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H7N9 Influenza
Cardiovascular Presentations
Abdominal aortic aneurysm
Acute coronary syndrome (NSTEMI)
Acute coronary syndrome (STEMI)
Acute decompensated heart failure
Acute limb ischemia
Acute mesenteric ischemia
Aortic dissection
Aortic stenosis
Atrial fibrillation and flutter
Bradyarrhythmia and heart block
Cardiac arrest
Deep vein thrombosis
Myocarditis
Pericarditis
Pulmonary embolism
Stable angina
Superficial thrombophlebitis
Superior vena cava syndrome
Supraventricular tachycardia
Syncope (cardiogenic)
Unstable angina
Ventricular tachycardia
Respiratory Presentations
Acute bronchitis
Acute respiratory failure
Aspiration pneumonia
Asthma exacerbation
Bronchiolitis
Community-acquired pneumonia
COVID-19 pneumonia
COPD exacerbation
Croup
Croup (laryngotracheobronchitis)
Epiglottitis
Hemothorax
Hospital-acquired pneumonia
Pleural effusion
Pneumothorax (traumatic)
Pulmonary contusion
Spontaneous pneumothorax
Neurological Presentations
Bell's palsy
Benign paroxysmal positional vertigo
Brain abscess
Cauda equina syndrome
Cervical radiculopathy
Concussion (mild traumatic brain injury)
Encephalitis
Guillain-Barré syndrome
Hemorrhagic stroke (intracerebral)
Ischemic stroke
Lumbar radiculopathy
Malignant spinal cord compression
Migraine
Peripheral neuropathy (acute)
Retropharyngeal abscess
Schizophrenia (acute exacerbation)
Seizure (breakthrough:known epilepsy)
Seizure (first-time)
Spinal cord injury
Status epilepticus
Subarachnoid hemorrhage
Tension headache
Transient ischemic attack
Traumatic brain injury (moderate-severe)
Vestibular neuritis
Viral meningitis
Gastrointestinal Presentations
Acute appendicitis
Acute cholecystitis
Acute diverticulitis
Acute pancreatitis
Anal fissure
Choledocholithiasis and cholangitis
Clostridioides difficile colitis
Gastritis
Gastroenteritis (viral and bacterial)
Gastroesophageal reflux disease
Incarcerated or strangulated hernia
Inflammatory bowel disease flare
Large bowel obstruction
Lower GI hemorrhage
Peptic ulcer disease
Perforated viscus
Small bowel obstruction
Upper GI hemorrhage
Genitourinary and Reproductive Presentations
Acute prostatitis
Acute urinary retention
Ectopic pregnancy
Epididymitis
Orchitis
Ovarian torsion
Paraphimosis
Pelvic inflammatory disease
Priapism
Pyelonephritis
Renal laceration
Ruptured ovarian cyst
Testicular torsion
Tubo-ovarian abscess
Urinary tract infection (uncomplicated)
Urolithiasis (renal colic)
Vaginal bleeding (non-pregnant)
Infectious Disease Presentations
Acute sinusitis
Acute tonsillitis
Acute upper respiratory infection
Animal bite
Bacterial meningitis
Cellulitis
Conjunctivitis (bacterial)
Dental abscess
Endocarditis
Febrile neutropenia
Fournier gangrene
Hand-foot-mouth disease
Hepatitis (acute)
Herpes zoster
HIV-related illness
Human bite
Impetigo
Infected diabetic foot ulcer
Infectious mononucleosis
Influenza
Necrotizing fasciitis
Osteomyelitis
Otitis externa
Parasitic infection
Periorbital cellulitis
Peritonsillar abscess
Scabies
Sepsis
Septic arthritis
Spontaneous bacterial peritonitis
Tick-borne illness (Lyme disease)
Tinea infection
Tuberculosis
Viral exanthem
Wound infection
Trauma Presentations
Achilles tendon rupture
ACL and mceniscus tear
Ankle fracture
Ankle sprain
Burn
Calcaneus fracture
Cervical spine fracture
Clavicle fracture
Dental avulsion
Distal radius fracture
Drowning
Elbow fracture and dislocation
Electrical injury
Facial bone fracture
Facial laceration
Femur fracture
Fingertip amputation
Forearm fracture (radius and ulna)
Frostbite
Hand:finger laceration
Heat exhaustion
Heat stroke
