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• Entamoeba histolytica Protazoa.- Transmission: Cysts in water Amebiasis – 1-4 weeks of bloody diarrhea (dysentery), liver abscess ("anchovy paste" exudate), usually a single liver abscess in the right lobe, RUQ pain. Diagnosis: Serology, antigen testing, and/or trophozoites (with engulfed RBCs in the cytoplasm) or cysts with up to 4 nuclei in stool.- Histology of colon biopsy shows flash-shaped ulcers. Treatment: Metronidazole; paromomycin or iodoquinol for asymptomatic cyst passers.
• Cryptosporidium Protazoa.- Severe diarrhea in AIDS- Mild disease (watery diarrhea) in immunocompetent hosts - Transmission: Oocysts in water Diagnosis: Oocysts on acid-fast stain, antigen detection Treatment: Nitazoxanide in immunocompetent hosts- Prevention by filtering city water supplies.
• Naegleria fowleri Protazoa.- Transmission: Swimming in freshwater lakes; enters via cribriform plate. - Rapidly fatal meningoencephalitis Diagnosis: Amoebas in CSF. Treatment: Amphotericin B has been effective for a few survivors.
• Trypanosoma brucei Protazoa.- Transmission: Tsetse fly, a painful bite (vs Trypanosoma cruzi) African sleeping sickness – enlarged lymph nodes, recurring fever (due to antigenic variation), meningoencephalitis, somnolence, coma.- Two subspecies: Trypanosoma brucei rhodesiense/gambiense Diagnosis: Trypomastigote in blood smear Treatment: Suramin for blood-borne disease or melarsoprol for CNS penetration ("I am sure melanin helps with sleep.")
• Plasmodium Malaria – fever, headache, anemia, splenomegaly, GI symptoms P. vivax/ovale – 48-hour cycle, dormant form (hypnozoite) in liverP. falciparum – severe, irregular fever patterns; parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs P. malariae – 72-hour cycle - Transmission: Anopheles mosquito Diagnosis: - Thick and thin blood smear: trophozoite ring form within RBC, schizont containing merozoites- Red granules (Schüffner stippling) throughout RBC cytoplasm seen with P vivax/ovale Treatment: - Chloroquine (blocks Plasmodium heme polymerase).- If resistant, use mefloquine or atovaquone/proguanil. - If life-threatening, use intravenous quinidine or artesunate (test for G6PD deficiency).- For P vivax/ovale, add primaquine for hypnozoite (test for G6PD deficiency).
• Babesia Babesiosis – fever and hemolytic anemia.- Predominantly in northeastern United states- Asplenia ↑ risk of severe disease. - Transmission: Ixodes tick (same as Borrelia burgdorferi) Diagnosis: Blood smear; ring form, "Maltese cross", PCR Treatment: Atovaquone + azithromycin
• Leishmania donovani - Transmission: sandfly Cutaneous leishmaniasis – reddish macules/papules that develop central ulceration Visceral leishmaniasis (kala-azar) – spiking fevers, hepatosplenomegaly, pancytopenia, darkened skin Diagnosis: Macrophages containing amastigotes Treatment: Amphotericin B, sodium stibogluconate
• Trichomonas vaginalis Anaerobic, motile protazoan with flagella- Transmission: sexual (cannot exist outside human because it cannot form cysts) Vaginitis – foul-smelling, yellow or green discharge; itching and burning.- In male patients, this organism can cause urethritis, although it is often asymptomatic. Diagnosis: - Motile, flagellated trophozoites on wet mount (saline microscopy)- Cervical punctations ("strawberry cervix")- Vaginal pH >4.5 (elevated) - Treatment: Metronidazole for patient and partner
• Trichuris trichura (whipworm) Nematode (roundworm) Transmission: fecal-oral. Clinical features:- Often asymptomatic- Loose stools, anemia- Rectal prolapse in children Treatment: Bendazoles
• Echinococcus granulosus Cestode (tapeworm) Transmission: Ingestion of eggs in food contaminated with dog feces- Sheep are intermediate host Cystic echinococcosis:- Hydatid cysts in liver ("eggshell calcification"); cysts can rupture can cause anaphylaxis.- Hepatomegaly → RUQ pain Treatment: Albendazole
