01Approach to the Critical Patient/attcp47

Immediate stabilization

›Airway and oxygenation priorities

›Supplemental oxygen for SpO2 < 94%

›Target SpO2 92-96% in non-hypercapnic patients

›HFNC for moderate hypoxemic respiratory failure

›Rapid escalation if SpO2 unresponsive to high-flow O2

›NIV trial if no contraindication and cooperative patient

›Early intubation for GCS < 12 or respiratory fatigue

›RSI if intubation required

›Ketamine 1.5 mg/kg IV or etomidate 0.3 mg/kg IV for induction

›Succinylcholine 1.5 mg/kg IV or rocuronium 1.2 mg/kg IV

›Hemodynamic resuscitation

›Shock physiology triggers

›SBP < 90 mmHg or MAP < 65 mmHg

›Lactate >= 2 mmol/l

›IV crystalloid bolus 30 ml/kg over 30-60 minutes

›Reassess after each 500 ml aliquot

›Avoid fluid overload in ARDS pattern

›Norepinephrine for refractory hypotension

›Start 0.1-0.2 mcg/kg/min, titrate to MAP >= 65 mmHg

›Add vasopressin 0.03 units/min for norepinephrine-resistant shock

Antibiotic urgency

›Time-to-antibiotic targets

›Doxycycline within 1 hour in severe/septic presentations

›Class I recommendation: tetracycline-class is first-line

›Beta-lactam monotherapy is ineffective for intracellular organism

›Do not delay antibiotics for diagnostic confirmation in critical patients

›Empiric atypical coverage is indicated in severe CAP

02History/hx56

Exposure history

›Avian and poultry contact

›Psittacine birds: parrots, parakeets, cockatiels, macaws

›Recent acquisition or visit to pet store or bird fair

›Contact duration and proximity

›Poultry species: chickens, ducks, turkeys, pigeons

›Backyard flock, farm, or slaughterhouse exposure

›Cleaning coops or handling feathers/droppings

›Wild bird contact

›Dead bird handling

›Bird feeding stations

›50-88% of confirmed cases report avian or poultry contact

›Even brief or indirect exposure is sufficient for transmission

›Incubation period 7-14 days; median 11 days (range 6-22 days)

Symptom characterization

›Classic presentation triad

›High fever often >= 39-39.5 C

›Abrupt onset

›Chills and rigors

›Headache

›Often severe and disproportionate to illness

›Occipital or frontal distribution

›Dry cough with dyspnea

›Cough present in 63% of cases

›Dyspnea in 50%

›Extrapulmonary symptoms

›Neurologic

›Confusion or altered mental status in 36.9%

03Physical Exam/exam47

Vital signs

›Hemodynamic and temperature assessment

›Fever >= 39 C in 94-100% of cases

›High-grade fever is nearly universal

›Hypothermia suggests severe sepsis in immunocompromised

›Relative bradycardia

›Present in approximately 80% of cases

›Classic finding: pulse-temperature dissociation (Faget sign)

