Lecture 24 Respiratory viral diseases

the types of influenza

- A causes the most serious disease - B produces occasional outbreaks but disease is mild - C rare subtype, usually mild infections, in rare cases can cause more severe symptoms. Harder to isolate so less is known about C.

the respiratory tract is one of the most common routes of infection what are things that protect it from invasion?

- Mucous and the mucociliary escalator - IFN response: Interferon to protect against virus - Secretory IgA - NK cells

Upper respiratory system diseases Common lower respiratory system diseases

- Rhinovirus - the primary causative agent of the common cold - Adenovirus - symptoms similar to a common cold but with a fever - Influenza - "the flu" (also upper) - Respiratory Syncytial virus (RSV)

influenza treatment

- Supportive care • Bed rest, fluids, treatments for symptoms (aspirin/NSAIDs, decongestants) - Antivirals • Neuraminidase inhibitors - Bind to the active site of NA, preventing escape - Zanamivir (Relenza) and Oseltamivir (Tamiflu) - Generally only recommended in high risk individuals • Inhibition of viral uncoating: amantadine, rimantadine - strains currently circulating are resistant

rhinovirus transmission and prevention

-aerosol sneezing -direct contact -cough and sneeze into your elbow -wear a mask -wash your hands

how does adenovirus spread -reservoir

-humans are the only reservoir slide 22

number 1 in top 10 causes of deaths in low income counteries in 2016

1. lower respiratory infections lifespan is significantly impacted by economics

RSV -causative agent

Enveloped, single-stranded RNA paramyxovirus • Causes cells in cultures to fuse into syncytia, giving name respiratory syncytial virus (RSV)

adenovirus respiratory tract infections sign and sumptoms

Signs and symptoms: runny nose, fever is typical (unlike common cold), sore throat, pus on pharynx and tonsils • Symptoms may be confused with those of strep throat • Lymph nodes of neck become large, tender; mild cough • Conjunctivitis and diarrhea may occur • Patients may develop severe cough and chest pain • May be confused with pneumonia • Recovery in 1 to 3 weeks

RSV treatment and prevention

Treatment and prevention: no effective antivirals • Preventing healthcare-associated RSV requires strict isolation techniques • Passive immunity via monthly injections of immune globulin or RhuMab (palivizumab) • No vaccine

respiratory viruses cause what type of infection?

acute infection Problem: acute viruses need to find a new host quickly. Solution: must be able to spread easily (large amount of secretions)

what areas of the respiratory tract are affected by the cold and the flu

cold: upper flu: both

RSV epi -season

common from late fall to late spring • Recovery yields only weak and short-lived immunity • Healthy children, adults usually have mild illness and readily spread virus

RSV pathogenesis

infects respiratory tract epithelium • Cells die and slough off; bronchiolitis is common • Bronchioles partially plugged by sloughed cells, mucus • Obstruction causes wheezing; may allow air into lungs but not out • Pneumonia often results; secondary infections common infects respiratory

respiratory syncytial virus infections -most common cause of and in what population

lower respiratory tract infections in infants and young children; elderly

andonovirus: causative agent -envelopes? DNA or RNA? persistent? resistant?

more than 50 antigenic types of adenoviruses infect humans • Non-enveloped, double-stranded DNA • Can remain infectious in environment for a long time • Resistant to destruction by detergents, alcohol solutions- Heat, chlorine, other disinfectants effective

adenovirus treatment and prevention

no specific treatment • Attenuated oral vaccine given only to military • Most patients recover on own; secondary bacterial infections may occur

rhinovirus replication cycle

slide 16

adenovirus summary

slide 23

great summary of RSV

slide 28

anatomy of the respiratory tract

slide 3

structure of the virus

slide 37

H and N in flu

slide 38

influenza life cycle

slide 39

creating a seasonal vaccine

slide 47 slide 49

mucociliary escalator

slide 5

antigenic shift

the process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains. can produce a virus unlike anything the human population has seen before

what population did influenza pandemic effect

young adults

causative agents of the cold -30-50% -20% -10%

• 30-50% various types of rhinoviruses • 20% coronaviruses • 10% RSV and parainfluenza viruses

antigenic drift

• HA and NA are the primary proteins on the outside of the virus envelope. - As a result, they are the primary antigens that will be recognized by the immune system. • RNA dependent RNA polymerases are error prone. - Hence mutations occur fairly often. - Mutations that are beneficial are selected. - Mutations result in antigenic DRIFT. slide 42

typical symptoms of flu

• Headache, fever, sore throat and muscle pain, usually peaks in half a day • Dry cough worsens over a few days • Usually mostly resolved within a week • Sometimes lingering feelings of fatigue for longer. • Secondary bacterial infections may develop.

symptoms of the common cold

• Malaise (general discomfort and fatigue) • Scratchy or mild sore throat • Runny nose, cough and sneezing.: Profuse watery secretions that thicken in a day or two. • Symptoms for days to a week.

rhinovirus pathogenesis

• Minimal direct virus-induced cell damage - Some damage to epithelial cells lysed in the upper respiratory tract • The symptoms of the illness are primarily caused by the immune response - Inflammation - Increased nasal secretions - Tissue swelling

causative agent of the influenza A

• Orthomyxovirus • Enveloped • Segmented (usually 8) negative (-) strand RNA genome • Reservoirs: ducks, geese, shorebirds, chickens, pigs and horses

pathogenesis

• Pathogenesis common to many respiratory viruses: - Epithelial barrier may be breached (some viruses kill epithelial cells) - The body's immune response makes you feel sick! 1. Inflammatory response is a build up of fluid, swollen and blocked passageways 2. Fever due to systemic immune response • Ciliated cells are destroyed causing loss of movement out of airways - This predisposes patient to bacterial superinfection

adenovirus pathogenesis

• Pathogenesis: attach to and infect epithelial cells • Avoids host defenses by delaying apoptosis, blocking interferon function, interfering with antigen presentation by MHC class I molecules • Following replication, "death protein" causes host cell lysis • Severe infections can result in extensive cell destruction

influenza prevention

• Prevention - The primary preventative measure is vaccination. • Recommended yearly vaccination • Especially important for high risk (<5, >65, pregnant women, people with various medical conditions) - Other standard protocols • Limit contact with sick people and with others when you're sick, cover your nose and mouth, WASH YOUR HANDS!!!

rhinoviruses -rhino means -enveloped or not -DNA or RNA, single stranded or double, positive or negative -reservoirs

• Rhino - nose • Picornaviruses (other members include polio, hepatitis A, coxsackie viruses) - Pico (small): Non-enveloped - RNA • ss (+) strand RNA genome • ~160 known serotypes • Reservoirs: Humans

respiratory syncytial virus signs and symptoms

• Signs and symptoms: Runny nose followed by cough, wheezing, difficulty breathing; possibly fever (incubation period 1 to 4 days) Bluish color indicates insufficient O • In healthy older children and adults, similar to bad cold • RSV causes croup; high-pitched cough and noisy inhalation from airway obstruction • Sometimes fatal for elderly with underlying diseases

how common are viral infection of the upper respiratory system

• Viral infections of upper respiratory system are common - Average person in U.S. gets two to five per year - Hundreds of kinds of viruses involved; symptoms similar - Infections usually subside without treatment or permanent damage, but can impair defenses: Allow for more serious secondary bacterial infections