• Clonorchis sinensis Trematode (fluke) Transmission: undercooked fish Clinical features:- Biliary tract inflammation → pigmented gallstones- Associated with cholangiocarcinoma Treatment: Praziquantel
• Ectoparasites Scabies (Sarcoptes scabiei)- Common in children, crowded populations (jails, nursing homes)- Mites that burrow into the stratum corneum and cause pruritus (worse at night)- Serpiginous burrows (lines) in webspace of hands and feet- Transmission through skin-to-skin contact or via fomites- Treatment: permethrin cream, washing/drying all clothing/bedding, treat close contacts. Lice (Pediculus humanus/Phthirus pubis)- Blood-sucking insects- Cause intense pruritus with associated excoriations- Commonly on scalp and neck (head lice) or waistband and axilla (body lice)- Can transmit Rickettsia prowazekii (epidemic typhus), Borrelia recurrentis (relapsing fever), Bartonella quintana (trench fever)- Treatment: pyrethroids, malathion, ivermectin lotion, nit combind. 
• Haemophilus ducreyi Transmission: sexual transmission and direct contact - Chancroid- Soft, painful genital ulcer with exudate- Slow to heal without treatment- Inguinal adenopathy Diagnosis: DNA probe, 'school of fish' appearance on Gram stain Treatment: azithromycin, ceftriaxone, or ciprofloxacin
• Histoplasmosis Dimorphic fungus. Environmental form: hyphae with microconidia. Tissue form: intracellular yeasts, no capsule.  Location: Mississippi and Ohio River Valleys- Found in soil with bird (eg, starlings) or bat droppings Pathology: Macrophages filled with dimorphic fungus with septate hyphae. Symptoms:- Palatal/tongue ulcers- Splenomegaly- Lesions have a tendency to calcify after they heal. Diagnosis: Positive urine and serum polysaccharide antigen test.  Treatment: Itraconazole for mild, amphotericin B for severe
• Blastomycosis Dimorphic fungus. Location: Eastern and Central US Pathology: Broad-based budding of Blastomyces (same size as RBCs) Symptoms:- Inflammatory lung disease- Can dissiminate to skin/bone- Verrucous skin lesions can simulate SCC- Forms granulomatous nodules Treatment: Fluconazole/itraconazole for local infection; amphotericin B for systemic disease.
• Coccidioidomycosis Dimorphic fungus. Location: Southwestern US, California- Found in desert sand Pathology: Spherule filled with endospores of Coccidioides Disease: Valley fever- Flu-like illness or pneumonia- Dissiminates to skin/bone→ Erythema nodosum (desert bumps)→ Arthralgias (desert rheumatism)- Can cause meningitis- Pulmonary lesions have a tendency to calcify after they heal.
• Paracoccidioidomycosis Location: Latin America Pathology: Budding yeast of Paracoccidoides with "captain's wheel" formation Clinical presentation: Similar to blastomycosis- Acute pneumonia- Painful nasal, pharyngeal, and laryngeal mucosal ulcerations- Cervical lymphadenopathy- Can disseminate to skin/bones (including verrucous skin lesions) Treatment: Itraconazole or amphotericin B for systemic disease.
• Tinea (dermatophytes) Cutaneous mycosis Dermatophytes include Trichophyton, Epidermophyton, Microsporum.- Branching septae hyphae visible on KOH preparation with blue fungal stain.- Associated with pruritus. Tinea capitis: Occurs on head, scalp. Associated with lymphadenopathy, alopecia, scaling.Tinea corporis: Occurs on torso. Characterized by erythematous scaling rings ("ringworm") and central clearing. Can be acquired from contact with an infected cat or dog.Tinea cruris: Occurs in inguinal area. Often does not show the central clearing seen in tinea corporis.Tinea pedis: Interdigital (most common), moccasin distribution, vesciular type.Tinea unguinum: Onchomycosis; occurs on nails.