›Tachypnea and hypoxia

›RR >= 30 per minute is a severity marker

›SpO2 < 92% on room air requires admission

Pulmonary exam

›Lung auscultation and percussion

›Crackles or rales on auscultation

›May be focal or diffuse depending on extent of infiltrate

›Exam may be deceptively benign relative to imaging extent

›Signs of consolidation

›Dullness to percussion over involved lobe

›Bronchial breath sounds and egophony

›Signs of pleural effusion

›Stony dullness at lung base

›Reduced or absent breath sounds at base

Extrapulmonary findings

›Hepatosplenomegaly

›Classically described in psittacosis

›Hepatic dysfunction in up to 87.5% of cases

›Right upper quadrant tenderness possible

›Horder spots: rare salmon-colored macular rash

04Differential Diagnosis/ddx53

Atypical pneumonia mimics

›Legionella pneumophila

›ICD-10 A48.1 — Legionnaires disease

›Closest clinical mimic of psittacosis

›Both: high fever, systemic symptoms, elevated inflammatory markers

›Distinguishing features favoring Legionella

›More severe cough, higher WBC, higher glucose, hyponatremia

›Water source exposure: cooling towers, plumbing, hot tubs

›Distinguishing features favoring psittacosis

›Relative bradycardia, elevated CK, avian contact history

›Higher hepatic enzyme elevation

›Mycoplasma pneumoniae

›ICD-10 J15.7

›Typically milder illness

›Younger patients, community outbreaks

›Distinguishing features

›Less systemic inflammation, walking pneumonia pattern

›Cold agglutinins positive in subset

›Chlamydia pneumoniae

›ICD-10 J16.0

›No avian exposure link

›Gradual onset, often pharyngitis prodrome

Other infectious mimics

›Q fever (Coxiella burnetii)

›ICD-10 A78

›Livestock exposure: cattle, sheep, goats rather than birds

›Prominent hepatitis, thrombocytopenia

›Distinguishing features

05Laboratory Tests/lt76

Inflammatory and severity markers

›Complete blood count

›Lymphopenia: characteristic and prognostic

›Reduced lymphocyte percentage is severity predictor

›WBC normal or mildly elevated (differs from bacterial CAP)

›Neutrophilia may coexist with relative lymphopenia

›CRP and inflammatory cascade

›CRP markedly elevated: mean approximately 175 mg/L

›Disproportionately elevated relative to WBC count

›Serial CRP useful for treatment response monitoring

›ESR elevated

›Procalcitonin elevated

›Often disproportionately high for atypical pathogen category

›Does not reliably distinguish from bacterial pneumonia

›D-dimer

›Independent predictor of severe disease

›AUC 0.765 for severity prediction

›Elevated due to systemic inflammation and coagulopathy

›High D-dimer requires assessment for concurrent PE

Organ function and metabolic profile

›Liver function panel

›AST and ALT elevated in majority of cases

›Hepatic dysfunction in up to 87.5%

›Transaminase rise is an expected finding not a contraindication

›Hypoalbuminemia common

›Low albumin associated with severe disease

›Nutritional support required in ICU patients

›Renal function

›BUN and creatinine

›AKI in 34% of psittacosis vs 12% in typical CAP

›BUN-to-albumin ratio: AUC 0.88 for predicting AKI

›Urinalysis for proteinuria and casts

›Electrolytes

›Hyponatremia in > 50% of cases

›SIADH pattern possible

›Monitor closely in elderly patients

›Hypokalemia and hypocalcemia reported

›LDH

›Elevated in > 70% of cases

›Marker of tissue injury and severity

›Serial LDH tracks disease trajectory

›CK and troponin

›Elevated CK indicates myositis and severity

›Elevated troponin indicates myocardial injury

›Myocardial injury OR 124.3 for severe disease outcome

›Coagulation panel

›PT/INR, APTT, fibrinogen, D-dimer

›Prolonged PT and elevated fibrinogen in severe cases

›Disseminated intravascular coagulation in fulminant disease

›Coagulopathy guides FFP and heparin decisions

Microbiologic testing

›Metagenomic next-generation sequencing (mNGS) of BAL

›Emerging diagnostic standard for definitive identification

›Results in 48-72 hours

›High sensitivity in lower respiratory specimens

›BAL obtained via bronchoscopy preferred

›Shows hyperemia and mucosal edema on bronchoscopic evaluation

›Bronchial washings superior to sputum

›Real-time PCR for C. psittaci

›Lower respiratory specimens far superior to NP swabs

›Sensitivity 59% sputum/BAL vs 7% NP swab

›Request specifically as not included in standard respiratory panels

›Stool PCR may have diagnostic utility

›4 of 5 positive in one outbreak investigation

›Serology

›Complement fixation or microimmunofluorescence (MIF)

›Requires paired sera: acute and convalescent 2-4 weeks apart

›Four-fold rise in titer is diagnostic

›Single IgM has poor sensitivity

›Negative acute serology does not exclude psittacosis

›Most useful for retrospective or epidemiologic confirmation

›Blood cultures

›Low yield for C. psittaci (obligate intracellular)

