Fungal & Viral Infectious Diseases Affecting the Respiratory System

Flashcards for reviewing fungal and viral infectious diseases affecting the respiratory system.

Coccidiomycosis (Valley Fever)

Pathogen: Coccidiodes immitis; Transmission: inhalation of fungal spores from soil; Signs/Symptoms: resemble pneumonia or TB, skin lesions in immunocompromised.

Coccidiomycosis (Valley Fever)

Diagnosis: presence of spherules in clinical specimens; Prevention: protective masks; Treatment: amphotericin B; Epidemiology: SW US & northern Mexico, limited distribution in S. America

Blastomycosis

Pathogen: Blastomyces dermatitidis; Transmission: inhalation of fungal spores; Signs/Symptoms: flu-like symptoms, painless lesions on face, purulent lesions on various organs, serious infection most likely in the immunocompromised

Blastomycosis

Diagnosis: presence of B. dermatitidis in clinical samples; Treatment: amphotericin B; Prevention: difficult to avoid in environment, high risk individuals should avoid disturbing soil, relapse is common in HIV-AIDS patients

Histoplasmosis

Pathogen: Histoplasma capsulatum; Transmission: inhalation of soil born fungal spores; Signs/Symptoms: 95% cases asymptomatic, dry cough, blood tinged sputum & skin lesions, chronic symptoms similar to TB; Virulence factor: uses alveolar macrophages to travel through body via CVS & lymphatics

Histoplasmosis

Susceptibility: children, AIDS patients, & anyone exposed to soil, especially rich in nitrogen from bird/bat droppings; Diagnosis: presence of budding yeast in macrophages, cannot rely on antibodies, due to high exposure & asymptomatic rates; Treatment: amphotericin B; Prevention: minimize exposure to disturbed soil

Pneumocystis Pneumonia (PCP)

Pathogen: Pneumocystis jiroveci; Transmission: respiratory droplets; Signs/Symptoms: difficulty breathing, anemia, hypoxia, fever; Prevention: difficult, many asymptomatic carriers, maintain a healthy immune system

Pneumocystis Pneumonia (PCP)

Susceptibility: highest risk in immunocompromised patients; Diagnosis: sputum samples taken for microscopic analysis & PCR test confirmation; Treatment: combination of antifungals (trimethoprim & sulfamethoxazole)

Hantavirus Pulmonary Syndrome (HPS)

Pathogen: Hantavirus strains; Transmission: inhalation or direct contact with mucous membranes after contact with infected rodent droppings/urine or saliva, bite from infected rodent

Hantavirus Pulmonary Syndrome (HPS)

Signs/Symptoms: high fever, head/body aches, malaise, dry cough, progresses to shortness or breath, pneumonia; Susceptibility: anyone exposed to rodents in endemic areas; Prevention: no vaccines available, avoid rodent droppings; Treatment: prompt supportive care (ventilator, etc.)

Respiratory Syncytial Virus (RSV)

Pathogen: respiratory syncytial virus (RSV); Transmission: via direct, close contact with infected person, not airborne; Signs/Symptoms: fever, runny nose, coughing in babies & immunocompromised individuals, mild, cold-like symptoms in others; Virulence factor: formation of syncytia allows virus to evade immune system recognition; Diagnosis: signs of respiratory distress + immunoassay

Respiratory Syncytial Virus (RSV)

Prevention: aseptic techniques, new vaccine approved in US in July 2023, reduces risk of serious disease by almost ~75%; Treatment: supportive therapy for babies, anti-RSV immunoglobulins

Rhinitis (Common cold)

Pathogens: >200 viruses – Rhinoviruses (most common) & Coronaviruses; Transmission: respiratory droplets, indirect via fomites; Diagnosis: signs/symptoms primarily, tests can only exclude other possible diseases; Prevention: hand washing, avoid touching eyes/nose, avoid contact with infected individuals, use proper cough/sneeze hygiene

Rhinitis (Common cold)

Treatment: OTC cough suppressants, NSAIDs, decongestants, antibiotics have no effect

Influenza

Family Orthomyxoviridae: Influenza virus types A, B, & C; Anatomy: variable ssRNA genome, surface glycoproteins (hemagglutinin & neuraminidase), ion channels

Influenza

Virulence factors: virus infects ciliated cells of the respiratory mucosa, mutations of glycoproteins create new strains to evade immune recognition

Antigenic drift

Mutations and recombinations in the genes coding for HA and NA spikes are responsible for the production of new strains of influenza A and B viruses.

Antigenic shift

Antigenic shift by influenza A virus occurs about once a decade. Influenza B virus does not undergo antigenic shift.

Influenza

Signs/Symptoms: sudden high fever, pharyngitis, congestion, dry cough, myalgia; Diagnosis: includes both culture & non-culture tests, rt-PCR is preferred method

Influenza

Transmission: inhalation of aerosols & droplets, indirect contact with contaminated fomites; Pathogenesis: disproportionately affects young, elderly & immunocompromised, symptoms produced by immune response, susceptible to secondary bacterial infections

Influenza

Prevention: hand washing, avoiding crowds, annual multivalent vaccine; Treatment: antivirals effective if taken early

Influenza Treatment

Drugs target both influenza types A & B: baloxavir, peramivir, zanamivir, oseltamivir; Drugs that target only type A: amantadine/rimantadine (not recommended due to resistance)

Swine Flu (H1N1)

Pathogen: novel strain of flu affecting humans; quadruple reassortant virus – shares genes with influenza flu viruses from pigs, birds & humans

Spanish Flu

1918 H1N1; Targeted healthy adults between 20 – 40 years

Novel H1N1 (Swine Flu)

Combination of genes from pig & bird viruses in U.S. & Eurasia

Coronaviruses

family of ~40 viruses in four groups: alpha, beta, delta, gamma

Severe Acute Respiratory Syndrome (SARS)

first seen in China in 2003; spread to 24 countries within months; disappeared by 2004 due to: short incubation period, obvious symptoms, effective quarantine efforts

Middle East Respiratory Syndrome (MERS)

first seen in Saudi Arabia in 2012; first cases in U.S. in 2014; Transmission: person-to-person, prolonged, close contact, contact with dromedary camels; Prevention: avoid direct contact with camels, practice good hygiene

COVID-19

first seen in Wuhan, China in 2019; suspected source: wet animal market; transmission route unknown; intermediate species may be involved

COVID-19 Origins

direct zoonotic spillover - possible-to-likely; via intermediate host - likely to very likely; via cold food chain products - possible pathway; via laboratory incident - extremely unlikely pathway

COVID-19

human outbreaks driven by person-to-person contact; some confirmed cases of human to animal transmission