• Pityriasis versicolor Caused by Malassezia spp., a yeast-like fungus - Degradation of lipids produces acids that damage melanocytes and cause hypopigmented, hyperpigmented, and/or pink patches - More common in summer; moist, warm climates - "Spaghetti and meatball" appearance on microscopy- Coppery-orange fluorescence under Wood lamp (UV) Treatment: selenium sulfide
• Mucor and Rhizopus spp. Irregular, broad, nonseptate hyphae branching at wide angles. Mucormycosis- Mostly in ketoacidotic diabetic and/or neutropenic patients (eg, leukemia).- Inhalation of spores → fungi proliferate in blood vessel walls, penetrate cribriform plate, and enter brain.- Rhinocerebral, frontal lobe abscess; cavernous sinus thrombosis.- Headache, facial pain, black necrotic eschar on face.- May have cranial nerve involvement. Treatment: surgical debridement, amphotericin B or isavuconazole
• Nematode routes of infection Ingested:- Enterobius- Ascaris- Toxocara- Trichinella Cutaneous:- Strongyloides- Ancylostoma- Necator Bites:- Loa loa (deer, horse, mango flies)- Onchocerca volvulus (blackflies)- Wuchereria bancrofti (mosquito)
• Parasite hints Biliary tract disease, cholangiocarcinoma - Chlonorchis sinensis Brain cysts, seizures - Taenia solium (neurocysticercosis) Hematuria, squamous cell bladder cancer - Schistosoma haematobium Liver (hydatid cysts) - Echinococcus granulosus Microcytic anemia - Ancylostoma, Necator Myalgias, periorbital edema - Trichinella spiralis Perianal pruritus - Enterobius Portal hypertension - Schistosoma mansoni/japonicum Vitamin B12 deficiency - Diphyllobothrium latum
• Wuchereria bancrofti Nematode (roundworm) Transmission: Female mosquito- Symptom onset after 9 months-1 year. - Lymphatic filariasis (elephantiasis) – worms invade lymph nodes → inflammation → lymphedema. Treatment: Diethylcarbamazine
• Cell walls Unique to gram + bacteria:- Lipoteichonic acid Unique to gram - bacteria:- Outer membrane- Endotoxins, lipopolysaccharides- Porines- Periplasmatic space
• Bacterial taxonomy Spherical (coccus):- Gram ⊕: Staphylococcus (clusters), Streptococcus (chains or pairs), Enterococcus (pairs or short chains)- Gram ⊝: Moraxella catarrhalis, Neisseria Rod:- Gram ⊕: Bacillus, Clostridium, Corynebacterium, Gardnerella (gram variable), Lactobacillus, Listeria, Cutibacterium (formerly Propionibacterium), Mycobacterium (acid fast)- Gram ⊝: Enterics: Bacteroides, Campylobacter, E coli, Enterobacter, Fusobacterium, Helicobacter, Klebsiella, Proteus, Pseudomonas, Salmonella, Serratia, Shigella, Vibrio, YersiniaRespiratory: Acinetobacter baumanii, Bordetella, Burkholderia cepacia, Haemophilus (pleomorphic), Legionella (silver stain)Zoonotic: Bartonella, Brucella, Francisella, Pasteurella Branching filamentous: Actinomyces, Nocardia (weakly acid fast) Pleomorphic (no cell wall):- Gram ⊝: Anaplasma, Erlichia, Chlamydiae (Giemsa), Rickettsiae (Giemsa), Mycoplasma (contains sterols, which do not Gram stain), Ureaplasma Spiral:- Spirochetes, gram ⊝: Borrelia (Giemsa), Leptospira, Treponema
• Gram stain Bacteria with thick peptidoglycan layer retain crystal violet dye (gram ⊕); bacteria with thin peptidoglycan layer turn pink (gram ⊝) with counterstain. Do not stain well:- Treponema, Leptospira – Too thin to be visualized.- Mycobacteria – Cell wall has high lipid content.- Mycoplasma, Ureaplasma – No cell wall.- Legionella, Rickettsia, Chlamydia, Bartonella, Anaplasma, Ehrlichia – Primarily intracellular; also, Chlamydia lack classic peptidoglycan because of ↓ muramic acid).