›Required to exclude bacteremic bacterial co-pathogens

›2 sets before antibiotic initiation in septic patients

›Standard respiratory panel and urinary antigens

›Legionella urinary antigen: excludes Legionella (detects serogroup 1)

›Pneumococcal urinary antigen

›Multiplex respiratory viral panel including influenza and COVID-19

06Diagnostic Tests/dt95

Scoring Systems

›CAP severity scoring

›CURB-65 for admission decision

›Confusion: 1 point

›Urea > 7 mmol/l: 1 point

›RR >= 30: 1 point

›BP systolic < 90 or diastolic <= 60 mmHg: 1 point

›Age >= 65: 1 point

›Score interpretation

›0-1: low severity, outpatient consideration

›2: moderate severity, consider admission

›>= 3: high severity, hospital admission; consider ICU for >= 4

›PSI/PORT score as alternative stratification tool

›Class I-II: low risk, outpatient management

›Class III: moderate risk, brief observation

›Class IV-V: high risk, admission required

›IDSA/ATS major and minor criteria for severe CAP

›Major criteria: mechanical ventilation or septic shock with vasopressors

›Either major criterion indicates severe CAP requiring ICU

›Minor criteria (>= 3 of 9 = severe CAP)

›RR >= 30, PaO2/FiO2 <= 250 mmHg, multilobar infiltrates

›Confusion, BUN > 7 mmol/l, WBC < 4x10^9/L

›Platelet < 100x10^9/L, hypothermia, hypotension requiring fluids

›Psittacosis-specific severity predictors

›High-risk triad: elevated D-dimer plus lymphopenia plus elevated LDH

›AUC 0.765 for D-dimer alone

›Myocardial injury: OR 124.3 for severe disease

›Bilateral CT involvement: 76.2% vs 45.3% in non-severe

›Pleural effusion significantly more common in severe cases

MRI

›Cardiac MRI for myocarditis evaluation

›Indication: troponin elevation, ECG changes, or clinical myocarditis

›T2-weighted imaging: myocardial edema in active inflammation

›Late gadolinium enhancement: myocardial injury pattern

›Lake Louise criteria for MRI diagnosis of myocarditis

›T2 ratio > 2.0 (myocardium to skeletal muscle)

