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Viral Infections of the Respiratory Tract

Viral Infections of the Respiratory Tract. Respiratory tract. - Major portal of entry. - Most common afflictions in humans. - Wide range of clinical manifestations: from self-limited to devastating. Children half a dozen each year, adults two or three.

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Viral Infections of the Respiratory Tract

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  1. Viral Infections of the Respiratory Tract

  2. Respiratory tract - Major portal of entry - Most common afflictions in humans - Wide range of clinical manifestations: from self-limited to devastating • Children half a dozen each year, • adults two or three. • - Most caused by viruses. Considerable impact on quality of life and productivity of society

  3. Respiratory tract - Majority are trivial colds and sore throats • Serious lower respiratory tract • infections tend to occur at the • extremes of life • Influenza virus killing the elderly and • respiratory Syncytial virus killing the • very young Altogether over 200 known viruses

  4. Respiratory tract infection High prevalence: Large number of infectious agents and serotypes Efficiency of transmission Incomplete immunity Major reservoir schoolchildren Frequency: Higher in children under 4 years It declines in teenagers Rises again in parents Lowest in the elderly

  5. Influenza A, B, C viruses Respiratory Syncytial virus Parainfluenzaviruses 1-4 Metapneumovirus Bocavirus Adenoviruses Enteroviruses Rhinoviruses Coronaviruses Respiratory viruses

  6. Characteristics of Infection • Short incubation period (2-7 days) • Large number of virions, even before symptoms • Small number necessary to infect • Epidemic outbreaks When the proportion of uninfected susceptible persons in the community falls, the epidemic burns itself out.

  7. Viral Entry • Inhaled droplets > 10 m Ø are • trapped in turbinates of the nose • Inhaled droplets 5 -10m Ø often • reach the trachea and bronchioles

  8. Clinical features • Above the epiglottis • URTI Described according to theanatomical site of maximal involvement • Below the epiglottis • LRTI

  9. Epidemiology (1) • Transmission: respiratory route • Shedding: sneezing, coughing or talking • Sneeze: • 106 droplets < 10m  evaporation  smaller- suspended in the air for several minutes • Larger droplets fall to the ground • Spreading: • Inhalation • Direct contact

  10. Epidemiology (2) *To begin an infection: Adenovirus: 7 Influenza A virus: 3 Enterovirus: 6 *Sneezing:1.940.000 viral particles • Some viruses remain infectious for • prolonged periods

  11. Mean Annual Incidence of Respiratory Illnesses per Person-Year 7 6 5 4 3 2 1 0 Females Males Mean annual illness incidence 1 1–2 3–4 5–9 10–14 15–19 20–24 25–29 30–39 40–49 50–59 60 Age group (yr)

  12. Seasonality of Respiratory Agents: Proportion Isolated in Each Calendar Month During 6 Years Jan Apr Sep Oct Nov Dec Jan Feb Mar Apr May Jun 30 25 20 15 10 5 0 RV Parainfluenza viruses Percent 30 25 20 15 10 5 0 Respiratory syncytial virus (RSV) Influenza virus Percent Jan Apr Sep Oct Nov Dec Jan Feb Mar Apr May Jun

  13. Characteristics of VRIs of Known Etiology Coryza Cough Sore throat Activity restriction 100 Headache Lower respiratory symptoms 80 60 Percent 40 20 0 Parainfluenza virus Hemolytic streptococci RV RSV Influenza A Influenza B

  14. Respiratory Viruses and Asthma • Viruses cause asthma exacerbations in adults and children • RVs cause ~60% of virus-induced exacerbations of asthma • RVs directly infect the bronchial airways • The response to viral infection is shaped by the host’s antiviral response • VRIs in early childhood may protect against the development of asthma

  15. Viruses Detected in Adult Patients Hospitalized with Asthma Influenza A Influenza B RV Adenovirus RSV Herpes 3% 3% 6.1% 27.3% 54.5% 6.1%

  16. Respiratory Infections in Infancy May Protect Against Development of Asthma • 2 episodes of “common cold” beforeage 1 yr decrease risk of asthma by age 7by ~50% • Other viral infections— eg, herpes, varicella, measles—also protective • Reported LRI with wheeze in the first 3 years of life increases risk of asthma

  17. Acute Respiratory Infections (ARIs):PrimaryCare Office Visits, Antibiotic Use, and Bacterial Prevalence in US, 1998 Office visits Antibiotic prescription Bacterial prevalence 100 25,000 80 20,000 60 15,000 Office visits (1000) Antibiotic Rx and estimatedbacterial prevalence (% of visits) 62% 76% 40 10,000 59% 70% 30% 20 5000 0 0 Sinusitis URI Otitis media Pharyngitis Bronchitis

