Respiratory viruses Flashcards
The peak incidence of viral respiratory infection is in the _____
winter months
Adenovirus infection is present ______ but cases occur periodically in _________
present throughout the year
outbreaks in institutional settings- ex military trainees
The peak incidence of enterovirus respiratory disease is in the ______
late summer/ early fall
Coronavirus, influenza virus, and SRV all peak in the _____
winter
Parainfluenza virus and rhinovirus peak in the ______+
two peaks: one in fall, one in spring
Respiratory viruses are generally poor at generating_____ so re-infections are common
immune responses
Least the 10 viruses that cause respiratory illness that were covered in this class
Influenza A, B, C Enterovirus Adenovirus Parainfluenza virus Respiratory syncytial virus Rhinovirus Coronavirus Metapneumovirus Human bocavirus WU virus
Many respiratory viruses cause similar syndromes. List some symptoms that are somewhat specific for influenza
fever, malaise, muscle aches, cough, extreme fatigue
RSV causes serious ____ respiratory tract infections in ____ (age)
lower respiratory tract infections
infants 6 mo- 1 year
hospitalization is more common in boys
How are respiratory viruses diagnosed?
Culture from throat swabs, detected by immunofluorescent within 24-48 hours.
Cytopathic effects take longer to detect and may or may not be distinctive
PCR tests are available
What respiratory viruses have antivirals that can be used for treatment
influenza
RSV
ie distinguishing between rhinovirus and coronavirus is not clinically useful
What causes symptoms of the common cold?
replication of virus in the epithelial lining of the URT
irritation of nerve endings–> cough
histamines/ bradykinin–> mucus, congestion
viral replication results in killing of epithelial cells in some cases, ciliary action is often paralyzed
Describe the pathogenesis of LRT symptoms in viral infection
sloughing of dead cells blocks airways and results in dyspnea (more severe in infants)
chemotactic factors for eosinophils can exacerbate asthma/ COPD
fever from IL-1 or IFN
What is the cause of the muscle aches and malaise seen in influenza infection?
High systemic levels of IFN
What is the pathology of SARSCoV?
diffuse alveolar damage, desquamation, hyaline membranes, alveolar edema,
inflammation, syncytia formation, and thickened alveolar walls
List recommended therapies for respiratory viral illness
hydration
chicken soup-antihistamine activity
Describe how to help counsel patients about appropriate use of OTC agents for respiratory viral illness
OTCs: antihistamines, decongestants, expectorants, cough suppressants, pain relievers
recommend patients purchase drugs specific to their symptoms rather than formulated combinations (ex don’t take decongestants for influenza)
never use aspirin in kids- Reye’s syndrome
zinc- may inhibit rhinovirus proteases
What two drugs previously used to treat influenza are no longer prescribed due to high rates of resistance?
amantadine and rimantadine
What is the mechanism of action of oseltamivir and zanamivir?
neuraminidase inhibitors- block release of virus from cells, must initiate within 48 hours
What drugs can be used for respiratory syncytial virus?
aerosolized ribavirin in hospitalized infants
debate about efficacy
Palivizumab is a monoclonal antibody against RSV fusion protein, used for prevention and therapy in severe cases
** breastfeeding is protective- mom secretes anti-RSV antibodies
What is current thinking about transmission of respiratory viruses?
aerosols + many of these viruses
can survive for days on surfaces contaminated by “wet secretions”
What respiratory viruses can be prevented with a vaccine?
influenza only
failed attempts to make RSV vaccine
rhinovirus-100s of serotypes
What is the difference between the traditional influenza vaccine and FluMist?
traditional: killed vacine
FluMist: live attenuated virus, so not for use in children, elderly, pregnant, or immunocompromised
What two glycoproteins are present on the influenza virus envelope?
- hemagglutinin (H): critical for attachment and entry
- neuraminidase (N): important for viral release from cells
Describe the general pattern of influenza epidemiology over time
The pattern begins with a
pandemic. In the inter-pandemic period we see epidemics that tend to decrease in severity
followed by the outbreak of another pandemic where a large number of people are infected.
The epidemics gradually decrease in severity because the percentage of the population with antibodies against the H protein increases and thus fewer people are susceptible.