›Early gadolinium enhancement ratio > 4.0

›Late gadolinium enhancement present

›Psittacosis myocarditis is typically reversible with treatment

›Serial cardiac MRI for monitoring recovery

›Brain MRI for CNS involvement

›Indication: encephalopathy, meningismus, or focal neurologic signs

›Gadolinium-enhanced MRI preferred

›Leptomeningeal enhancement in psittacosis meningitis

›DWI sequences for stroke mimics and encephalitis pattern

›Exclude concurrent ischemic complications

CT

›CT chest for pneumonia characterization

›Primary imaging modality: superior to CXR for extent

›Consolidation in 71-100% of cases

›Ground-glass opacities: hallmark with consolidation

›Lobar distribution

›Middle and lower lobe predominance

›Air bronchograms common within consolidation

›Bilateral involvement

›Associated with severe disease

›52% in severe vs 23% in non-severe cases

›Pleural effusion

›Present in 34-79% of cases

›Significantly more common in severe disease

›Atypical patterns

›Pulmonary nodules and cavitary lesions rarely reported

›Cannot distinguish psittacosis from Legionella by CT alone

›Follow-up CT

›Resolution may take weeks to months up to 90 days

›Recommended 4-6 weeks post-discharge

›CT pulmonary angiography

›Indication: elevated D-dimer with dyspnea and no confirmed source

›Psittacosis elevates D-dimer and can mimic PE clinically

›Wells score >= 5 or PERC-positive: proceed to CT-PA

›Identifies concurrent PE in high D-dimer presentations

›CT brain

›Indication: altered mental status or focal neurologic deficit

›Excludes hemorrhage and mass lesion before LP

›May show meningeal enhancement in psittacosis meningitis

Ultrasound

›Point-of-care lung ultrasound

›B-lines pattern

›Diffuse B-lines indicate interstitial edema or ground-glass change

›Distinguishes from pneumothorax

›Consolidation

›Hepatization pattern with dynamic air bronchograms

›Real-time confirmation of lobar consolidation

›Pleural effusion

›Anechoic or complex fluid collection

›Guides thoracentesis decision and procedural planning

›Point-of-care cardiac ultrasound

›LV and RV function assessment

›Myocarditis: reduced EF, wall motion abnormalities

›Pericardial effusion in pericarditis

›Valvular vegetations in suspected endocarditis

›Limited sensitivity: TEE required if endocarditis high suspicion

›Volume status assessment

›IVC collapsibility index for fluid responsiveness

›Guides resuscitation in hemodynamically unstable patients

›Hepatic and abdominal ultrasound

›Hepatosplenomegaly confirmation

›Liver echotexture for hepatic involvement degree

›Spleen size in systemic infection assessment

07Disposition/dispo46

ICU admission criteria

›Mandatory ICU admission

›Mechanical ventilation for respiratory failure

›Intubation or high-flow nasal cannula with trajectory to intubation

›VV-ECMO for refractory hypoxemia

›Hemodynamic instability requiring vasopressors

›Norepinephrine or vasopressin requirement

›VA-ECMO for cardiogenic shock

›Multi-organ dysfunction

›AKI requiring CRRT

›Hepatic failure with coagulopathy

›High-risk triad present

›Elevated D-dimer plus lymphopenia plus elevated LDH

›Myocardial injury (troponin elevation)

Ward admission criteria

›General ward admission indications

›Hypoxia requiring supplemental O2

›SpO2 < 92% on room air

›Bilateral infiltrates on imaging

›CURB-65 >= 2 or PSI class III-IV

›Any severity predictor meeting IDSA/ATS minor criteria

›Significant organ dysfunction

›AKI without dialysis requirement

›Transaminase elevation with clinical hepatitis

›Electrolyte disturbances requiring IV correction

›Inability to tolerate oral medications

›Nausea, vomiting, or altered mental status

›Altered mental status of any degree

08Treatment/t83

Antibiotic therapy

›First-line: doxycycline

›Standard dosing

›Doxycycline 100 mg PO or IV every 12 hours

›IV formulation for severe disease or inability to tolerate oral

›Treatment duration

›Minimum 10 days for uncomplicated cases

›14-21 days for severe or complicated disease

›Extend to 21 days for endocarditis or CNS involvement

›Efficacy data

›95.7% effective rate in multicenter study

›Faster defervescence compared to fluoroquinolones

›Tetracyclines strongly preferred over fluoroquinolones as first-line

›Second-line: fluoroquinolones

›Moxifloxacin

›400 mg PO or IV once daily

›Effective but 31.0% cure rate vs 95.7% for doxycycline in one study

›Levofloxacin

›750 mg PO or IV once daily

›Alternative when moxifloxacin not available

›Use in combination with doxycycline for severe/ICU cases

›Doxycycline 100 mg IV q12h plus moxifloxacin 400 mg IV daily

›Macrolides as alternative

›Azithromycin

›500 mg PO or IV once daily for 5-7 days

›Second-line alternative for milder disease

›Preferred in pregnancy and children < 8 years

›Lower efficacy than doxycycline in direct comparisons

›Rescue therapy for refractory or severe cases

›Tigecycline

›100 mg IV loading dose then 50 mg IV every 12 hours

›Broad-spectrum glycylcycline, effective for intracellular pathogens

›Omadacycline

›300 mg IV once daily for first two doses then 300 mg IV daily

›Next-generation aminomethylcycline, case reports of success

Supportive respiratory care

›Oxygen delivery escalation pathway

›Low-flow nasal cannula: 1-6 L/min for mild hypoxia

›Step up to simple face mask 6-10 L/min if needed

›Non-rebreather mask 10-15 L/min for moderate hypoxia

›High-flow nasal cannula

›Flow 20-60 L/min, FiO2 21-100%

›ROX index monitoring for HFNC failure prediction

›ROX < 4.88 at 12 hours predicts HFNC failure

›Non-invasive ventilation (NIV/BiPAP)