• Giemsa stain - Chlamydia- Borrelia- Rickettsia- Trypanosomes- Plasmodium
• Periodic-acid-Schiff stain Stains glycogen, mucopolysaccharides. - Used to diagnose Whipple disease (Tropheryma whipplei).
• Ziehl-Neelsen stain (carbol fuchsin) Acid-fast bacteria (eg, Mycobacteria, Nocardia; stains mycolic acid in cell wall); protozoa (eg, Cryptosporidium oocytes). - Auramine-rhodamine stain is more often used for screening (inexpensive, more sensitive).
• India ink stain Cryptococcus neoformans - Mucicarmine can also be used to stain thick polysaccharid capsule red.
• Silver stain - Fungi (eg, Coccidioides, Pneumocystis jirovecii)- Legionella- Helicobacter pylori
• Special culture requirements H influenzae – Chocolate agar (Factors V [NAD+] and X [hematin]) N gonorrhoeae, N meningitidis – Thayer-Martin agar (Selectively favors growth of Neisseria by inhibiting growth of gram ⊕ bacteria with Vancomycin, gram ⊝ bacteria with Trimethoprim and Colistin and fungi with Nystatin) Bordatella pertussis - Bordet-Gengou agar (potato extract), Regan-Lowe medium (charcoal, blood, and antibiotic) Corynebacterium diphtheriae - Tellurite agar, Löffler medium Mycobacterium tuberculosis - Löwenstein-Jensen agar Mycoplasma pneumoniae - Eaton agar (requires cholesterol) Lactose fermenting enterics - MacConkey agar (fermentation produces acid, causing colonies to turn pink) E coli - Eosin-methylene blue (EMB) agar (colonies with green metallic sheen) Legionella - Charcoal yeast agar buffered with cysteine and iron Fungi - Sabouraud agar
• Bugs with exotoxins Diphtheria toxin (Corynebacterium diphtheriae), exotoxin A (Pseudomonas aeruginosa): Inactivate elongation factor (EF-2). Shiga toxin (Shigella), shiga-like toxin (EHEC): Inactivate 60S ribosome by removing adenine from rRNA Heat-labile toxin (ETEC): Overactivates adenylate cyclase (↑ cAMP) → ↑ Cl- secretion in gut and H2O efflux.Heat-stabile toxin (ETEC): Overactivates guanylate cyclase (↑ cGMP) → ↓ reabsorption of NaCl and H2O in gut. Edema toxin (Bacillus anthracis): Mimics adenylate cyclase (↑ cAMP). Cholera toxin (Vibrio cholerae): Overactivates adenylate cyclase (↑ cAMP) by permanently stimulating Gs → ↑ Cl- secretion in gut and H2O efflux. Pertussis toxin (Bordatella pertussis): Overactivates adenylate cyclase (↑ cAMP) by disabling Gi, impairing phagocytosis to permit survival of microbe. Tetanospasmin (C tetani), Botulinum toxin (C botulinum): Proteases that cleave SNARE (soluble NSF attachment protein receptor), a set of proteins required for neurotransmitter release via vesicular fusion. Alpha toxin (Clostridium perfringens): Phospholipase (lecithinase) that degrades tissue and cell membranes. Streptolysin O (Streptococcus pyogenes): Protein that degrades cell membrane. Toxic shock syndrome toxin (TSST-1) (S aureus), erythrogenic exotoxin A (Streptococcus pyogenes): Cross-links β region of TCR to MHC class II on APCs outside of the antigen binding site → overwhelming release of IL-1, IL-2, IFN-γ, and TNF-α → shock.