Hip fracture
Humeral shaft fracture
Knee dislocation
Knee sprain
Lightning injury
Mandible fracture
Metacarpal fracture
Metatarsal fracture
Muscle strain
Nasal fracture
Non-accidental trauma
Orbital fracture
Patella fracture
Phalanx fracture (finger)
Proximal humerus fracture
Pulmonary contusion
Rib fracture
Rotator cuff tear (acute traumatic)
Scalp laceration
Scaphoid fracture
Shoulder dislocation
Skull fracture
Splenic laceration
Sternal fracture
Supracondylar pediatric fracture
Tendon laceration (hand:wrist)
Thoracic and lumbar spine fracture
Tibia:fibula fracture
Tibial plateau fracture
Toe fracture
Traumatic epistaxis
Traumatic hyphema
Toxicologic Presentations
Acetaminophen toxicity
Alcohol intoxication
Alcohol withdrawal
Anticholinergic toxicity
Anticoagulant overdose
Benzodiazepine overdose
Benzodiazepine:sedative overdose
Beta-blocker and calcium channel blocker toxicity
Carbon monoxide poisoning
Caustic ingestion
Digoxin toxicity
Drug eruption
Foreign body ingestion
Opioid intoxication
Opioid overdose
Opioid withdrawal
Organophosphate
Salicylate toxicity
Serotonin syndrome
Stimulant intoxication (cocaine, methamphetamine)
Tricyclic antidepressant overdose
Psychiatric Presentations
Acute anxiety
Acute psychosis
Agitation:behavioral emergency
Bipolar disorder
Conversion disorder
Major depressive episode
Neuroleptic malignant syndrome
Suicidal ideation and attempt
Musculoskeletal and Rheumatologic Presentations
Acute low back pain (mechanical)
Bursitis
Cervical radiculopathy
Costochondritis
Gout (acute)
Lumbar radiculopathy
Pseudogout
Tendinitis
Dermatology Presentations
Acute eczema (Eczema acute flare)
Allergic contact dermatitis
Erythema multiforme
Henoch-Schönlein purpura
Pressure injury
Psoriasis (acute flare)
Stevens-Johnson syndrome
Toxic epidermal necrolysis
Urticaria (acute)
Environmental and Exposure Presentations
Envenomation (snake, spider, insect)
High-altitude illness
Hypothermia
Hematologic and Oncologic Presentations
Acute chest syndrome
Coagulopathy
Hyperviscosity syndrome
Sickle cell crisis (vaso-occlusive)
Symptomatic anemia
Thrombocytopenia (severe)
Tumor lysis syndrome
Pediatric-Specific Presentations
Bronchiolitis
Croup
Emergency delivery
Febrile seizure
Kawasaki disease
Neonatal jaundice
Neonatal sepsis
Nursemaid's elbow
Pediatric fever 0 to 28 days
Pediatric fever 29 to 60 days
Pediatric fever 61 to 90 days
Pyloric stenosis
Slipped capital femoral epiphysis
Intussusception
Endocrine and Metabolic Presentations
Adrenal crisis
Diabetic ketoacidosis
Hypercalcemia
Hyperosmolar hyperglycemic state
Hypertensive emergency
Hypertensive urgency
Hypoglycemia
Myasthenia gravis crisis
Myxedema coma
Severe hyperkalemia
Severe hyponatremia
Thyroid storm
ENT and Maxillofacial Presentations
Acute laryngitis
Acute otitis media
Acute pharyngitis
Cerumen impaction
Epistaxis (anterior)
Nasal foreign body
Otitis externa
Tympanic membrane perforation
Ophthalmologic Presentations
Acute angle-closure glaucoma
Central retinal artery occlusion
Chemical eye injury
Corneal abrasion
Corneal ulcer
Globe rupture
Ocular foreign body
Orbital cellulitis
Retinal detachment
Obstetric Presentations
Hyperemesis gravidarum
Painful vaginal bleeding in pregnancy
Placenta previa
Placental abruption
Preeclampsia:eclampsia
Preterm labor
Threatened:inevitable:incomplete abortion
Systemic and Miscellaneous Presentations
Anaphylaxis
Angioedema
Cannabis-induced hyperemesis
H7N9 Influenza
POCUS
Procedures
Calculators
Resuscitation
ECG Guide
Back
Clinical Assessment Checklist
Browse categories and answer follow-up questions to refine your symptom profile.