›IPAP 10-20 cmH2O, EPAP 5-10 cmH2O

›Trial in cooperative patients without vomiting

›Invasive mechanical ventilation

›Lung-protective ventilation strategy

›Tidal volume 6 ml/kg predicted body weight

›Plateau pressure < 30 cmH2O

›PEEP titration

›ARDSNet low PEEP/FiO2 table as starting point

›Titrate for SpO2 88-95% and hemodynamic tolerance

›Prone positioning for PaO2/FiO2 < 150 mmHg

›16-hour prone sessions per PROSEVA protocol

›Class I recommendation for severe ARDS

Advanced organ support

›Extracorporeal membrane oxygenation

›VV-ECMO for refractory hypoxemia

›PaO2/FiO2 < 80 mmHg despite lung-protective ventilation

›Survival reported in psittacosis-associated ARDS cases

›VA-ECMO for cardiogenic shock or cardiac arrest

›Psittacosis with cardiogenic shock from myocarditis or DCM decompensation

›Case reports of successful VA-ECMO rescue in psittacosis

›Renal replacement therapy

›CRRT for AKI with fluid overload or severe metabolic derangement

›AKI in 34% of psittacosis cases

›Continuous mode preferred in hemodynamically unstable patients

›Corticosteroids

›Limited evidence; used in severe cases with refractory inflammation

›Dexamethasone 6 mg IV daily if considered

›Risk-benefit assessment; not standard of care

Medication safety notes

›Doxycycline interactions and cautions

›Avoid within 2 hours of dairy, antacids, calcium, or iron supplements

›Chelation significantly reduces absorption

›Administer on empty stomach when possible

›Photosensitivity: counsel on sun protection

›Esophageal irritation: advise adequate fluid with each dose

›Contraindications

›Doxycycline contraindicated in pregnancy

›Use azithromycin 500 mg PO daily as alternative

›Category D teratogen: affects fetal bone and tooth development

›Doxycycline caution in children < 8 years

›Risk of dental staining and bone growth effects

›Use azithromycin or consult pediatric ID

09Special Populations/sp53

Pregnancy

›Antibiotic selection in pregnancy

›Doxycycline is contraindicated in all trimesters

›Causes fetal tooth discoloration and impaired bone development

›Category D teratogen

›Azithromycin is the preferred alternative

›500 mg PO or IV daily for 7-14 days

›Crosses placenta but category B; generally considered safe

›Moxifloxacin is relatively contraindicated

›Fluoroquinolones: concern for arthropathy in developing fetus

›Use only if no alternatives and disease is life-threatening

›Disease severity considerations in pregnancy

›Psittacosis in pregnancy has historically been associated with miscarriage

›Spontaneous abortion and preterm birth reported in case series

›Placental involvement documented

›Obstetric consultation mandatory for any pregnant patient with psittacosis

›Fetal monitoring frequency determined by gestational age

›Consider inpatient monitoring for third-trimester cases

Geriatric

›Risk profile in older adults

›Age > 65 years is independent risk factor for severe disease

›Higher baseline comorbidity burden: cardiac, renal, pulmonary

›Chronic cardiac disease especially DCM increases risk of cardiogenic shock

›Atypical presentation common

›Absence of fever in up to 30% of elderly with pneumonia

›Confusion or delirium may be presenting or only symptom

›Management modifications

›Doxycycline dose adjustment not required for age alone

10Background/b80

Epidemiology

›Incidence and global burden

›Psittacosis is globally underdiagnosed

›Incidence markedly underestimated due to nonspecific presentation

›True incidence unknown; reported cases represent a fraction of actual burden

›Zoonotic disease associated with bird handling worldwide

›Sporadic cases and outbreaks reported in Europe, Asia, North America, Australia

›Nationally notifiable disease in the United States

›Seasonal pattern: peak incidence autumn to winter (September-April)

