Differential diagnosis Respritory system

Q Fever  Coxiella brunetii

G(-)R

Reservoir in cattle, sheep, and goats

Transmitted by inhalation, unpasteurized milk, aerosols

Low ID50

Fever, chills, chest pain, nonproductive cough, GI issues, weight loss, fatigue

occasional complications like endocarditis

can be acute or chronic

Primary typical Pneumonia Streptococcus penumonia

G(+) C

Droplet, fomites, droplets

Human Reservoir

Treated by antibiotics and vacciene exists MMR

infected alveoli of lung fill with fluids; interferes with oxygen uptake, High fever, breathing difficulty, chest pains 

Hib Pneumonia Haemophilus influenzae

G(-) Coccobacillus Rod

Droplet transmission

Human reservoir

Antibiotics and Hib Vaccine

Fever, cough, shortness of breath, chest pain, fatigue or malaise, chills, rapid breathing, crackles or rales, possible cyanosis

Walking pneumoniae Mycoplasma pneumoniae

direct contact, fomites, droplets, vehicle in water

reservoir in humans and water

treated by antibiotics

common in children and young adults on college campuses

symptoms include mild but persistent respiratory symptoms, low fever, persistent cough, headache

Legionellosis Legionella pneumiophila 

G(-)R

Vehicle in water

Reservoir in water

treated by antibiotics

occurs in air conditioning towers, hot water systems, ice machine s

chlorine resistant

high fever, dry or productive cough, shortness of breath, muscle aches and fatigue, headache, nasuea, vomiting, diarrhea, confusion or altered mental status, chest pain

common in older adults, smokers, chronic lung disease

can co-present with pontiac fever

Pertussis (whooping cough) Bordetella pertussis

G(-) coccobacillus

direct contact, fomites, droplets

human reservoir

Tdap vaccine

treated by antibiotics

Also known as 100 day cough

common in small children and infants
Stage 1: Catarrhal stage, like common cold

Stage 2: Paroxysmal stage: Violent coughing sieges

Ciliary action compromised mucus accumulates

Gasping for air b/w coughs causes a “whooping” sound

Coughing episodes can occur for 1-6 weeks

Stage 3: Convalescence stage

May last for months

Mortality may be high in infants

apnea

Psitacosssis (Ornothosis) Chlamydia psittaci

: G(-)R

Intracellular bacterium

direct contact, fomites, droplet (transmitted by elementary bodies from bird droppings)

Animal reservoir (parrots, pigeons, parakeets)

treated by antibiotics

headache, dry cough, dyspnoea, chills, pneumonia, fever, splemomegaly, myalgia

Pneumocystis Pneumonia Pneumocystis jiroveci    

fungal/protasoan infection

droplet transmission

human reservoir

treated by timethoprim

Fever, dry cough, dyspnea (esp. in HIV/AIDS patients)

Mellioidosis Burkholderia pseudomallei

Gram(-)R

Direct contact

Reservoir in soil and water

treated by antibiotics

Pneumonia, abscesses, septicemia, can reactivate years later

Common in SE Asia & Australia; often misdiagnosed

RSV Respiratory Syncytial Virus

(RNA Virus)

direct contact, fomites, droplets

human reservoir

Ribavirin + Ig for infants w/ lung problems (anti-viral)

Prophylaxis for High-Risk Groups (Palivizumab) (antibody

common in infants Cough, wheezing, fever;

Influenza Influenza virus types A,B,C

(RNA Virus)

direct contact, fomites, droplets

human, ducks, geese reservoir

seasonal vaccine

chills, fever, headache, and muscle aches

Type A: causes pandemics and antigenic shift (major changes)

Type B: causes seasonal outbreaks

Type C: mild and rare

COVID-19 SARS-CoV-2

(RNA Virus)

Humans, zoonotic origin

Treated by Paxlovid, Remdesivir; multiple vaccines

Fever, dry cough, fatigue

Shortness of breath, loss of taste/smell

Sore throat, muscle aches, chills

Diarrhea, nausea

Severe cases: pneumonia, ARDS (Acute Respiratory Distress Syndrome), blood clots, multi-organ failure

loss of smell and taste

Epiglottitis Haemophilus influenzae type b

Gram (-) coccobacilli

Droplet

Human reservoir

antibiotics Ceftriaxone

Hib vaccine

Drooling, fever, sore throat, tripod position in infants, Dysphagia, fever, sorethroat  