Approach to the Critical Patient
Immediate priorities
Airway and breathing threats
▶
Rapidly progressive hypoxemia
▶
SpO2 often below 93% on room air at presentation
Mean onset-to-respiratory failure approximately 9 days
ARDS development
▶
Occurs in 83 to 90% of hospitalized patients
Bilateral ground-glass opacities with rapid multilobar progression
Intubation indications
▶
Inability to maintain SpO2 despite HFNC
Refractory hypoxemia not responding to NIV
If intubated, lung-protective ventilation immediately
▶
Tidal volume 6 mL per kg IBW
Plateau pressure target below 30 cmH2O
Circulation and sepsis threats
▶
Septic shock pattern
▶
SBP below 90 mmHg
MAP below 65 mmHg
Multiorgan dysfunction
▶
Acute kidney injury monitoring
Rhabdomyolysis with elevated creatine kinase
DIC with coagulation derangement
If septic shock, vasopressors and ICU escalation
▶
Norepinephrine first-line vasopressor
Broad-spectrum antibiotics for bacterial co-infection
Isolation and public health
▶
Airborne plus contact plus standard precautions immediately
▶
Negative pressure room if available
N95 respirator for all healthcare workers
Immediate public health notification upon clinical suspicion
▶
Testing coordinated through state health department and CDC
Contact tracing of close contacts
Monitoring and targets
Respiratory monitoring
▶
Continuous pulse oximetry
▶
SpO2 target 92 to 96%
Escalate supplemental oxygen early
Serial chest imaging
▶
Rapid progression expected within 1 to 2 weeks
CT preferred over CXR for detailed assessment
Arterial blood gas for ventilated patients
▶
PaO2 and PaCO2 mmHg tracking
pH monitoring for worsening acidosis
Escalation triggers
▶
Rising oxygen requirement despite HFNC
▶
Early intubation planning
ECMO consideration for refractory hypoxemia
Hemodynamic deterioration
▶
Vasopressor initiation
ICU level care
Neuropsychiatric deterioration
▶
Altered mental status in up to 33% of cases
Rule out secondary bacterial meningitis
Antiviral initiation
Empiric antiviral therapy
▶
Oseltamivir first-line
▶
Standard 75 mg PO twice daily
Critically ill 150 mg PO twice daily
Do not wait for confirmatory RT-PCR
Peramivir if oral route unavailable
▶
600 mg IV daily
Continue until clinical improvement
Early treatment associated with lower mortality
▶
Benefit greatest when initiated within 48 hours of onset
Benefit may extend up to 5 days post-onset
History
Exposure history
Poultry contact
▶
Live poultry market visit within prior 10 days
▶
Adjusted OR 3.4 for live market exposure
Direct poultry handling
▶
Matched OR 7.8 for direct poultry contact
Occupational poultry work
▶
Market vendor or farm worker
Travel history
▶
Travel to mainland China within prior 10 days
▶
All five epidemics confined to China 2013 to 2017
Endemic area residence
▶
Urban live bird markets as primary exposure site
Human contact
▶
Ill household members with similar illness
▶
Four family clusters with possible limited human-to-human transmission
Healthcare exposure to confirmed H7N9 patients
Symptom onset and progression
Classic presentation
▶
High fever onset
▶
Often above 39 degrees Celsius
Universal in hospitalized cases
Cough initially dry then productive
▶
Sputum production with progression
Hemoptysis in approximately 24%
Dyspnea with rapid deterioration
▶
Median onset-to-hospitalization 4 days
Median onset-to-ARDS 7 days
Associated symptoms
▶
Constitutional
▶
Myalgia common
Fatigue and chills
Gastrointestinal
▶
Diarrhea or vomiting in approximately 13.5%
Neuropsychiatric
▶
Altered mental status reported in approximately 33% of one series
Notable absence of upper respiratory symptoms
▶
Rhinorrhea typically absent
▶
Distinguishes from seasonal influenza
Conjunctivitis absent
▶
Distinguishes from other H7 subtypes
Risk factors
Demographic risk
▶
Age
▶
Median age 61 years in confirmed cases
Fatality risk higher in patients above 60 years
aOR 1.84 for ages 60 to 74 years
aOR 2.28 for ages 75 years and above
Sex
▶
Male-to-female ratio 2.4 to 1
Comorbidities
▶
Underlying conditions in 61 to 73% of cases
▶
Hypertension
Diabetes mellitus
Cardiovascular disease
Chronic lung disease including COPD
Obesity
▶
Matched OR 4.7
COPD
▶
Matched OR 2.7
Immunosuppressive medications
▶
Matched OR 9.0
Comorbidities only independent risk factor for ARDS
▶
OR 3.42
Past medical history
Chronic conditions
▶
Chronic kidney disease
▶
Baseline renal function for antiviral dosing
Chronic lung disease
▶
Baseline oxygenation status
Immunocompromising conditions
▶
Transplant
HIV
Malignancy
Vaccination history
▶
Seasonal influenza vaccine
▶
Does not protect against H7N9