›At-risk populations

›Occupational exposure

›Poultry workers: highest occupational risk group

›Veterinarians, pet shop employees, bird breeders

›Slaughterhouse workers handling poultry

›Pet bird owners

›Psittacine birds (parrots, parakeets, cockatiels) highest risk

›Pigeons and other wild birds also reservoir hosts

›Demographics

›Male sex is independent risk factor for severe disease

›Age > 65 independent risk for severe pneumonia

›Transmission

›Inhalation of aerosolized bird droppings, feathers, secretions

›Does not require prolonged contact; brief exposure sufficient

›Dried droppings remain infectious for weeks

›Human-to-human transmission

›Rare but documented in outbreak investigations

›Swedish 2013 outbreak: 1 case transmitted to 10 contacts including HCW

›Chinese 2020 outbreak: secondary and tertiary transmission documented

Pathophysiology

›Organism characteristics

›Chlamydia psittaci: obligate intracellular gram-negative bacterium

›Cannot synthesize ATP; entirely dependent on host cell energy

›Two forms: elementary body (infectious) and reticulate body (replicative)

›Life cycle

›Elementary body inhaled and phagocytosed by alveolar macrophages

›Reticulate body replicates within membrane-bound inclusion

›Cell lysis releases elementary bodies to infect adjacent cells

›Immune evasion

›Inhibits phagosome-lysosome fusion

›Intracellular location protects from beta-lactam antibiotics

›Explains beta-lactam treatment failure

›Pulmonary and systemic injury

›Alveolar macrophage tropism leads to alveolar inflammation

›Diffuse alveolar damage in severe cases

›Cytokine storm with IL-6 and TNF-alpha elevation

›Hematogenous dissemination

›Bacteremia enables extrapulmonary involvement

›Hepatic tropism explains high rate of transaminase elevation

›Cardiac involvement mechanism

›Direct myocardial infection or immune-mediated myocarditis

›DCM decompensation triggered by systemic inflammation

›Neurologic involvement

›CNS dissemination via bacteremia

›Meningeal inflammation without purulent exudate typical

Therapeutic Considerations

›Antibiotic mechanism rationale

›Tetracyclines: mechanism of action

›Inhibit 30S ribosomal subunit; intracellular penetration essential

›Doxycycline accumulates intracellularly at high concentrations

›Superior intracellular penetration explains 95.7% cure rate

›Fluoroquinolones: mechanism of action

›Inhibit DNA gyrase and topoisomerase IV

›Good intracellular penetration but lower cure rates than doxycycline

›Macrolides: mechanism of action

›Inhibit 50S ribosomal subunit

›Intracellular accumulation but less efficacy data

›Beta-lactams are ineffective

›Target cell wall synthesis; obligate intracellular organism lacks target

›High clinical relevance: failure on beta-lactams should trigger psittacosis testing

›Duration of therapy considerations

›Minimum 10 days to prevent relapse

›Relapse documented with courses < 10 days

›Intracellular persistence requires prolonged therapy

›Extended courses for severe disease

›14-21 days for ICU-level illness

›21 days for endocarditis, CNS involvement

›Monitoring parameters

›Defervescence expected within 48-72 hours of doxycycline

›Persistent fever > 72 hours: reassess diagnosis and antibiotic choice

›Serial CRP and LDH for treatment response

›Follow-up chest imaging

›Radiographic resolution lags clinical recovery

›CT at 4-6 weeks post-discharge; full resolution may take 90 days

11Patient Discharge Instructions/pdi51

copy discharge instructions

›Diagnosis and cause

›You have been diagnosed with psittacosis (parrot fever)