  18. Patients who expect antibiotics receive them more often Strongest predictor of receipt of antibiotics for ARI isMD perception of patient expectation Public beliefs about antibiotic effectiveness Useful for VRI: 55% Useful for bacterial but not viral illness: 21% Use of Antibiotics: Patient Expectations, Physician Perceptions, Public Beliefs

  19. Running nose & Sneezing “Doc, make it go away quickly, some strong antibiotics will do!”

  20. Sore throat “Doc, it is so bad ….. you must give me antibiotics!”

  21. Facial pain & Congestion “Doc, give me something, my head is exploding…. I normally take antibiotics straight away!”

  22. Painful ear “Doc, she ‘s been crying all night…… you must give her antibiotics please!”

  23. Nagging Cough “Doc, my cough is killing me …. this wouldn’t have happened if you had given me antibiotics in the first place !”

  24. Summary • VRIs are the most common infectious diseases worldwide • RVs are predominant cause of VRIs in all age groups • Transmission requires relatively close contact • Family and school major sites of transmission • RV infections peak in autumn, with minor spring peaks • RVs cause AOM, sinusitis, and bronchitis in otherwise healthy people

  25. Common Viral RT Infections • Rhinitis • Sinusitis • Pharyngitis • Laryngitis • Tracheitis • Bronchitis • Bronchiolitis • Pneumonia

  26. Rhinitis • Common colds are the most prevalent entity of all respiratory infections and are the leading cause of patient visits to the physician, as well as work and school absenteeism. • Rhinitis is the most common manifestation of common cold. • Characterized by variable fever, inflammatory edema of the nasal mucosa, and an increase in mucous secretions.

  27. Rhinitis Copious watery nasal discharge, congestion, sneezing, and a mild sore throat or cough. Little or no fever 50% last longer than 1 week and 25% last up two weeks LRTI in 60% in elderly persons common in young children

  28. Rhinitis Abnormalities observed in the sinus cavity in these patients appear to result from the entrapment of secretions and resolve 2 to 3 weeks later. Acute inflammation of the mucosa may contribute to the pathogenesis of otitis and sinusitis.

  29. Causative Agents of Rhinitis • Rhinoviruses • Coronaviruses • Parainfluenza Viruses • Respiratory Syncytial Virus • Adenoviruses • Enteroviruses ( Coxsackie, ECHO) • Influenza

  30. Rhinoviruses with more than 100 serotypes are the most common pathogens, causing at least 50% of colds in adults. • Coronaviruses may be responsible for more 10-20% of cases. • Parainfluenza viruses, Respiratory Syncytial virus, Adenoviruses and Influenza viruses have all been linked to the common cold syndrome. • All of these organisms show seasonal variations in incidence. • The cause of about 30% of cold syndromes has not been determined.

  31. Rhinoviruses • Family Picornaviridae • Numerous serotypes • Optimum temperature of growth • Acid stability • Mode of transmission • Infectivity and replication - Rhinovirus (major) ICAM-1 - Rhinovirus (minor) LDL-R

  32. GenusRhinovirus Species More than 100 Responsible for about 50% of common colds • > 100 serotypes of Rhinovirus • Re-infection can occur • Infections year-round, most prevalent in fall • and spring • Incubation period about 2 days • Symptoms peak on the 2nd and 3rd days

  33. They cause the most prevalent acute respiratory illness. • Very high attack rate (>90%) • Mostly as mild common colds with rhinorrhea, nasal obstruction, fever, sore throat, cough and hoarseness lasting for a few days. • Serious lower respiratory illness is common in infants. • Secondary bacterial infection of sinuses and middle ear.

  34. Spread by contaminated hands more than respiratory droplets. • Common cold is not caused by a change in weather, loss of sleep, going outside with wet hair, or fatigue. • Risks for contracting a cold are due to exposure to the causative viruses through personal contact. • 75% of patients infected with rhinovirus will have symptoms.

  35. Pathogenesis and Pathology • The viruses appear to act through direct invasion of epithelial cells of the respiratory mucosa with destruction and sloughing of these cells and loss of ciliary activity. • There is an increase in both leukocyte infiltration and nasal secretions, including large amounts of protein and immunoglobulin, suggesting that cytokines and immune mechanisms may be responsible for some of the manifestations of the common cold. • Pathology: inflammatory changes with hyperemia, edema and inflammation of the columnar epithelial cells lining the nasopharynx followed by desquamation.