No currently approved H7N9 human vaccine
Physical Exam
Vital signs
Stability assessment
▶
Temperature
▶
High fever above 39 degrees Celsius typical
Hypothermia as severe sepsis marker
Respiratory rate
▶
Tachypnea common at presentation
Rising trend as marker of fatigue
Blood pressure
▶
Hypotension in septic shock
MAP below 65 mmHg as resuscitation trigger
Oxygen saturation
▶
SpO2 often below 93% on room air
Ambulatory desaturation assessment
Respiratory exam
Lung findings
▶
Bilateral crackles and rales
▶
Diffuse rather than focal distribution
Correlates with bilateral ground-glass opacities
Decreased breath sounds
▶
Consolidation pattern
Pleural effusion in approximately 50%
Respiratory distress signs
▶
Accessory muscle use
Nasal flaring
Inability to speak full sentences
Upper airway exam
▶
Notably absent upper airway findings
▶
No pharyngeal erythema
No rhinorrhea
Absence supports H7N9 over seasonal influenza
General and systemic exam
General appearance
▶
Toxic and diaphoretic
▶
Cyanosis in severe hypoxemia
Jaundice if hepatic involvement
Mental status
▶
Altered consciousness as severity marker
New delirium
Multiorgan signs
▶
Renal
▶
Oliguria or anuria
Acute kidney injury
Cardiac
▶
Tachycardia
Signs of left ventricular failure in up to 33%
Musculoskeletal
▶
Myalgia on palpation
Rhabdomyolysis assessment
PITFALLS
Diagnostic pitfalls
▶
Standard influenza rapid antigen tests negative
▶
Specific H7N9 RT-PCR required
Routine influenza PCR panels will not detect H7N9
Antibiotic failure misinterpreted
▶
Rapidly progressive bilateral pneumonia not responding to antibiotics should raise immediate H7N9 suspicion
Absence of upper respiratory symptoms
▶
Do not rule out influenza based on absent rhinorrhea
Differential Diagnosis
Life-threatening diagnoses
Pandemic and avian influenza
▶
Avian influenza A H5N1
▶
Similar severity but younger median age 29 years versus 61
ICD-10 J09.X2
Longer onset-to-hospitalization than H7N9
H7N9 avian influenza
▶
ICD-10 J09.X2
Poultry exposure in China within prior 10 days
Other severe respiratory infections
▶
SARS-CoV-2 and COVID-19
▶
ICD-10 U07.1
Overlapping bilateral GGO pattern
Distinguish by exposure history and PCR
MERS-CoV
▶
ICD-10 J06.9
Travel to Middle East and camel exposure
Hantavirus pulmonary syndrome
▶
Rodent exposure history
North American distribution
Common mimics
Community-acquired pneumonia
▶
Bacterial CAP
▶
ICD-10 J18.9
Responds to antibiotics
Lobar rather than bilateral multilobar pattern
Legionella pneumonia
▶
Hyponatremia and diarrhea overlap
Urinary antigen positive
Streptococcus pneumoniae
▶
Lobar consolidation
Bacteremia in severe cases
Viral pneumonias
▶
RSV lower respiratory infection
▶
More common in immunocompromised and elderly
Adenovirus pneumonia
▶
Military populations at risk
Influenza A or B seasonal
▶
Upper respiratory symptoms more prominent
Responds to standard antiviral dosing
Immunocompromised patterns
▶
Pneumocystis jirovecii pneumonia
▶
ICD-10 B59
Bilateral GGOs in immunocompromised
LDH elevation
Invasive fungal pneumonia
▶
Aspergillosis in neutropenic patients
Laboratory Tests
Core infection labs
Complete blood count
▶
Lymphocytopenia
▶
Present in 88.3% of confirmed cases
Characteristic finding
Thrombocytopenia
▶
Present in 73.0% of confirmed cases
Leukopenia or normal white cell count
▶
High WBC unusual and suggests bacterial co-infection
Inflammatory markers
▶
C-reactive protein
▶
Markedly elevated in most cases
Limited specificity
Procalcitonin
▶
Elevated
May help identify bacterial co-infection
Organ function and injury markers
Hepatic panel
▶
AST elevation
▶
Nearly universal
Marker of multiorgan involvement
LDH elevation
▶
Nearly universal
Correlates with disease severity
Creatine kinase
▶
Elevated CK
▶
Myositis and rhabdomyolysis
Monitor for acute kidney injury consequence
Myoglobin if rhabdomyolysis suspected
▶
Renal injury threshold assessment
Renal function
▶
Creatinine and BUN
▶
Acute kidney injury monitoring
Antiviral dosing adjustment
Electrolytes
▶
Hyponatremia assessment
Potassium for arrhythmia risk
Coagulation studies
▶
PT and aPTT
▶
DIC evaluation
D-dimer
▶
Fibrinolysis marker in DIC
Fibrinogen
▶
Consumption in DIC
Cytokine and perfusion labs
Cytokine panel if available
▶
IL-6 markedly elevated
▶
Correlates with severity
IL-10 markedly elevated
▶
Pro-inflammatory cytokine storm marker
Lactate
▶
Above 2 mmol/l as organ hypoperfusion marker
▶
Repeat within 2 to 4 hours if elevated
Lactate clearance as resuscitation target
Blood cultures
▶
Prior to antibiotics when feasible
▶
Secondary bacterial infection in 66.7% of ICU cases
Klebsiella, MRSA, Acinetobacter reported