• Endotoxin LPS found in outer membrane of gram ⊝ bacteria. Composed of O-antigen + core polysaccharid + lipid A (the toxic component). Released upon cell lysis or by living cells by blebs detaching from outer surface membrane (vs exotoxin, which is actively secreted). Three main effects:1. Macrophage activation (TLR4/CD14) → TNFα, IL-1, IL-6, NO2. Complement activation → C3a, C5a3. Tissue factor activation → Coagulation cascade → DIC
• Nocardia vs. Actinomyces Both are gram ⊕ and form long, branching filaments resembling fungi Nocardia:- Aerob- Acid fast (weak)- Found in soil- Pulmonary infections in immunocompromised (can mimic TB but with Θ PDD)- Cutaneous infections after trauma in immunocompetent- Can spread to CNS Actinomyces:- Anaerobe- Not acid fast- Normal oral, reproductive, and GI flora- Causes oral/facial abscesses that drain through sinus tracts- Often associated with dental caries/extraction and other maxillofacial trauma- Forms yellow "sulfur granules"- Can also cause PID with IUDs Treatment:- Nocardia: Sulphonamides - Actinomyces: Penicillin
• Salmonella Gram ⊝ rod. Non-lactose fermenter, oxidase ⊝. Can invade the GI tract via M cells of Peyer patches. Flagellated. Produce H2S, motile. Salmonella typhi:- Human reservoir only- Can disseminate hematogenously- Virulence factor: Endotoxin, Vi capsule → extensive intracellular replication in macrophages → spread through lymphatics and RES.- Monocytic response- Causes typhoid fever (rose spots on abdomen, constipation, abdominal pain, fever)- Treat with ceftriaxone or fluoroquinolone- Oral vaccine contains live attenuated S typhi, IM vaccine contains Vi capsular polysaccharide- Carrier state with gallblader colonization Salmonella spp:- Human and animals (poultry, eggs, pets, turtles)- Can disseminate hematogenously- Enterocolitis/gastroenteritis. Second most common bacterial cause after Campylobacter. 6-48 hour incubation; nausea and vomiting; only occasionally bloody, loose stools; fever; abdominal pain; myalgia; headache- Septicemia, osteomyelitis (in patients with sickle cell disease)- Inflammatory response marked by neutrophil infiltration (PMN response)- Antibiotics prolong duration, not indicated
• Shigella Gram Θ rod. Non-lactose fermenter, oxidase Θ. Reservoir: Human colon onlyTransmission: fecal-oral spread. Low infectious dose (vs. Salmonella - high). Pathogenesis:- Invasion of M cells, create very shallow ulcers.- Shiga toxin: inhibit protein synthesis by clipping 60S ribosomal subunit. Disease:- Fever (generally >101.0˚F)- Lower abdominal cramps, tenesmus- Diarrhea: first watery, then bloody- Invasive but rarely causes septicemia Treatment: Mild – supportive; Severe – Quinolones
• Tick-borne illnesses Ehrlichosis:- Ehrlichia, vector is tick.- Monocytes with morulae in cytoplasm. Anaplasmosis:- Anaplasma, vector is tick.- Granulocytes with morulae in cytoplasm. Q fever:- Coxiella burnetii, no arthropod vector.- Spores inhaled as aerosoles from cattle/sheep amniotic fluid.- Common cause of culture ⊝ endocarditis. Rocky Mountain spotted fever: - Rickettsia rickettsii, vector is tick. 
