Intro to Respiratory Viruses Flashcards
What are the different forms of upper respiratory infections (URI)?
rhinitis, pharyngitis, sinusitis and laryngitis
What are the different forms of lower respiratory infections (LRI)?
bronchitis, bronchiolitis, pneumonia
What is interstitial pneumonia?
infection involving alveolar septae and lining
what is pleuritis?
disease of pleura
What viruses cause the common cold?
rhinovirus (most common, URI, >100 serotypes, provoke asthma), Coronavirus (URI), Respiratory syncytial Virus (RSV, LRI, pneumonia= infants), Adenovirus (URI & LRI), Parainfluenza (URI but LRI if severe), cold symptoms= influenza, metapneumovirus (LRI), enterovirus (summer), EBV
What are the different kinds of Parainfluenza viruses and their associated illnesses?
HPIV-1 and 2: childhood croup, more in fall; HPIV 3: usually spring and early summer, HPIV 4: less common; all= childhood croup, laryngeal-tracheal infection, URI, LRI
What type of respiratory illness does HHV6 cause?
interstitial pneumonia, roseola (human herpes virus)
Which respiratory viruses are more common January-March?
RSV, Influenza, Para Influenza
Which respiratory viruses are more common July - September?
enterovirus, adenovirus, arbovirus
How are respiratory viruses spread?
contact w/ respiratory secretions or aerosolized micro droplets, self inoculation via hands in eyes (tear duct into nasopharynx), inhalation, fomites (i.e. tissues)
What are the three typical respiratory viral families?
Orthomyxovirus, paramyxovirus, adenovirus
What are the features of the paramyxoviral family?
characteristic finding if multinucleated cells in culture, RNA, envelop, easily sterilized/disinfected, Para influenza 1-4, mumps, morbillivirus (measles), pneumovirus (RSV and metapneumovirus)
What are some important clinical features of RSV?
most common respiratory virus in children and infants, extreme pathogenic effect on respiratory epithelium, recovery longer than bacterial
What are some important clinical features of metapneumovirus?
second most common virus in children, similar to RSV, detection largely limited to molecular approaches
What are some important features of adenovirus?
1-41 serotypes, aerosol enteric/respiratory, myocarditis in children (viremia), epidemic infections in close dense populations (military base), conjunctivitis or swimmer’s eye (pee in pool)
How is influenza acquired? What does it cause?
through respiratory tract; widespread disease including fever, myalgia, and headache
What are the identifying features of orthomyxoviruses?
influenza; Hemagglutination protein (attach to cells, serotyping H Ag), Neurominidase protein (release of new viral particles from cells, RNA w/ 8 segments, facilitates rearrangement, serotyping N Ag
What are the clinical features of orthomyxoviruses?
influenza A: pandemic and seasonal, birds, humans, pigs, LRI; influenza B: seasonal, humans and seals, LRI and GI; influenza C: mild illness, URI rarely LRI, limited outbreaks
What are the replicative features of influenza?
(-) RNA, requires viral proteins w/ nuclear host proteins to produce mRNA and genome, in cytoplasm mRNA translated to produce viral proteins, assembly at plasma membrane, neurominidase required for bud separation from cell
What is the importance of influenza H and N antigens?
used to serogroup influenza A (16H and 9N), Ab made to these, basis for flu vaccines, allows binding with host cell, H- fusion of viral envelope with endosome when acidified, N allows budding out from cell.
What is antigenic drift?
RNA viruses make more mutations than DNA viruses, serogroups spread in population and have new mutations, gradually drift into new antigenic shape, now unrecognizable by immune system
Why do we have seasonal epidemics of influenza?
antigenic drift, small changes in H and N, how it eludes immune system, why we vaccinate yearly and vaccine updated for predicted changes
What impact does seasonal influenza have in US?
> 36K deaths (85% over 65) and 200K hospitalizations, 5-20% attack rate in gen pop and ~60% in nursing home, 10 bil. in lost productivity and medical cost
What is antigenic shift?
wild birds have different type of influenza A than humans, pig infected with human and bird virus (in same cell), virus segments combine creating new serotype which infects people who lack immunity
What caused H1N1 virus of 2009?
antigenic drift and shift
What typically causes pandemic influenza A? What is the recipe for a pandemic?
antigenic shifted virus entering human population; novel virus (pop little or no immunity), capable of replication in humans, pathogenic and virulent in humans, and capable of human-human transmission
Which viruses are being watched for the next pandemic? Why?
H5N1 and H7N9; rapid mutation, tendency to acquire genes from viruses infecting other animals, cause severe disease in birds and humans, birds that survive shed virus in feces for weeks, ~70% fatal in humans (minimal person to person spread, not well adapted yet)
what are key features of bird influenza?
not commonly transmitted between humans, high morbidity and mortality for humans
What were the notable influenza pandemics of the 20th century?
1918 Spanish flu (H1N1) ~20-40mil deaths (675K in US); Asian flu (H2N2) ~ 1-4 mil deaths (70K US); and Hong Kong Flu (H3N2) deaths 1-4 mil (34K US)
why does influenza spread so quickly?
incubation: 2 days (1-4), viral shedding: begin 1 day before onset of symptoms, peak shedding first 3 days (correlates w/ fever), subsides by 5-7 days but up to 10+ in kids
How can flu droplet spread be minimized?
limited study but: masks and respirators (N95), contact, droplet and droplet nuclei (airborne) can all occur, droplet most important (cover cough, sneeze, talk- increase coail distance, can be on surfaces)
What determines vaccine for the year?
WHO makes recommendations based on surveillance data
What is the site of action of antivirals for influenza?
amantadine and rimantadine proton transport into endosome preventing acidification; zanamivir and oseltamivir- neurominidase
Flu Vaccine vs Antivirals?
V: best prevention, limited supply, 6-9mo to produce, manufacturing limited, efficacy dependent on prediction of strains (midseason shifts!); AViral: best at stopping spread, effective treatment/prophylaxis, valuable adjunct to vaccine, limited supply
How do we treat colds?
can’t really test to find culprit (too many options takes too long to matter), fluids and rest (no AB unless evidence of B infection)