Microbiologic testing
H7N9-specific RT-PCR
▶
Respiratory specimen selection
▶
Nasopharyngeal aspirate preferred over NP swab alone
Sputum and tracheal aspirate high yield
Standard influenza rapid antigen tests negative for H7N9
▶
Specific H7N9 RT-PCR required for diagnosis
Median time to negative PCR from illness onset 11 days
▶
From antiviral initiation to negative PCR 6 days
Additional virology
▶
Viral culture
▶
Confirmatory but slower
35% of cases confirmed by culture
Serology
▶
Hemagglutinin inhibition assay
Useful for retrospective confirmation
Diagnostic Tests
Scoring Systems
Severity scoring tools
▶
APACHE II
▶
Used in published H7N9 case series
Higher scores predict ICU need and mortality
qSOFA
▶
RR above 22 per minute
SBP at or below 100 mmHg
Altered mental status
Screening tool for sepsis identification
SOFA score
▶
Full organ dysfunction assessment
Tracks multiorgan failure progression
Score limitations
▶
No H7N9-specific validated severity score exists
▶
Clinical trajectory and imaging progression guide decisions
All confirmed cases with pneumonia require hospitalization
▶
Scoring used for ICU triage not admission decision
MRI
MRI chest role
▶
Limited utility in acute H7N9
▶
CT preferred given superior resolution and speed
Availability and patient stability constraints
Problem-solving indications
▶
Suspected cardiac involvement
Myocarditis characterization
Contraindications
▶
Unstable ventilated patients
Non-compatible devices or implants
CT
CT chest indications
▶
Standard of care over CXR for detailed assessment
▶
Superior delineation of extent and pattern
Early findings may precede CXR changes
Diagnostic CT findings
▶
Ground-glass opacities universal finding
Consolidation with air bronchograms multilobar bilateral
Interlobular septal thickening
Right lower lobe predominance early with rapid bilateral spread
Additional CT findings
▶
Pleural effusion in approximately 50%
Centrilobular nodules
Reticular opacities
Complication findings
▶
Pneumomediastinum
Pneumothorax
Subcutaneous emphysema
Temporal CT patterns
▶
Progression within 1 to 2 weeks
▶
Rapid bilateral extension
Increasing consolidation
Resolution phase
▶
Slow resolution over weeks to months
Residual traction bronchiectasis
Parenchymal bands and cystic lesions
Ultrasound
Lung ultrasound
▶
Consolidation pattern
▶
Tissue-like echotexture
Dynamic air bronchograms
Pleural effusion assessment
▶
Free fluid versus complex septations
Thoracentesis guidance
B-line pattern
▶
Interstitial syndrome marker
Bilateral B-lines support diffuse alveolar damage
Cardiac and hemodynamic POCUS
▶
Left ventricular function assessment
▶
LV failure reported in 33% of one case series
Gross systolic function estimate
Shock differential
▶
Cardiogenic versus distributive pattern
Pericardial effusion screen
IVC assessment
▶
Fluid responsiveness estimation
Integrate with clinical assessment
Disposition
Admission criteria
Hospitalization required for virtually all confirmed cases
▶
99% of published case series required hospitalization
▶
Any suspected H7N9 with pneumonia or hypoxemia warrants admission
Observation warranted even in mild cases
▶
Rapid deterioration typical course
Serial imaging and repeat testing during observation
ICU indications
▶
Respiratory failure
▶
Requirement for HFNC
Intubation and mechanical ventilation
ECMO consideration for refractory hypoxemia
Hemodynamic instability
▶
Vasopressor requirement
Septic shock pattern
Multiorgan dysfunction
▶
Acute kidney injury requiring renal replacement
DIC with active bleeding
ICU required in approximately 76.6% of confirmed cases
Transfer and consultation
Mandatory specialist consultation
▶
Infectious disease
▶
Mandatory for all suspected cases
Antiviral management guidance
Pulmonary and critical care
▶
Ventilatory management
ECMO candidacy assessment
Public health authorities
▶
Local and state health department
CDC notification
Transfer considerations
▶
Transfer to ECMO-capable center if refractory hypoxemia
▶
Early consultation before clinical deterioration
Airborne isolation during transport
▶
N95 for transport personnel
Discharge criteria
Copy
Clinical improvement requirements
▶
Hemodynamic stability without vasopressors
▶
SBP above 90 mmHg sustained
Resolving hypoxemia
▶
Adequate oxygenation on low-flow supplemental oxygen or room air
Declining viral load
▶
Negative or decreasing RT-PCR results
Tolerating oral antivirals
▶
Completing antiviral course
Infection control clearance
▶
Viral shedding cessation confirmed by negative RT-PCR
▶
Patients remain in isolation until clinically improved and shedding ceased