• Bugs causing food-borne illness S aureus and B cereus food poisoning starts quickly and ends quickly B cereus - Reheated rice C botulinum - Improperly canned foods (toxins), raw honey (spores) C perfringens - Reheated meat E coli - Undercooked meat L monocytogenes - Deli meats, soft cheeses Salmonella - Poultry, meat, eggs S aureus - meats, mayonnaise, custard (preformed toxin)
• Bugs causing diarrhea Bloody diarrhea- Campylobacter - comma-shaped, grow at 42°C- Salmonella- Shigella- EHEC, EIEC- Y enterocolitica - day care outbreaks, pseudoappendicitis- Entamoeba histolytica - protozoan; amebic dysentery; liver abscess Watery diarrhea- C difficile - pseudomembranous colitis- C perfringens - also causes gas gangrene- ETEC - Travelers' diarrhea- Protozoae - Giardia, Cryptosporidium- V cholerae- Viruses - rotavirus, norovirus, adenovirus
• Common causes of pneumonia Neonates: Group B streptococci, E. coliChildren: Mycoplasma, C trachomatis/pneumoniae, S pneumoniaeAdults: S pneumoniae, H influnzae, anaerobes, viruses (eg, influenza)Elderly: S pneumoniae, influenza, anaerobes Alcoholics: Klebsiella, anaerobes usually due to aspirationAspiration: AnaerobesDrug users: S pneumoniae, S aureusImmunocompromised: S aureus, gram - rods, fungi, P jirovecii (with HIV)Cystic fibrosis: PseudomonasNosocomial: S aureus, PseudomonasPostviral: S pneumoniae, S aureus, H influenzae Atypical: Mycoplasma, Chlamydia, Legionella
• Common causes of meningitis Neonates: Group B streptococci, E coli, ListeriaChildren: S pneumoniae, N meningitidis, H influenzae B6-60 years: S pneumoniae, N meningitidis (#1 in teens), enteroviruses, HSVElderly: S pneumoniae, Listeria - Give ceftriaxone and vancomycin empirically (add ampicillin if Listeria is suspected) Viral causes of meningitis: enteroviruses (esp coxsackievirus), HSV-2, HIV, VZV, West-Nile virus In HIV: Cryptococcus 
• Infections causing brain abscess Most commonly viridans streptococci and Staphylococcus aureus - Multiple abscesses are usually from bacteremia- single lesions from contiguous sites: otitis media and mastoiditis --> temperal lobe and cerebellum- sinusitis or dental infection --> frontal lobe - Toxoplasma reactivation in AIDS
• Osteomyelitis - Assume if no other information is available- S aureus -  - Sexually active - N gonorrhoeae (septic arthritis more common) - Sickle cell disease - Salmonella and S aureus - Prosthetic joint replacement - S aureus or S epidermidis - Vertebral involvement - S aureus or Mycobacterium tuberculosis (Pott disease) - MRI is best for detecting acute infection- Radiographs can be useful in chronic infection
• Urinary tract infections Cystitis presents with dysuria, frequency, urgency, subrapubic pain, and WBCs (but not WBC casts) in urine - Males: infants with congenital defects, vesicourethral reflux- Elderly: enlarged prostate Ascension to kidney results in pyelonephritis, which presents with fever, chills, flank pain, costovertebral angle tenderness, hematuria, and WBC casts - F:M = 10:1 - Predisposing factors: obstruciton, kidney surgery, catherization, GU malformation, diabetes, pregnancy
• UTI bugs E coli: Leading cause of UTI. Colonies show green metallic sheen on EMB agar Staphylococcus saphrolyticus: 2nd leading cause of UTI in sexually active women Klebsiella pneumoniae: 3rd leading cause of UTI. Large mucoid capsule. Proteus mirabillis: Motility causes "swarming" on agar; produces urease; associated with struvite stones Diagnostic markers:- Leukocyte esterase = evidence of WBC activity- Nitrate test = reduction of urinary nitrates by bacterial species (E. coli)- Urease test = urease-producing bugs (S saphrolyticus, Proteus, Klebsiella)
