1. Respiratory Route

• upper respiratory tract =
• nasal cavity
• pharynx
• larynx

• lower respiratory tract =
• trachea
• primary bronchi
• lungs

• hairs in nose filter out large particles
• coughing and sneezing expel particles
• lyzozyme in saliva
• mucociliary escalator
• epithelial barrier
• respiratory mucus secreted by goblet cells
• phagocytic cells (macrophages)
• local production of antibodies
• endogenous organisms - LRT is normally sterile, URT contains bacteria

goblet cells produce a layer of mucous over cilia that push particles up out of the respiratory tract

• smoking
• inhaled pollutants or dust
• impaired cough and gag reflexes
• advanced age

• mostly through respiratory route
• coughing and sneezing produce large number of droplets
• droplet infection
• close contact sometimes required
• fomites often play a role

• small-particle aerosols (droplet nuclei):
• capable of distant spread close
• contact not required
• rapid outbreak of cases

• large-particle droplet aerosols:
• close contact necessary
• spread may be slow and without clustering of cases and may go unrecognized

• fomites with self inoculation:
• direct contact with infectious secretions contaminating environmental surfaces required
• transferred from hands to mucosa
• spread among those with close and prolonged contact with infected individual and among those with poor hygiene

• rhinovirus (most common in children and adults)
• coronavirus (most common in adults)
• respiratory syncytial virus (most severe in infants)
• parainfluenza
• influenza
• adenovirus
• human metapneumovirus
• human becavirus
• occasionally bacteria

• most common cause of cold
• ssRNA virus

• aerosol
• person to person
• fomites

• viral shedding highest at beginning of symptoms
• inapparent to apparent disease ratio 3:1

• infect respiratory epithelial cells in nasal cavity
• lytic infection destroys cells
• infection and destruction of cells induces inflammation (causes symptoms)
• does not proceed lower in the respiratory tract because they are temperature sensitive
• immune response - from mucosal antibodies

• pain in nasal cavity, nasal congestion, runny nose, sneezing, sometimes cough
• accompanied by muscle aches, fatigue, headache, loss of appetite

clinical, based on signs and symptoms

only palliative not curative - anti-inflammatories or antihistamines, zinc lozenges

• wash hands
• avoid those who are sick
• vaccine difficult because so many serotypes

most caused by viruses - slower onset, less severe, clinical diagnosis, palliative treatment, avoid close contact

more severe caused by streptococcus pyogenes (strep throat)

• streptococcus pyogenes - also A beta-hemolytic streptococcus
• gram + cocci in chains
• also causes skin and tissue infections

most common cause of bacterial pharyngitis in children, one of most common bacterial infections of childhood

person to person via droplets, crowding favors spread

asymptomatic carriage may facilitate spread of disease

• adherence with pili
• M protein and carbohydrate resist initial opsonization and phagocytosis
• toxins important - streptolysins, streptococcal pyrogenic exotoxins
• immune response is effective - antibodies produced against M protein opsonize bacteria and enhance phagocytosis, neutralizing antibodies against toxins

• acute onset
• severe soreness of throat
• infected area of throat usually fiery red
• swollen lymph nodes
• fever
• can spread to middle ear and cause ear infections

• scarlet fever
• acute rheumatic fever
• rheumatic heart disease
• glomerulonephritis (kidney inflammation)

• gram stain
• hemolysis - B-hemolytic
• strep enzyme test
• lab diagnosis - crucial for accuracy

• beta-lactam antibiotics - penicillin
• immune response is sufficient, but treatment is crucial- hastens recovery, alleviates sore throat, prevents sequelae

• avoidance of close contact
• hygiene

• epstein barr virus
• dsDNA virus in herpes family

• worldwide
• in most of world children get infected at young age and rarely develop disease
• in developed countries, infection is sometimes delayed, disease more likely

respiratory route - virus in saliva, requires intimate contact

virus can be shed for months after symptoms end

• primary infection (lytic) - virus replicates in epithelial cells of pharynx, enters B cells and spreads throughout body
• persistent infection (lysogenic) - activates newly infected B cells to induce differentiation into memory cells, become latent
• immune response - both humoral and cellular, neutralizing antibodies and cytotoxic T cells against infected B cells

• sore throat, rash, lymphadenopathy, fever, extreme fatigue
• also involve in cancers
• may be involved in multiple sclerosis

• clinical
• blood work
• serological tests

• bed rest
• palliative treatment for fever, pain
• can use acyclovir steroids

avoidance, but very difficult (subclinical carriers)

• most important is streptococcus mutans
• gram+ cocci

• infants acquire organism soon after birth
• everyone has it, transmission not relevant

• plaque theory:
• bacteria form dextran from sucrose in saliva
• dextran coats teeth making surface sticky and bacteria stick to this forming plaque
• organisms become cemented to teeth at one spot
• bacteria produce acid which eats hole in tooth enamel
• immune response poor because no blood flow

• clinical based on signs
• x-rays

fillings

3 factors: susceptible teeth, bacteria, sugar

• prevention strategies:
• reduce sugar intake
• reduce bacteria and plaque by brushing, flossing, mouthwash
• increasing hardness of tooth enamel through flouridation