Waxy colonies on agar 

Strep Throat Streptococcus pyogenes

 G(+) cocci in chains

direct contact, droplets

human reservoir

antibiotics

Swollen uvula, petechiae on roof of mouth, inflamed tonsils with white spots, gray spots on tongue, otitis media is a complication

Scarlet fever Streptococcus pyogenes

G(+) cocci in chains

transmitted by droplets or direct contact

Human reservoir

high fever, macular spotted rash, strawberry tongue, effected skin frequently peels rhematic fever kidney issues

caused by a exotoxin

Diphtheria Corynebacterium Diptheriae

G(+) R

Direct contact, droplets

human reservoir

antibiotics and Tdap vaccine

Sore throat, fever, general malaise and swelling of neck

Thick gray pseudo membrane

Diagnosed by:

Exotoxin leading to a thick coating of the nose and throat

Usually fuzzy black or gray

Intoxication (double vision slurred speech)

Show signs of going into shock

Otitis Media 

Secondary to upper respiratory infections via the Eustachian tube

human reservoir

treated by antibiotics

ear pain, hearing loss, irritability in children, fever, and fluid buildup behind eardrum

Common Cold Rhinoviruses (~50%) Coronaviruses (15–20%)

droplets, direct contact, fomites

reservoir in humans

Sneezing, runny nose, sore thorat, cough, mild fatigue, low to no fever

Tuberculosis Mycobacterium tuberculosis

Acid-fast rod

droplet nuclei, direct contact, and fomites

reservoir in humans

treated by antibiotics

Latent

No symptoms and cannot spread the disease

Active

Show symptoms and are able to spread

Chronic cough (often bloody)

Weight loss

Night sweats

Fatigue

Chest pain

Histoplasmosis Histoplasma capsulatum

, dimorphic fungus

ihalation of fungal spores, contaminated soil with bat and bird droppings

treated by Amphotericin B

•Not transmitted from human to human

•Symptoms 3-17 days after exposure

•Widespread in Ohio and Mississippi River Valleys

•Diagnosis by culturing fungus

•Those who have a healthy immune system usually Do not have symptoms, or only mild ones.

can leave a person with small scars (granulomas) that are difficult to distinguish from tumors in the lung

Coccidioidomycosis Coccidioides immitis

(dimorphic fungus) 

droplet (transmitted by airborne arthrospores)

reservoir in soil

treated by Amphotericin B

Closely resembles TB

Fever, cough, headache, rash on upper trunk, muscle aches, joint pain in knees/ankles

Advanced symptoms: skin lesions, chronic pneumonia, meningitis, bone/joint infection

C. immitis is one of the most infectious fungal pathogens known

Blastomycosis Blastomyces dermatitidis,

dimorphic fungus

Inhalation of airborne spores from soil and decaying organic matter

reservoir in soil Mississippi Valley, Ohio

treated by Amphotericin B

Generally mild flu-like symptoms and is self-limiting

Can become disseminated in immunocompromised (skin, bones, genitourinary tract)

Chronic cutaneous disease with subcutaneous lesions on the face and hands

Systemic blastomycosis = rare but fatal if untreated

Begins in lungs and can spread rapidly - cutaneous ulcers are common

Chronic form can mimic tuberculosis or lung cancer, with symptoms of low-grade fever, a productive cough, night sweats, and weight loss.

Blastomycosis can also occasionally affect the central nervous system, resulting in meningitis.

Can cause exte

Measles

Virus

Direct contact, Droplet

Human reservoir

MMR Vaccine

Exantham 

High fever

Cough, coryza, conjunctivitis

Koplik spots (red with white center inside of mouth)

Maculopapular rash starting at the hairline and spreading down

Rubella (German Measles)

Virus

Direct contact, droplet

Human reservoir

MMR vaccine

Exantham

Macular rash (Starts on face and spreads downward) and fever

Mild respiratory symptoms

Tender or swollen glands

Risk of Congenital rubella syndrome (CRS)= causes severe fetal damage

Roseola

Virus

Direct or saliva transmission

Human reservoir

Exantham

No vaccine supportive care

High fever then 3-5 days after a rash over the body occurs and blanches when touched

Most common in children 6mos-3yrs

Fifth disease

Transmission by droplet or direct contact with respiratory secretions

Human reservoir

Supportive care

Slapped cheek rash (bright red cheeks)