›This is a lung infection caused by a bacteria from birds

›You likely caught it from contact with an infected bird or its droppings

›This infection responds well to the right antibiotics (doxycycline)

›Most people recover fully within 1-2 weeks on treatment

›Antibiotic instructions

›Take doxycycline exactly as prescribed for the full course

›Do not stop early even if you feel better

›Stopping early can cause the infection to come back

›How to take doxycycline correctly

›Take with a full glass of water

›Do not take with dairy products, antacids, calcium, or iron supplements

›Wait at least 2 hours between doxycycline and these substances

›Side effects to expect

›Nausea is common; take with food if needed

›Increased sensitivity to sunlight: wear sunscreen and protective clothing

›Heartburn or throat irritation: do not lie down for 30 minutes after taking

›Activity and recovery

›Rest and adequate hydration are essential for recovery

›Drink at least 6-8 glasses of water daily

›Avoid strenuous activity until fever-free for at least 48 hours

›Fatigue may persist for 1-2 weeks after infection resolves

›Chest X-ray or CT may not appear normal for up to 3 months

›This does not mean the infection is still active

›Bird and household precautions

›Do not resume handling birds until source is identified and treated

12References/r36

Guidelines and key sources

›Ni Y, Zhong H, Gu Y, et al. Clinical features, treatment, and outcome of psittacosis pneumonia: a multicenter study. Open Forum Infectious Diseases. 2023.

›Multicenter study on clinical features and outcomes; doxycycline 95.7% vs fluoroquinolone 31.0% cure rate

›PubMed PMID 36817742

›Li X, Xiao T, Hu P, et al. Clinical, radiological and pathological characteristics of moderate to fulminant psittacosis pneumonia. PLoS One. 2022.

›Severity predictors: bilateral CT, D-dimer, lymphopenia, LDH

›PubMed PMID 35816485

›Li J, Xue Y, Cui J, et al. Admission clinical features associated with disease severity in psittacosis pneumonia: a retrospective study. Diagnostic Microbiology and Infectious Disease. 2026.

›Myocardial injury OR 124.3 for severe disease; D-dimer AUC 0.765

›PubMed PMID 41734523

›Song Y, Li N, Ni W. Systemic inflammation, multi-organ injury, and acute kidney risk in psittacosis pneumonia. Frontiers in Cellular and Infection Microbiology. 2025.

›AKI in 34% psittacosis vs 12% typical CAP; BUN-to-albumin ratio AUC 0.88

›PubMed PMID 41878259

›Wallensten A, Fredlund H, Runehagen A. Multiple human-to-human transmission from a severe case of psittacosis, Sweden, January-February 2013. Euro Surveillance. 2014.

›Human-to-human transmission documentation; index case to 10 contacts

›PubMed PMID 25358043

›Zhang Z, Zhou H, Cao H, et al. Human-to-human transmission of Chlamydia psittaci in China, 2020. The Lancet Microbe. 2022.

›Secondary and tertiary transmission chain confirmed

›PubMed PMID 35617977

›Wu HH, Feng LF, Fang SY. Application of metagenomic next-generation sequencing in the diagnosis of severe pneumonia caused by Chlamydia psittaci. BMC Pulmonary Medicine. 2021.

›mNGS diagnostic utility; BAL superior to NP swab for PCR

›PubMed PMID 34556069

›McGovern OL, Kobayashi M, Shaw KA, et al. Use of real-time PCR for Chlamydia psittaci detection in human specimens during an outbreak of psittacosis — Georgia and Virginia, 2018. MMWR. 2021.

›PCR detection rates: 59% sputum/BAL vs 7% NP swab

›PubMed PMID 33830980

›Raven S, Heijne M, Koomen J, et al. Circulation of avian Chlamydia abortus in the Netherlands and community-acquired pneumonia: an outbreak investigation. The Lancet Infectious Diseases. 2025.

›Incubation period 7-14 days; clinical spectrum and outbreak epidemiology

›PubMed PMID 39426392

Evidence & Review

Evidence & Review