Influenza

Description

PANCE FCM I (1. Respiratory Diseases (Infectious Disorders) Mind Map on Influenza, created by Kiley Whalen on 12/06/2021.
Kiley Whalen
Mind Map by Kiley Whalen, updated more than 1 year ago
Kiley Whalen
Created by Kiley Whalen over 3 years ago
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Resource summary

Influenza
  1. Essentials for Diagnosis
    1. Epidemic Pattern

      Annotations:

      • Epidemic pattern: annual epidemics usually appear in the fall or winter in temperate climates 
      • Influenza epidemics affect 10-20% of the global population on average each year and are typically the result of minor antigenic variations of the virus, or antigenic drift, which occur often in influenza A virus
      1. Symptoms

        Annotations:

        • Onset with fever, chills, malaise, cough, coryza, and myalgia; aching, fever, and prostrations out of proportion to catarrhal symptoms
        1. Leukopenia

          Annotations:

          • Low WBCs
        2. Pathophysiology
          1. Orthomyxovirus (RNA virus)
            1. Type A

              Annotations:

              • Infects a variety of mammals
              1. Subtypes

                Annotations:

                • Divided into subtypes based on hemagglutinin (H) and neuraminidase (N) surface expression
              2. Type B
                1. Type C
                2. Transmission

                  Annotations:

                  • Primarily droplet nuclei
                  1. Predispose pts. to secondary bacterial infections

                    Annotations:

                    • Influenza causes necrosis of the respiratory epithelium, increased adherence of bacteria to infected cells, and ciliary dysfunction, which predispose to secondary bacterial infections
                    1. Pneumococcal pneumonia

                      Annotations:

                      • most common: Pneumococcal pneumonia
                  2. Risk Factors

                    Annotations:

                    • Elderly (>65 yo), children, immunocompromised, pregnant women
                    1. Presentation/Physical Exam
                      1. Incubation Period

                        Annotations:

                        • 1-4 days
                        • In unvaccinated persons, uncomplicated influenza has an abrupt onset
                        1. Symptoms
                          1. Nearly asymptomatic
                            1. Systemic Symptoms

                              Annotations:

                              • fever (can last 1-7 days, but usually lasts around 3-5 days), chills, HA, malaise, myalgias
                              1. Respiratory Symptoms

                                Annotations:

                                • rhinorrhea, congestion, pharyngitis, hoarseness, nonproductive cough, substernal soreness
                                1. Children

                                  Annotations:

                                  • GI symptoms may be seen with influenza B
                                  1. Elderly

                                    Annotations:

                                    • May present with lassitude (ie. lethargy, fatigue) and confusion, often WITHOUT fever or respiratory symptoms
                                  2. Signs

                                    Annotations:

                                    • Mild pharyngeal injection, flushed face, conjunctival redness
                                    • Moderate enlargement of cervical lymph nodes and tracheal tenderness may be observed
                                    • The presence of fever (higher than 38.2 C) and cough during influenza season is highly predictive of influenza infection in those older than 4 years
                                  3. Diagnostics
                                    1. Rapid Tests

                                      Annotations:

                                      • Nasal and throat swabs are highly widely available, highly specific, and produce fast results—however, rapid tests have low sensitivity, leading to a high number of false-negative results
                                      1. Swabs/Cultures

                                        Annotations:

                                        • When influenza pneumonia is suspected, lower respiratory tract specimens (swabs/cultures) should be collected and tested for influenza viruses (RT-PCR commonly used)
                                        • Viral culture
                                      2. Management
                                        1. Supportive Care

                                          Annotations:

                                          • Treatment for healthy individuals is supportive
                                          1. Antivirals

                                            Annotations:

                                            • Treatment for individuals at risk for developing complications with either a suggestive clinical presentation or lab-confirmed influenza: antivirals
                                            • Maximum benefit of antivirals is expected with earliest initiation of therapy (within first 48 hours of onset of symptoms), although benefit has been noted up to 4-5 days into illness
                                            • Three neuraminidase inhibitors used for treatment of influenza A and B: oral oseltamivir, inhaled zanamivir, IV peramivir
                                            1. Oral Oseltamivir

                                              Annotations:

                                              • Drug of choice for patients of any age, pregnant women, and patients who are hospitalized or have complicated infection; dosage—75 mg twice daily for 5 days
                                              1. Inhaled Zanamivir

                                                Annotations:

                                                • Indicated for uncomplicated acute influenza in patients 7 years and older, contraindicated for individuals with asthma d/t risk of bronchospasm, lacks efficacy in presence of PNA infection; dosage—10 mg, 2 inhalations twice daily for 5 days
                                                1. IV Peramivir

                                                  Annotations:

