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26 Cards in this Set
- Front
- Back
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Influenza
Symptoms |
– Influenza Type A (also B and C)
• Short incubation period – Averaging 2 days • Headache • Fever • Muscle pain • Dry cough – Acute symptoms abate within a week • Cough, fatigue and generalized weakness may linger – Transmission already one day before symptoms for appr. one week |
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Influenza
Causative Agent |
– Influenza A virus
• Belong to orthomyxovirus • Single-stranded RNA genome – Genome divided into 8 segments • Spiked envelope H spike – hemagglutinin Aids in attachment N spikes – neuraminidase Aids in viral spread |
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Influenza
Pathogensis |
– Acquired through inhalation of infected
respiratory secretions – Virus attaches to host cells via hemagglutinin spikes – Mature viruses bud from host cell – Infected cells die and slough off • Destroy mucociliary escalator |
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Influenza
Epidemiology |
– Outbreaks occur in United States every year
• Associated with 10,000 to 40,000 deaths – Pandemics occur periodically • Most “famous” pandemic of 1918 – Spanned the globe in 9 months • Pandemics have higher than normal morbidity |
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Influenza
Epidemiology |
– Spread caused by major antigenic changes
• Antigenic drift – Consists of minor changes in spikes » Particularly hemagglutinin – Changes minimize effectiveness of immunity to previous strains » Ensures enough susceptible people are available for continued virus survival • Antigenic shift – Represent more dramatic changes – Virus strains are drastically antigenically different from previous strains – New virus comes from genetic re-assortment » Occurs when two different viruses infect a cell at the same time – Genetic mixing results in new virus that is often more virulent |
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Influenza
Prevention and Treatment |
– Vaccine can be 80% to 90% effective
– New vaccine required every year • Due to antigenic drift • Antiviral medications are 70% to 90% effective – Include amantidine and rimantidine • Must be taken early • Not a substitute for vaccine |
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Respiratory Syncytial Virus Infection
Symptoms |
– Incubation period 1 – 4
days – Runny nose – Cough and wheezing – Difficulty breathing – Fever • May or may not be present – Some develop dusky colored skin • Due to poor oxygenation – One of the causes of croup in older infants |
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Respiratory Syncytial Virus Infection
Causative Agent |
– Respiratory syncytial virus
(RSV) • Part of paramyxovirus family • Single-stranded RNA genome – Genome un-segmented • Enveloped – Lacks hemagglutinin and neuraminidase |
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Respiratory Syncytial Virus Infection
Pathogenesis |
– Enters body through inhalation
– Infects respiratory epithelium – Causes death and sloughing of infected cells – Bronchiolitis is common feature • Bronchioles become obstructed by sloughing cells – Responsible for wheezing – Inflammation of the alveoli may lead to secondary pneumonia |
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Respiratory Syncytial Virus Infection
Epidemiology |
– Outbreaks are common
• Generally from late fall to late spring, peaking mid-winter – Recovery produces short-lived immunity – Healthy adults and children usually suffer mild disease but readily spread virus |
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Respiratory Syncytial Virus Infection
Prevention and Treatment |
– No vaccine
– Isolation of sick individual best prevention – No effective antiviral medications |
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Hantavirus Pulmonary Syndrome
Symptoms |
-Early Symptoms
• Fever • Muscle ache – Especially in the lower found in initial outbreak • Nausea and vomiting • Diarrhea – Later symptoms • Unproductive cough • Increasing shortness of breath • Shock and death |
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Hantavirus Pulmonary Syndrome
Causative Agent |
-Hantavirus
• Includes Sin Nombre virus found in initial outbreak • Belongs to bunyavirus family • Single-stranded RNA Genome -Divided into 3 segments • Enveloped • Causes lifetime infections in the numerous rodents -without apparent disease |
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Hantavirus Pulmonary Syndrome
Pathogenesis |
– Enters body via inhalation of dust contaminated with urine, feces and saliva of infected rodents
– Virus enters circulation • Mechanism unknown • Carried throughout body – Infects cells that line capillaries – Inflammation causes capillaries to leak fluid into lungs • Causes suffocation and precipitous fall in blood pressure – Shock and death occur in over 40% of patients |
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Hantavirus Pulmonary Syndrome
Epidemiology |
– Emerging disease due to recent discovery
• Undoubtedly existed for centuries – Most cases in United States occur west of Mississippi River • Caused by Sin Nombre virus – Virus carried by deer mouse – Outbreaks correlate with increase mouse population • Over 30% of mice become carriers – Person-to-person spread RARE |
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Hantavirus Pulmonary Syndrome
Prevention and Treatment |
– Prevention is directed towards minimizing exposure
• Keep pet and human food in containers • Maximal ventilation when cleaning mouse droppings • Mop with disinfectant – Brooms and vacuums not preferable due to dust • Lethal traps and poisons to decrease rodent population – No proven antiviral treatment • Treatment limited to support care |
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Coccidiomycosis (valley fever)
Symptoms |
– Flu-like symptoms
including • Fever, cough, chest pain, loss of appetite and weight – Other less common symptoms include • Formation of tender nodules and pain in joints – Most recover spontaneously • Small percentage develop chronic disease |
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Coccidiomycosis (valley fever)
Causative Agent |
– Coccidioides immitis
• Dimorphic fungus • Mold form grows in soil – Hyphae develop barrel- shaped arthrospores » Spores become airborne |
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Coccidiomycosis (valley fever)
Pathogenesis |
– Arthrospores enter lung through inhalation
• Develop into thick-walled spores – Spores mature and rupture • Tissue injury and symptoms mostly caused by immune responses – Organism usually eliminated by host immunity – Small percentage of individuals suffer tissue necrosis – Rarely, organisms can be carried out through circulation to other parts of the body • Disseminated form occurs in immunosuppressed patients – Fatal without treatment |
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Coccidiomycosis (valley fever)
Epidemiology |
– Grows only in semi-arid climates
• Isolated to Western Hemisphere – Infections occur only in hot, dry, dusty seasons • Dust stirred up by earthquakes can lead to epidemics – Rainfall promotes growth of fungus • This produces increased numbers of spores – Infection can occur by traveling through endemic areas |
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Coccidiomycosis (valley fever)
Prevention and Treatment |
– Prevention directed to avoidance of dust endemic areas
– Watering and planting aid in dust control – Treatment of infection includes amohotericin B and fluconazole • Treatment is prolonged • Antimicrobials cause troublesome side effects – Disseminated disease can reactivate |
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Histoplasmosis
Symptoms |
– Most infections asymptomatic
– Symptomatic disease demonstrates • Fever, cough, chest pain, shortness of breath, mouth sores |
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Histoplasmosis
Causative Agent |
– Histoplasma capsulatum
• Dimorphic fungus • Prefers to grow in soils contaminated with bird and bat droppings • Yeast form grown in human macrophages • Mold form produces spores |
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Histoplasmosis
Pathogenesis |
– Infectious conidia are inhaled with dust
• Develop yeast form in lung • Granulomas form in infected lung tissue – Resemble tubercles of tuberculosis • Granuloma lesions replaced by scar tissue – Some calcify • In underlying immunodeficiency disease spreads throughout body |
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Histoplasmosis
Epidemiology |
– Disease occurs in tropical areas and temperate zones
– Cave explorers and spelunkers at highest risk – Most cases in United States occur in Mississippi and Ohio River drainage and in South Atlantic states |
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Histoplasmosis
Prevention and Treatment |
– No proven prevention other than avoiding contaminated areas
– Treatment is with ampotericin B and itraconazole used in most severe cases |