Treatment
Infection control measures
Isolation precautions
▶
Airborne plus contact plus standard precautions
▶
Negative pressure room if available
N95 respirator for all healthcare workers entering room
Duration of isolation
▶
Until clinical improvement and confirmed cessation of viral shedding
Negative RT-PCR confirmation preferred
Antiviral therapy
Oseltamivir
▶
Standard dose
▶
75 mg PO twice daily for 5 days minimum
Extend in critically ill or immunocompromised until viral clearance
High-dose for critically ill
▶
150 mg PO twice daily
Used in published case series with severe disease
Renal dose adjustment
▶
Dose reduce for CrCl below 30 mL per minute
Resistance concern
▶
R292K neuraminidase mutation may emerge during treatment
Switch to alternative agent if clinical deterioration on therapy
Peramivir
▶
Indication
▶
Oral route unavailable
Clinical deterioration on oseltamivir
Dosing
▶
600 mg IV daily
Single dose for uncomplicated; extend in critically ill
Renal adjustment required
▶
Dose reduce for CrCl below 50 mL per minute
Zanamivir
▶
Inhaled or IV formulation
▶
Alternative when oseltamivir resistance confirmed
IV formulation available through emergency access
Inhaled dosing
▶
10 mg inhaled twice daily for 5 days
Avoid in patients with underlying airway disease
Timing principle
▶
Initiate antivirals empirically on clinical suspicion
▶
Do not wait for confirmatory RT-PCR
Early treatment within 48 hours associated with lower mortality
Benefit may extend up to 5 days post-onset
Drugs to avoid
Adamantanes contraindicated
▶
Amantadine and rimantadine
▶
H7N9 viruses universally resistant
No role in treatment or prophylaxis
Corticosteroids
▶
Avoid in H7N9 management
▶
Associated with prolonged viral shedding
Associated with worse clinical outcomes
No mortality benefit demonstrated
Salicylates
▶
Avoid in influenza illness
▶
Reye syndrome risk
Respiratory support
Supplemental oxygen
▶
Titrate to SpO2 target 92 to 96%
▶
Nasal cannula initial approach
HFNC for moderate to severe hypoxemia
NIV consideration
▶
Limited evidence in H7N9 specifically
High conversion to intubation expected
Mechanical ventilation
▶
Lung-protective ventilation strategy
▶
Tidal volume 6 mL per kg IBW
Plateau pressure below 30 cmH2O
PEEP titration for oxygenation
Prone positioning for severe ARDS
▶
PaO2 to FiO2 ratio below 150 mmHg
Minimum 16 hours per session
ECMO
▶
Consideration for refractory hypoxemia
▶
Failed conventional ventilation
PaO2 to FiO2 ratio persistently below 80 mmHg
Refer to ECMO-capable center early
▶
Before clinical deterioration precludes transport
Antibiotics for bacterial co-infection
Empiric broad-spectrum antibiotics
▶
Secondary bacterial infection in 66.7% of ICU cases
▶
Klebsiella pneumoniae
MRSA
Acinetobacter
Initial regimens used in published series
▶
Fluoroquinolones
Piperacillin-tazobactam
Carbapenems for resistant organisms
De-escalation strategy
▶
Review cultures and sensitivities at 48 to 72 hours
▶
Narrow spectrum when possible
Minimize resistance pressure
Supportive care
Fluid management
▶
Aggressive resuscitation for septic shock
▶
30 mL per kg crystalloid initial bolus
Reassess response with lactate and clinical exam
Conservative fluid strategy once stabilized
▶
ARDS fluid balance targets negative to even
Renal replacement therapy
▶
Continuous RRT for severe acute kidney injury
▶
Volume overload complicating ventilation
Uremia or electrolyte derangement
Public health management
▶
Close contact prophylaxis
▶
Oseltamivir twice-daily dosing for exposed contacts
Monitor close contacts for 7 days
Contact tracing coordination with health authorities
Special Populations
Pregnancy
Maternal risk
▶
H7N9 in pregnancy
▶
Limited published data
Physiologic changes increase respiratory compromise risk
Decreased FRC and increased oxygen consumption
Fetal monitoring
▶
Viable gestation continuous fetal monitoring
Obstetrician involvement mandatory
Antiviral safety
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Oseltamivir generally considered safe in pregnancy
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Benefits outweigh risks in severe H7N9
Standard or high dose based on severity
Avoid amantadine in pregnancy
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Teratogenicity concerns
Also ineffective for H7N9
Oxygenation targets
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Maintain SpO2 above 95% when feasible
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Fetal oxygenation depends on maternal saturation
Prone positioning considerations