Influenza viruses that cause pandemics have been found to encode a new subtype of ____ that people have never seen before and are therefore not protected
H protein
_________ has been found to be the key factor in the ability of influenza to cause pandemics
genetic reassortment
How does genetic reassortment happen for influenza virus?
Reassortment happens when two different influenza viruses infect the same host cell. Because the genome of the virus is segmented, the newly made genome segments can be randomly packaged into
virus particles generating a reassortant virus with a new H protein
The event resulting in the generation of an influenza virus with a new H protein is known as _________
antigenic shift
The acquisition of point mutations in H and N proteins of influenza that increase the resistance of the virus to the host immune response is _________
antigenic drift
Why are viruses less able to cause severe disease after antigenic drift (vs antigenic shift)
antigenic drift does not
completely change the H or N protein, some antibody protection is retained by the host
What is the source of novel H genes?
waterfowl
What is the role of pigs in influenza epidemiology?
pigs are susceptible to infection with both human and avian strains of influenza
virus- if they are co-infected with multiple strains, they serve as mixing vessels for generation of reassorted viruses
What was significant about the 1998 outbreak of influenza in Hong Kong?
Direct transmission of influenza from birds to humans
NO human to human transmission, only affected people who directly handled birds
Since influenza can undergo _____ and ____, the protection provided by immunization is short lived and a new vaccine is needed every year
shift and drift
Describe the classic presentation of influenza
fever, headache, myalgia, fatigue, dry cough, sore throat, nasal congestion
not common: rhinorrhea, GI symptoms
systemic symptoms for 3-5 days, respiratory symptoms for an additional 4 days
What groups are at greatest risk of developing viral pneumonia from influenza?
young children, elderly, pregnant women, chronic lung or CV disease
What bacteria most typically cause secondary pneumonia following influenza infection?
S pneumoniae, S aureus, H influenzae
How does co-infection with bacteria enhance viral infection?
Proteases secreted by bacteria enhance cleavage of hemagglutinin
RSV most classically causes disease in young children but is increasingly significant in :
adults over 65, people with COPD
Describe the progression of symptoms in RSV infection
Starts with nasal congestion, pharyngitis, fever
followed by dyspnea, wheezing
Chest X ray shows interstitial infiltrates and hyperinflation of the lungs
can cause otitis media, sinusitis, can lead to secondary bacterial infections
What is the typical presentation of parainfluenza virus?
common cold with bronchitis
fever
rarely pneumonia, bronchiolitis
CROUP
What types of infections can be caused by adenoviruses?
respiratory, GI, ocular depending on subtype
Where are the sites of latency for adenovirus?
adenoids, tonsils
True or false: Even though the respiratory types of adenovirus don’t cause GI symptoms, they can be shed in the stool so in addition to spread via wet secretions, oral-fecal transmission may be possible.
true!!
What are the major symptoms of adenovirus infection?
infants: cough, pharyngitis
children: pharyngitis, tracheitis
teens: severe acute respiratory disease wiht cough, fever, sore throat, runny nose
adults: cold
immunocompromised: pneumonia, cystitis, CNS infection
some subtypes: ocular–> keratoconjunctivitis; hemorrhagic cystitis
_____ are the most common respiratory viral pathogen
rhinovirus
Rhinoviruses remain primarily in the ______ and are not associated with croup, pneumonia, bronchiolitis
URT
Rhinoviruses can exacerbate ______
asthma
Coronaviruses cause common colds and are most common in ____ and ____
winter and spring
Describe the clinical syndrome of SARS
novel coronavirus that jumped from wild cats or bats to humans in China
2-7 days of mild URT “cold” that progresses to fever, rigors, cough, dyspnea, malaise, headache, hypoxia, occasionally diarrhea
often need respiratory support
______ can cause respiratory syndromes. Peak incidence is in the summer so they are referred to as “undifferentiated febrile illness” or “summer grippe”
enteroviruses
present with cough, sore throat, fever, rarely LRT symptoms like bronchitis
complication- acute myocarditis exacerbated by exercise
Describe the presentation of WU virus
recently discovered
high hospitalization rate in children
bronchiolitis, croup, pneumonia
