10-29-b- Viral Respiratory Tract Infections Part I.txt

• Respiratory infections are the #1 cause of outpatient visits in the US
• Most are just a nuisance but often can be serious or fatal (extreme cas is hantabirus pulmonary syndrome > 50% fatality
• Role of vaccines

• Upper respiratory Infections: sinusitis, common cold, pharyngitis, epiglottitis, laryngotracheitis
• Loser respiratory infections: bronchitis, bronchiolitis, pneumonia – can sometimes be fatal
• The lower you go, the more serious it gets

• Rhinoviruses
• Coronaviruses
• These two probably represent 80% or common cold infections, Rhino to Corona 4:1

Begin to have bacteria as a large number of causes as well as viruses

A lot of bacteria, viruses, as well as fungi

• Cell Killing and Immunopathology: respiratory epithelium, etc.
• Response to flu is to generate a cytokine floow, IL-1 fever

Scratchy throat, nasal discharge, malaise, headache, cough; 1-2 day incubation period, no fever

• infection of respiratory epithelium
• ciliary action stops
• mucous secretion increases
• inflammaroty reaction
• infection stopped by IFN and antibodies

• Inhalation of infected droplets
• Infected mucous transfer to nose or eye
• Children initiate outbreaks due to poor hygiene
• Fomites

• Hand washing
• Avoid people with colds
• Symptomatic

• Principal common cold virus
• Many different serotypes, makes vaccine development difficult
• But days of work lost because of symptoms
• Unenveloped; 4 structure proteins, VP1 important:
• Mimicking ICAM-1or the viral attachment site can prevent binding of virus to cell and prevent infection
• Can also target a protease that chops up the proteins into usable components that allow replication; if block protease, as in HIV as well, then block viral replication

• Resistant to drying and detergents
• Replication best at 33C
• Everyone at risk
• Worldwide, usually in winter

• Not a major cause of common colds:
• Associated with pharyngitis and a range of other diseases, including som serious lower RIs
• NOT enveloped: knobs on the virus allow interactions, many treatment prevent interactions of those knobs with the cel
• Relatively cell-independent virus, so can also target early gene production to prevent replication.

• Able to cause a wide range of disease b/c can infect many different organs, unlike rhinovirus – only respiratory tract cells
• Endemic respiratory disease:
• Acute respiratory disease of military recruits: can be fatal
• Pneumonia:
• Pharyngoconjunctival fever: eye attacked
• Keratoconjunctivitis: eye
• Less common include: gastroenteritis, pertussis-like syndrome, hepatitis, acute hemorrhagic cystitis, etc.

• Spread by: aerosol, close contact,or fecal-oral means to establish pharyngeal infection, fingers spread to eyes
• Virus infects: mucoepithelial cells in the respiratory tract, GI tract, and conjuctive or cornea, causing cell damage directly
• Virus persists: in lymphoid tissue (e.g. tonsils, adenoids, Peyer’s patches)
• Antibody – important tof prophylaxis and resolution

• Resistant to drying and GI tract (chlorine in pools)
• Asymmptomatically shed
• Day-care centers, military traning camps
• Worldwide, all seasons
• Live vaccine for military use

• Viral pharyngitis (including adeno) can resemble strep throat
• Throat swab – rapid Ag test for strep; PCR for viruses
• Adenoviruses are popular vehicles for gene therapy

• Second most common cause of colds
• Also cause GI tract infections and SARS
• Positive-stranded virus

• Infects epithelial cells of upper respiratory tract
• Enveloped virus is able to survive the GI tract
• Reinfection occurs in presens of serum antibodies

• Guangdong province, PRC, Nov 2002
• Flu-like symptoms+diarrhea
• 20% of overall fatality
• New corona virus: SARS CoV
• Source horseshoe bats (rhinolophidae species): source reservour for the virus
• Classic zoonosis

• In April 2004 when 9 people were diagnosed; linked to virology lab
• Who should be watched carefully?
• People with radiologically confirmed pneumonia, and a risk factor (visit to far east, hospital/lab contact):

• Recently-discovered paramyxovirus (2001)
• In Holland, 100% seroconversion by age 5
• Causes mild or severe URT and LRT infections in all age groups (particularly the elderly)
• Clinically similar to Respiratory Syncytial Virus (5-15 % of bronchiolitis in infants)

• 12-15% of LRT (e.g. bronchiolitis) and URT infections in children may be due to the virus
• Complicates RSV infection and found in conjunction with HIV, too. (dual infections)
• Now found worldwide
• Serious enough to warrant vaccine development