meat exposure

-Causes fetal CNS disease in pregnant patients

-HIV/AIDs with CD4 < 100 have ring-enhancing brain lesions

-Tx: pyrimethamine + sulfadiazine + leucovorin (PSL)`

Praziquantal

What agent is used for flukes and tapeworms?

Chlamydia and Gonorrhea

The CDC recommends annual screening of all sexually active women <25 for what two STDs?

Expedited partner therapy

Besides treating the patient, what is indicated after a diagnosis of gonorrhea or chlamydia?

Trichomoniasis

Trichomonas vaginalis

-Presentation: frothy, malodorous, yellow-green vaginal discharge plus a “strawberry” cervix

-Dx: NAAT or wet mount with motile flagellated trophozoites

-Tx: Metronidazole + partner treatment

HPV

Anogenital warts (6, 11), cervical/anal/oropharyngeal cancer (16, 18)

-Tx: cryotherapy, imiquimod for warts

-Prevention: HPV vaccine

HIV

What screening is indicated at least once for all patients 13-64 years old?

PrEP

What is indicated for high-risk HIV-negative patients?

Syphilis

What screening is indicated in pregnancy, men who have sex with men, and those who are HIV-positive?

Doxycycline

Treatment of choice for chlamydia trachomatis?

Ceftriaxone

Treatment of choice for neisseria gonorrhea?

PCN G

Treatment of choice for syphilis?

Doxycycline

Treatment of choice for mycoplasma genitalium?

Lyme Disease

Borrelia burgdorferi, spread by Ixodes tick (deer tick)

-Presentation: erythema migrans, low-grade fever, chills, headache, fatigue, mylagia, lymphadenopathy, disseminated disease (flu like syndrome), and chronic disease (arthritis)

-Dx: EIA or IFA then confirmatory western blot

-Tx: doxycycline

Doxycycline

What is indicated for Lyme disease prophylaxis in a patient if the tick was attached for >36 hours and/or engorged and <72 hours since removal in an endemic area?

Rocky Mountain Spotted Fever

Rickettsia rickettsii, seen most in the Carolinas and Oklahoma

-Presentation: fever + headache + petechial rash starting on wrists/ankles that spreads centrally to palms and soles

-Tx: doxycycline

Babesiosis

Babesia microti, often a coinfection with Lyme disease, and seen in northeastern US

-Presentation: fever, hemolytic anemia, “Maltese cross” on smear

-Tx: Azithromycin + atovaquone

Tularemia

Francisella tularensis, from ticks or rabbits

-Tx: streptomycin or gentamicin

Malaria

Plasmodium falciparum, seen in patients who have traveled to endemic regions

-Presentation: cyclical fevers, hemolysis, thrombocytopenia

-Dx: thick and thin blood smears

-Tx: artemisinin-based combination therapy

Bartonellosis

Cat-scratch disease

-Presentation: regional LAD after a cat scratch

-Tx: azithromycin

COVID-19

Respiratory illness caused by SARS-CoV-2, which is spread primarily by droplets and aerosols

-RF: age > 65, obesity, diabetes, CV disease, CKD, immunocompromise, pregnancy, unvaccinated

-Presentation: fever, dry cough, fatigue, headache, congestion, anosmia, ageusia, nausea

-Dx: NAAT/RT-PCR

-Tx: high-risk needs Paxlovid within 5 days, dexamethasone if needing O2 in hospital, anticoagulation if hospitalized

Long COVID

Fatigue, brain fog, dyspnea, POTS, or persistent loss of smell that can last weeks to months after COVID

Mononucleosis

Viral illness characterized by classic triad of fever + LAD + pharyngitis + atypical lymphocytes, transmitted via oropharyngeal secretions and saliva

-Dx: heterophile antibody screen (Monospot), atypical lymphocytes with enlarged nuclei on smear, splenomegaly or LUQ pain, maculopapular rash

-Tx: supportive, steroids in severe cases, avoid contact sports for > 3-4 weeks due to risk of splenic rupture

HSV

Double-stranded DNA virus that establishes lifelong latency in sensory ganglia, can be orolabial or genital, and is spread via direct mucosal/skin contact

-Presentation: prodrome of tingling/burning → grouped vesicles on an erythematous base → painful ulcers often with fever, malaise, and tender LAD. Recurrences are milder, shorter, and often without systemic symptoms

-Dx: HSV PCR or lesion swab

-Tx: valacyclovir

HSV Keratitis

Dendritic ulcer on fluorescein staining, ophthalmologic emergency

-Avoid steroids

36 weeks

When should suppressive therapy for HSV be started in pregnancy?

Shingles

Reactivation of latent varicella zoster virus (VZV) in a sensory dorsal root or cranial nerve ganglion

-Presentation: painful grouped vesicles on an erythematous base in a unilateral dermatomal distribution that does not cross the midline. Can also present as ophthalmicus (V1 distribution with + Hutchinson sign), Ramsay Hunt syndrome (facial palsy, vesicles in ear canal), and postherpetic neuralgia

-Dx: PCR

-Tx: valacyclovir within 72 hours of rash onset

-Prevention: Shingrix vaccine

HIV

RNA retrovirus that depletes CD4+ T-lymphocytes, which is transmitted from sexual contact, blood, and perinatally

-Presentation: fever, LAD, pharyngitis, rash, myalgias

-Dx: fourth generation HIV-1/2 antibody/antigen combo immunoassay, HIV RNA viral load, CD4 count, genotype resistance testing

-Tx: ART therapy (bictegravir/tenofovir alafenamide/emtricitabine), avoid breast feeding

72 hours

Post-exposure prophylaxis should be started within what time of HIV exposure?

PrEP

What should be started in HIV-negative patients with ongoing significant risk like men who have sex with men, serodiscordant patients, and IV drug users?

<200

What CD4 count is associated with PJP?

<150

What CD4 count is associated with Histoplasmosis in endemic areas?

<100

What CD4 count is associated with Toxoplasmosis and Cryptococcus?

<50

What CD4 count is associated with Mycobacterium avium complex?

Azithromycin

What is the treatment of choice for MAC?

Influenza

Viral respiratory infection caused by orthomyxovirus resulting in fever, coryza, cough, headache, and malaise

-Dx: usually clinical or rapid antigen test in clinic. Everyone aged > 6 months should receive annual influenza vaccine

-Tx: oseltamivir if high risk patients