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Limited in later pregnancy
Alternative positioning strategies required
Delivery considerations
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Early delivery only for fetal distress or maternal deterioration
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Airborne precautions in delivery suite
Neonatal team isolation readiness
Geriatric
Age-related risk
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Higher case-fatality ratio in older patients
▶
aOR 1.84 for ages 60 to 74 years
aOR 2.28 for ages 75 years and above
Atypical presentation possible
▶
Afebrile infection more common
Delirium as primary or early symptom
Physiologic considerations
▶
Decreased respiratory reserve
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Earlier escalation threshold for respiratory support
Renal function decline
▶
Creatinine-based oseltamivir dose adjustment
More frequent renal function monitoring
Comorbidity burden
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Polypharmacy review
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Drug interactions with antivirals
QTc prolongation risk with concurrent medications
Frailty and baseline function
▶
Goals of care discussion early in admission
ICU candidacy assessment
Pediatrics
Pediatric H7N9 presentation
▶
Milder presentation more common in children
▶
Mild upper respiratory illness without hospitalization reported
Lower case-fatality ratio than adults
Poultry exposure still primary risk
▶
Similar epidemiologic exposure requirements
Antiviral dosing
▶
Oseltamivir weight-based dosing
▶
Weight below 15 kg: 30 mg PO twice daily
Weight 15 to 23 kg: 45 mg PO twice daily
Weight 23 to 40 kg: 60 mg PO twice daily
Weight above 40 kg: adult dosing 75 mg PO twice daily
Duration minimum 5 days
▶
Extend in severe disease
Respiratory support
▶
Oxygen thresholds age-dependent
▶
Increased work of breathing triggers earlier escalation
Feeding intolerance as severity marker in infants
Lung-protective ventilation principles apply
▶
Weight-based tidal volume targets
Background
Epidemiology
Emergence and burden
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Novel reassortant avian-origin influenza A virus
▶
Emerged in China in 2013
1,568 confirmed human infections by 2019
Case-fatality ratio approximately 40%
Five epidemic waves
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2013 to 2017 in mainland China
No new human cases detected since 2019
Pandemic risk designation
▶
CDC ranks H7N9 highest potential pandemic risk of all influenza viruses
Case characteristics
▶
Median age 61 years
▶
Male-to-female ratio 2.4 to 1
ICU admission in 76.6% of confirmed cases
▶
Overall case-fatality ratio 28 to 40%
Underlying conditions in 61 to 73% of cases
Transmission epidemiology
▶
Poultry exposure primary route
▶
Live bird markets dominant exposure site
No sustained human-to-human transmission documented
Four family clusters identified
▶
Limited human-to-human transmission could not be excluded
Environmental source
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H7N9 detected in poultry, migratory birds, and live market environments
Pathophysiology
Viral characteristics
▶
Reassortant virus composition
▶
Hemagglutinin from wild aquatic bird H7 viruses
Neuraminidase from Yangtze River Delta lineage H7N9 viruses
Internal genes from H9N2 viruses
Receptor binding
▶
Dual binding to human alpha-2,6 and avian alpha-2,3 sialic acid receptors
Enables lower respiratory tract tropism in humans
Disease mechanism
▶
Predominant lower respiratory tract infection
▶
Upper respiratory tract involvement minimal
Direct viral injury to alveolar epithelium
Cytokine dysregulation
▶
Markedly elevated IL-6 and IL-10
Cytokine storm contributing to ARDS and multiorgan failure
Multiorgan failure pathway
▶
ARDS most common cause of death
Secondary bacterial infection in 66.7%
Acute kidney injury from viral and hypoperfusion injury
Rhabdomyolysis and myositis
Left ventricular failure in up to 33%
Genetic susceptibility
▶
IFITM3 rs12252-C/C genotype
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May predict severe illness
Interferon-induced transmembrane protein 3 polymorphism
Therapeutic Considerations
Neuraminidase inhibitor evidence
▶
Oseltamivir cornerstone of treatment
▶
Early treatment within 48 hours associated with lower mortality
High-dose 150 mg twice daily used in critically ill without clear mortality benefit
Resistance emergence
▶
R292K mutation conferring NAI resistance reported during treatment
Higher oseltamivir MIC in some isolates
Switch strategy required if clinical deterioration on oseltamivir