Lacy, reticular rash on trunk and limbs

Dangerous in pregnancy

Hand foot mouth disease

Virus

transmission through direct contact, droplet, fecal oral
Reservoir in humans

Supportive care

Fever w/ sore throat - rash (flat or raised) on hands, feet, mouth, tongue and interior cheeks

Enterovirus 71 - neurological complications – encephalitis, meningitis and polio-like paralysis

Candidiasis

Yeast

Spread by direct contact and may be a result from suppression of competing bacteria by antibiotics

Treated by antifungals

Oral thrush (white plaques) that is painful or bleeding when scraped

Smallpox (Variola) 

virus

Direct contact and droplet

Human reservoir

Vaccine is available

Respiratory route - bloodstream

Exantham

Incubation period 7-17 days (usually 12-14d)

No signs or symptoms, not contagious

Prodromal Phase (2-4 days) - possibly contagious

Fever, Malaise, Severe headache, Nausea, vomiting, Aching body, Sore throat

most contagious stage is the early rash (4 days)

small red spots tounge and mouth – sores

rash spreads all over body, becomes raised bumps that are fluid filled with depression in center (umbilicated) bumps – pustules

scabs form 3 weeks in

person is very contagious until scabs fall off

Monkeypox

Virus \

Direct contact, indirect, droplet Sexual contact

Zoonotic reservoir in humans, rodents, monkeys

Small pox vaccine protects

Skin, mucous membrane, or respiratory tract

Exantham

Central Africa

Fever, chills, headache, swollen lymph nodes (a key feature), followed by a maculopapular rash progressing to vesicles → pustules → scabs; rash may be painful and often involves face, palms, soles, genitals

Less severe than smallpox

Chickenpox (Varicella)

varicella-zoster virus

direct contact, indirect, droplet transmission

Human reservoir

Vaccine available

Respiratory tract

Exantham

Largely a childhood disease, 1st signs occur 10-21 days after contact.

Infection confers lifelong immunity

Latent virus = shingles

Highly contagious (droplets/contact with open sores)

Itchy rash of red papules (small bumps) – vesicles on stomach, back face

Number of vesicles highly variable and very itchy

High fever, headache, cold-like symptoms, vomiting,, diarrhea

More severe for adults and life threatening

Shingles

Herpes zoster

Direct contact

Reactivation of latent virus

Human reservoir

treated by acyclovir and vaccine is available

Virus moves along peripheral nerves to skin

Not exanthem

Lesions similar to chickenpox - distributed about the waist and limited to one side of the body (nerves are unilateral)

Severe burning or stinging pain - VERY PAINFUL!!

Last 3-4 weeks

May persist for months or yrs called post-herpetic neuralgia (after pains)

Older adults

Impetigo

Staphylococcal aureus or streptococcus pyogenes

Direct contact, indirect

Human reservoir

Treated by antibiotics

honey colored crusted lesions usually on face

Breaks in skin

Exantham

STAPH: Thin-walled vesicles that rupture and crust over, spread by autoinoculation

Highly contagious

STREP: Isolated pustules that become crusted and rupture

Toddlers & grade-school children

Spread by contact

Herpes Simplex

Virus

Direct contact with mucosal surfaces

Human reservoir

Treated by acyclovir

Mucous membrane/broken skin

Not exantham

HHV-1 can remain latent in trigeminal nerve ganglia

Respiratory route, infection usually occurs in infancy

Cold sores or fever blisters (vesicles on lips)

Herpes gladiatorum (vesicles on skin)

Herpes whitlow (vesicles on fingers)

HHV-2 can remain latent in sacral nerve ganglia

Sexual contact - genital herpes

Herpes encephalitis (HHV-2 has up to a 70% fatality rate)

Necrotizing fasciitis 

bacterial

Direct contact, water, vector

Human reservoir

Antibiotics

Not exanthem

Treatment: Immediate surgical debridement; broad-spectrum IV antibiotics

Signs/Symptoms: Severe pain disproportionate to appearance, rapid tissue necrosis, fever, systemic toxicity