                                                  • Used for outpatient treatment of uncomplicated infection in patients 18 years or older, recommended when there is concern about inadequate oral absorption of oseltamivir
                                                2. When To Admit

                                                  Annotations:

                                                  • -Limited availability of supporting services  - PNA or decreased O2 saturation  - Changes in mental status  - Consider with pregnancy
                                                3. Prevention

                                                  Annotations:

                                                  • Vaccines, chemoprophylaxis, hand washing and surgical masks, isolation
                                                  1. Influenza Vaccine

                                                    Annotations:

                                                    • Annual administration of influenza vaccine is the most effective measure for preventing influenza and its complications
                                                    1. Who

                                                      Annotations:

                                                      • Vaccination is emphasized for high-risk groups and their contacts and caregivers
                                                      • > 18 years, pregnant or not, can receive any of the vaccines (with few exceptions)
                                                      1. Vaccine Forms

                                                        Annotations:

                                                        • Three vaccine forms: inactivated influenza vaccines, recombinant vaccines (recombinant is only flu vaccine completely egg free, safe for those with egg allergy), and live attenuated influenza vaccine
                                                        1. Elderly Patients

                                                          Annotations:

                                                          • Elderly patients should only receive high-dose inactivated (trivalent) vaccine, usually with either hemagglutinin or an adjuvant to enhance the immune response to the vaccine
                                                          1. Precautions

                                                            Annotations:

                                                            • Take precautions if pediatric patient presents with Guillan-Barre syndrome 6 weeks after inoculation
                                                          2. Antiviral Chemoprophylaxis

                                                            Annotations:

                                                            • When an antiviral chemoprophylaxis is used, it prevents 70-90% of influenza infections
                                                            1. Not Recommended

                                                              Annotations:

                                                              • Not recommended: prior to viral exposure to prevent development of resistance, after 48 hours after exposure
                                                              1. Recommended

                                                                Annotations:

                                                                • May be recommended: patients exposed to an infected pt within two weeks of vaccination at increased risk for complications from infection, low response to vaccine d/t immunosuppression after an exposure, those with contraindication to vaccine (severe allergic rxn to flu), prevention of infection in residents of institutions during an outbreak
                                                              2. Hand Hygiene & Surgical Masks

                                                                Annotations:

                                                                • Hand hygiene and surgical masks are found to be effective in preventing the transmission of flu to un-infected individuals in the home if worn within 36 hours of onset of symptoms
                                                                1. Isolation

                                                                  Annotations:

                                                                  • Isolation (droplet) precautions should be maintained until 7 days after symptom onset or 24 hours following symptom resolution (whichever is longer)  -N95 masks should be worn for aerosol-generating procedures
                                                                2. Prognosis

                                                                  Annotations:

                                                                  • If fever recurs or persists > 4 days with productive cough and WBC count > 10,000/mcL, secondary bacterial infection should be suspected
                                                                  1. Healthy, non-elderly adults

                                                                    Annotations:

                                                                    • Healthy, nonelderly adults: duration of uncomplicated illness is 1-7 days, excellent prognosis
                                                                    1. Hospitalized Adults

                                                                      Annotations:

                                                                      • Mortality among adults hospitalized with influenza ranges from 4-8%, although higher mortality may be seen during pandemics and among immunocompromised individuals
                                                                    2. Complications
                                                                      1. Hospitalization/ICU

                                                                        Annotations:

                                                                        • Hospitalization or ICU admission for influenza is often a consequence of diffuse viral pneumonitis with severe hypoxemia and sometimes shock
                                                                        1. High Risk Groups

                                                                          Annotations:

                                                                          • Individuals with asthma, residents of nursing homes/long-term care facilities, adults aged over 65 years, morbidly obese, and persons with underlying medical conditions are at higher risk for complications
                                                                          1. Pregnancy

                                                                            Annotations:

                                                                            • Infection during pregnancy increases the risk of hospitalization, may be associated with severe illness, sepsis, PTX/ respiratory failure, spontaneous abortion, preterm labor, fetal distress
                                                                            1. Cardiovascular

                                                                              Annotations:

                                                                              • Cardiovascular diseases are a complication of influenza infection, especially among older adults (influenza is postulated to be a significant trigger for MI, cerebrovascular disease, and sudden death)
                                                                              1. Neurologic

                                                                                Annotations:

                                                                                • Neurologic complications, including seizures and encephalopathy, may occur, although more rare
                                                                                1. Reye Syndrome

                                                                                  Annotations:

                                                                                  • Reye Syndrome is a rare and severe complication of influenza (usually type B) in young children that causes rapidly progressive hepatic failure and encephalopathy—there is a 30% mortality rate; this syndrome is associated with aspirin use in the management of viral infections
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