  36. Clinical Manifestations • After an incubation period of 48-72 hours, classic symptoms of nasal discharge and obstruction, sneezing, sore throat and cough occur in both adults and children. • Myalgia and headache may also be present but fever is rare. • After 2 – 3 days, nasal discharge becomes thicker, cloudy, and yellowish in color as systemic symptoms improve.

  37. Hoarseness, cough, and sore throat may last up to 7 – 10 days. • The duration of symptoms and of viral shedding varies with the pathogen and the age of the patient. • Complications are usually rare, but sinusitis and otitis media may follow.

  38. RV % positive Clinical feature First symptom (% of subjects) Sore throat 39 Stuffy nose 17 Runny nose 17 Sneezing 8 Most bothersome symptom (% of subjects) Runny nose 36 Stuffy nose 20 Sore throat 19 Malaise 10 Median duration of symptoms (days) Cold episode 11 Sleep disturbance 4 Interference with daily activities 7 Clinical Features and Duration of Illness in Adults with RV Colds

  39. RV Infection in the Elderly • In persons 60–90 years of age with RV infection, median duration of illness was16 days • 19% were confined to bed; 26% had restriction of daily activities • 63% had lower respiratory tract symptoms;43% consulted their physician • Burden of RV infection in the elderly appears to exceed that of influenza

  40. Diagnosis • Made on clinical grounds – patient symptoms, nasal examination showing reddened, edematous mucosa, narrowed nasal passages, and watery discharge • Laboratory and/or imaging only indicated if other conditions are strongly suspected • Viral isolation/culture is not practical

  41. Management/Treatment • No curative treatment • Supportive therapy – 10 treatment • Fluids, rest, humidification, and decongestants • Analgesics, cough suppressants, mucolytics, and antihistamines are also helpful • Short term use of zinc lozenges (zinc gluconate 10-15 mg q 2 hrs) has shown to reduce duration of subjective symptoms if begun early in the course of disease

  42. Inappropriate prescribing of antibiotics is common due to • Patient beliefs/misinformation of cold being bacterial in origin • Rural location • Female gender • Patients with purulent secretions • Antibiotics should be considered if symptoms last longer than 10-14 days, due to an 80% chance of a secondary infection occurring

  43. Sinusitis • Sinusitis is an extremely common part of the common cold syndrome • RVs have been detected in 50% of adult patients with sinusitis by RT-PCR of maxillary sinus brushings or nasal swabs • Frequency of association of RV infection with sinusitis suggests that common cold could be considered a rhinosinusitis

  44. Sinusitis Signs and symptoms • Patient may complain of a ‘feeling of fullness’ and pressure over the involved sinuses, nasal congestion, and purulent nasal discharge • Other associated symptoms include sore throat, malaise, low grade fever, headache, toothache, and cough >1 weeks duration • Symptoms may last 10 – 14 days

  45. Sinusitis Diagnosis • Based on clinical signs and symptoms • Physical examination may reveal patient described symptoms – palpate over sinuses, observe for structural abnormalities such a deviated nasal septum • Sinus radiographs may reveal cloudiness and air fluid levels • Limited coronal CT are more sensitive to inflammatory changes and bone destruction

  46. Sinusitis Management/Treatment • 2/3 of untreated patients will improve symptomatically within 2 weeks • Antibiotics may be appropriate in certain patients • Supportive therapy such as humidification, antihistamines, analgesics, and/or vasoconstrictors may relieve congestion and fullness • OTC decongestant sprays for use of more than 5 days duration should be discouraged

  47. Pharyngitis • Fewer than 25% of patients with a sore throat have true pharyngitis • Primarily seen in 5 – 18 year old population, it is common in adult women • Most common cause is viral; most common agent is rhinovirus; Self-limiting; usually lasts 3-4 days • Group A, beta-hemolytic streptococcus is the primary bacterial pathogen in 1/3 cases • Early detection reduces incidence of acute rheumatic fever and post streptococcal pharyngitis

  48. Pharyngitis • Sore throat is the prominent symptom • Erythema • Swelling of the affected tissues • Exudates: inflammatory cells overlaying mucous • membranes • Low-grade fever, mild general symptoms • Difficult to differentiate from streptococcal infection Caused by the same viruses that cause common cold and Adenovirus, Enteroviruses and Influenza virus.

  49. Viral Causes of Pharyngitis • Rhinoviruses • Adenoviruses • Coronaviruses • Epstein-Barr Virus • Herpes Simplex Virus • Parainfluenza Viruses • Respiratory Syncytial Virus • Influenza Viruses • Coxsackie Viruses

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