Peramivir IV alternative
▶
Useful when enteral route unavailable
Single daily dosing simpler than oral BID
Steroid avoidance rationale
▶
Prolonged viral shedding documented
▶
Worse clinical outcomes in observational data
No proven benefit for ARDS in H7N9 specifically
Contrast with other ARDS contexts
▶
General ARDS steroid evidence does not apply given viral replication concerns
Pandemic preparedness implications
▶
Pre-pandemic H7N9 vaccines developed
▶
Current H7N9 vaccines not widely distributed
Antiviral stockpiling rationale
▶
Oseltamivir and peramivir in national stockpiles
Global surveillance importance
▶
Live bird market closures in China reduced case counts
Patient Discharge Instructions
copy discharge instructions
Copy
H7N9 avian influenza recovery instructions
▶
Complete the full course of antiviral medication exactly as prescribed
▶
Oseltamivir typically 5 days minimum
Do not stop early even if feeling better
Strict respiratory hygiene
▶
Cover coughs and sneezes with elbow or tissue
Wash hands frequently with soap and water
Wear a surgical mask around household members until cleared
Avoid contact with live poultry or bird markets until fully recovered and cleared by your doctor
Do not share utensils towels or bedding with household members during recovery
Monitoring close contacts
▶
Household members and close contacts
▶
Monitor for fever or respiratory symptoms for 7 days after last exposure
Contact doctor immediately if symptoms develop
Post-exposure preventive treatment may have been prescribed
Warning signs to return to the emergency room immediately
▶
Worsening shortness of breath or difficulty breathing at rest
SpO2 below home oximeter target if provided
Coughing up blood or blood-tinged sputum
New confusion or unusual sleepiness
High fever not improving after 48 hours of antivirals
Chest pain or pressure
Decreased urination or dark urine suggesting kidney problems
Signs of severe illness including blue lips or fingertips
Expected recovery course
▶
Recovery is prolonged
▶
Weeks to months for full respiratory recovery
Residual lung scarring possible
Follow-up CT chest may be recommended by your doctor
▶
Residual changes such as scarring or bronchiectasis are common
Follow-up instructions
▶
Specialist follow-up with infectious disease as arranged
Chest clinic follow-up for pulmonary function and imaging
Contact public health as directed for close contact monitoring
References
Guidelines and key sources
CDC and public health guidance
▶
CDC Yellow Book 2025 Influenza chapter
▶
Exposure risk and post-exposure prophylaxis guidance
Oseltamivir twice-daily dosing for close contact prophylaxis
MMWR 2017 H7N9 Fifth Epidemic Update
▶
Risk factor analysis for severe disease
Age-stratified fatality risk data
Landmark clinical studies
▶
Li Q et al. NEJM 2014
▶
Epidemiology of Human Infections with Avian Influenza A H7N9 in China
Key epidemiologic and clinical characterization
Gao HN et al. NEJM 2013
▶
Clinical Findings in 111 Cases of Influenza A H7N9
Lymphocytopenia 88.3% and thrombocytopenia 73.0% data
Gao R et al. NEJM 2013
▶
Human Infection with Novel Avian-Origin Influenza A H7N9 Virus
Initial characterization of outbreak
Wang X et al. Lancet Infectious Diseases 2017
▶
Epidemiology across five epidemics 2013 to 2017
Peramivir and antiviral management data
Imaging and diagnostic references
▶
Wang Q et al. Radiology 2013
▶
Emerging H7N9 Pneumonia Radiologic Findings
Ground-glass opacity and consolidation patterns
Yu WQ et al. Internal Medicine Journal 2020
▶
H7N9 Avian Influenza Pneumonia Retrospective Analysis
Pleural effusion approximately 50% and residual fibrotic changes
Dai J et al. Chinese Medical Journal 2014
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Serial Chest Radiographic and CT Findings in H7N9
Risk factor and antiviral studies
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Liu B et al. Clinical Infectious Diseases 2014
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Risk Factors for H7N9 Disease China 2013
Poultry market OR 3.4 and comorbidity OR 3.42 for ARDS
Uyeki TM and Peiris M. Infectious Disease Clinics North America 2019
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Novel Avian Influenza Virus Infections of Humans
Comprehensive management review
Coding standards
▶
ICD-10 J09.X2 influenza due to other identified novel influenza A virus with pneumonia
SNOMED CT H7N9 avian influenza virus infection concept
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.
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H7N9 Influenza