Erysipelas 

G(+)C

Direct contact

Human reservoir

Antibiotic treatment

Skin and mucous membrane

Dermal layer infected, red patches with raised

margins, local tissue destroyed, sepsis, fever

Exanthem

Toxic Shock Syndrome

Staphylococcus or

streptococcus

G(+)C

Direct contact

Human reservoir

treated by antibiotics

Sunburn rash, life threatening fever, vomiting, shock and organ damage

Folliculitis 

Staphylococcus G(+) C

Direct contact

Reservoir in water

treated by antibiotics

Infection of hair follicles

Not exanthem

Pimples/pustules at hair follicles, redness, swelling

Contaminated water

Pseudomonas dermatitis 

Pseudomonas aeruginosa G(-)R

Transmitted by vehicle water

Reservoir in soild and water

treated by anitibiotics

Self limiting rash  

Most common occur when hot tub water is not cleaned  

Red itchy rash 

Not exanthem 

Otitis externa 

Pseudomonas aeruginosa G(-)R

Vehicle in soil and water

Reservoir in water

Antibiotics

Enter through ear canal through pool or  

contact of water  

Itching, redness, discomfort of ear canal,  

progressing to fever, pain and swelling  

Not exanthem 

Hearing loss  

Acne

Propionibacterium acnes

Direct contact but non transmissible

reservoir in human skin

treated by Topical retinoids, antibiotics

Build up of dead skin and pus forming a

clogged pore

Comedones (white and black heads), papules,

pustules, nodules, or pseudocysts

Not exanthem

Burili Ulcer 

Mycobacterium ulcerans – acid fast rod 

Direct contact Vehicle in water

Rerservoir in soild and water

Antibiotics

Skin  

Painless swelling of leg, arm, face (wherever  

the contaminated water touched) 

Ulcer with necrosis  

Warts

Papillomaviruses 

Direct contact and indirect

Human reservoir

Treated with acyclovir

Minor breaks in the skin, such as cuts or scrapes, direct skin to skin contact

Small raised growth, can be same color or

darker than skin

Ringworm 

Trichophyton, Epidermophyton, microsporum

Direct contact indirect

Human animals dogs, cattle, cat, mice, horses, guinea pigs

Oral griseofluvin

Portal of entry is through the skin

Exanthem

circles, red and scaly patches that might

blister and ooze

Sporotrichosis 

Sporothrix schenkii – fungal

Puncture by contaminated plant material

Non living reservoir in water and food

Treated by Amphotericin B (Fungi)

Through thorn prick or wound  

Subcutaneous ulcers and abscess, may spread  

to larger areas like hand or arm  

Not Exanthem 

Scabies

Sarcoptes scabiei– parasite

Direct contact and indirect

Human reservoir

permethrin cream or malathion lotion
intense itching(especially at night), rash that looks like tiny red lumps,

Burrows in skin

Not exanthem

Pediculosis 

Pediculus humanus – head louse

Direct contact or indirect

Human reservoir

Permethrin

Tickling feeling moving in hair, irritability, difÏculty sleeping, sores on head from scratching 

Not exanthem 

Visible lice or nits

Conjunctivitis 

Haemophilus influenzae G(-)coccobacillus

Direct contact Indirect

Human reservoir

Antibiotics

Hands touch infected eye secretions then hand touch own eyes Inflammation of conjunctiva with purulent discharge No exanthem

Conjunctiva portal of entry

Redness, discharge and itching

Inclusion Conjunctiviti

c.trachomatis G(-)coccobacillus

Direct contact

Human reservoir

Antibiotics

Hand to eye spread of infected genital secretions Mucous discharge, pink/red eyes, itch, crusting of lashes, swollen lids, tearing No exanthem

Ophthalmia Neonatorum 

Bacterial

Direct contact

Human reservoir

Antibiotics

Passed from mother to baby during vaginal delivery Red eye, pus in eye, swollen eyelids, blindness, Not exanthem

Trachoma 

Bacterial

Direct and indirect contact

Human

Antibiotics

Inflammation of conjunctiva and cornea, irritation, excess tears, sensitivity to light, lesions in cornea, leading to blindness 

Not exanthem 

white spots on inner surface of eyelid

Herpetic Keratitis

Herpes simplex virus 1 (HSV-1)

Direct contact

Human reservoir

Acyclovir

Inflammation of conjunctiva and cornea, irritation, excess tears, sensitivity to light, lesions in cornea, leading to blindness

Acanthamoeba Keratitis

Acanthamoeba 
Indirect and vehicle through water

Water reservoir

Metronidazole

The amoeba entering through nose, eye, broken skin or contact lensInflammation and damage to cornea, vision impairment or blindness Not exanthe

Loiasis 

Loa Loa 

vector through deer fly

Human reservoir

Antiparacitcs

Recurring fever and localized Calabar swelling, itching, and. Skin or eye pain during subcutaneous migration of worms