• Common vaginal infections Bacterial vaginosis:- No inflammation- thin, white discharge with fishy odor- Clue cells- pH >4.5- Treatment: Metronidazol Trichomonas vaginitis:- Inflammation ("strawberry cervix")- Frothy, yellow-green, foul-smelling discharge- Motile trichomonads- pH >4.5- Treatment: Metronidazol, treat sexual partners Candida vulvovaginitis- Common triggers: Antibiotic use (reduction of lactobacilli popultion), high estrogen levels (eg, pregnancy), systemic corticosteroid therapy, uncontrolled diabetes mellitus, immunosuppresion.- Inflammation- Thick, white, "cottage cheese" discharge- Pseudohyphae- pH normal (4.0-4.5)- Treatment: azoles
• ToRCHeS infections Toxoplasmosa gondii:- Cat feces or ingestion of undercooked meat- Usually asymptomatic; lymphadenopathy- Neonate: Classic triad: chorioretinitis, hydrocephalus, and intracranial calcifications ± blueberry muffin rash Rubella:- Respiratory droplets- Rash, lymphadenopathy, polyarthritis, polyarthralgia- Neonate: Classic triad: abnormalities of eye (cataract) and ear (deafness) and congenital heart disease (PDA), ± blueberry muffin rash Cytomegalovirus:- Sexual contact, organ transplants- Usually asymptomatic, mononucleosis-like symptoms- Neonate: hearing-loss, seizures, petechial rash "blueberry muffin" rash, periventricular calcifications HIV:- sexual contact, needlestick Herpes simplex virus-2:- Skin or mucous membrane contact- Neonate: Meningoencephalitis, herpetic (vesicular) lesions Syphilis:- Sexual contact- Chancre (1°) and disseminated rash (2°) are likely to result in fetal infection- Neonate: Stillbirth, hydrops fetalis, facial abnormalities (eg, notched teeth, saddle nose, short maxilla), deafness
• Red rashes of childhood Coxsackievirus type A: Hand-foot-mouth disease.- Oval-shaped vesicles on palmes and soles; vesicles and ulcers in oral mucosa Human herpesvirus 6: Roseola (exanthema subitum)- Asymptomatic rose-colored macules appear on body after high fever Measles virus: Measles (rubeola)- Confluent rash beginning at head and moving down; preceded by cough, coryza, conjunctivitis, and Koplic spots on buccal mucosa Parvovirus B19: Erythema infectiosum (fifth disease)- "Slapped cheek" rash on face (can cause hydrops fetalis in pregnant women) Rubella virus: Rubella (German measles)- Pink macules and papules begin at head and move down, remain discrete Streptococcus pyogenes: Scarlet fever- Erythematous, sandpaper-like rash with fever and sore throat Varizalla-Zoster virus: Chickenpox- Vesicular rash begins on trunk; spreads to face and extremities with lesions of different stages
• Red rashes of childhood Coxsackievirus type A: Hand-foot-mouth disease.- Oval-shaped vesicles on palmes and soles; vesicles and ulcers in oral mucosa Human herpesvirus 6: Roseola (exanthema subitum)- Asymptomatic rose-colored macules appear on body after high fever; can present with febrile seizures Measles virus: Measles (rubeola)- Confluent rash beginning at head and moving down; preceded by cough, coryza, conjunctivitis, and Koplic spots on buccal mucosa Parvovirus B19: Erythema infectiosum (fifth disease)- "Slapped cheek" rash on face (can cause hydrops fetalis in pregnant women) Rubella virus: Rubella (German measles)- Pink macules and papules begin at head and move down, remain discrete Streptococcus pyogenes: Scarlet fever- Erythematous, sandpaper-like rash with fever and sore throat Varizalla-Zoster virus: Chickenpox- Vesicular rash begins on trunk; spreads to face and extremities with lesions of different stages

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