Respiratory Viruses Flashcards
Are upper or lower respiratory tract infections more severe?
Lower, e.g. bronchiolitis or pneumonia, might result in hospitalizations
Acute respiratory tract infections mostly involve upper airways but can also involve lower respiratory tract
Why do we monitor influenza and vaccinate yearly?
Influenza has antigenic shift and drift, with genetic reshuffling where hemagglutinin and neuraminidase can exist in different combinations
Therefore we need to conduct influenza surveillance to detect the different viruses in the community to predict required vaccinations
Laboratory diagnosis method for respiratory viruses?
Multiplex PCR assays which can detect multiple different respiratory viruses
Immunofluorescence for antigen
Virus isolation and antibody detection serology for public health surveillance
Common symptoms for respiratory viruses
Often cause upper respiratory tract infection like sore throat, runny nose, laryngitis, middle ear infection
May cause pneumonia, esp with influenza, adenoviruses and SARS-CoV-2
Viral pneumonia can lead to secondary bacterial infection by Strep pneumoniae or staph aureus
What are orthomyxoviruses?
Influenza!
Influenza A or B depends on M protein
Influenza A has haemagglutinin and neuraminidase determining the subtypes (H3N1, H1N1 etc)
-ve strand RNA in 8 segments, enveloped with surface proteins H and N
What is antigenic shift?
New virus due to reassortment among the 8 gene segments esp in animal “mixing vessels”, may lead to pandemic
What is antigenic drift?
Change in antigenicity from season to season due to accumulation of RNA mutations
Symptoms of influenza?
Headache
Runny/stuffy nose
Sore throat
Aches
Fever
Muscle tiredness
Coughing
Vomiting
Pathogenesis of influenza
Direct viral cytopathic effects followed by immunopathologic effects
May cause secondary bacterial infection, primary viral pneumonia, with CNS and muscle involvement
Fever and muscle aches when mounting immune response
Pathogenesis of influenza
Direct viral cytopathic effects followed by immunopathologic effects
May cause secondary bacterial infection, primary viral pneumonia, with CNS and muscle involvement
Fever and muscle aches when mounting immune response
How are respiratory viruses transmitted?
Mostly through large droplets and fomites (contact)
How to treat influenza?
Neuraminidase inhibitors like oseltamivir
How to prevent influenza infection?
Immunization via mostly inactivated vaccine derived from egg cultures
Trivalent: 2 influenza A subtypes + 1 influenza B lineage
Quadrivalent: 2 A subtyles + 2 B lineages
Newer types of vaccines include aerosolized/cell culture-derived attenuated live vaccines with low severity and virility
What are paramyxoviruses?
-ve ss RNA, enveloped, 2 surface glycoproteins mediating cell entry (F and HN/H/G)
Includes measles, mumps, RSV, metapneumovirus, nipah virus etc
How does measles spread?
Highly contagious, respiratory droplets –> airborne spread
Symptoms of measles infection?
Cough, conjunctivitis, coryza, photophobia, respiratory tract symptoms, viremia and virus presence in respiratory tract and urine, koplik spots preceding measles rash
Rarely causes giant cell pneumonia, high mortality rate, affecting children with immunodeficiency
How to diagnose measles infection?
Measles antigen via immunofluorescence
PCR
IgM, IgG detection
How to prevent measles infection?
Immunization via measles-mumps-rubella MMR vaccine, consisting of a live attenuated virus
What are the symptoms of mumps?
Recovery of virus from mouth or urine, orchitis, parotitis, CSF presence, meningoencephalitis
How to diagnose mumps?
Mumps antigen by immunofluorescence
PCR
IgM, IgG detection
Features of coronaviruses?
+ve ss RNA, enveloped, with surface proteins (M and S)
Animal reservoirs
Causes pneumonia
SARS-CoV-2 pathogenesis?
2-14 day incubation period, mean of 3 days
S protein binds to ACE2 receptor to enter human lung, heart, kidney and intestinal cells
Virus undergoes rapid replication within target cells, inducing epithelial and endothelial dysfunction causing inflammatory response with cytokine and chemokine production
Pro-inflammatory cytokines and chemokines cause neutrophil activation, migration and cytokine storm, can lead to adverse effects
Symptoms of SARS-CoV-2 infection?
Fever, cough, GI symptoms, can be asymptomatic
Multisystem inflammatory syndrome is where activation of inflammatory response, often involving the respiratory tract, can lead to acute respiratory damage, distress, and static shock, especially in children
Deterioration of taste (dysgeusia) and loss of smell (anosmia)
Non-dehydrating diarrhoea, vomiting, abdominal pain
Acute kidney infarction more prevalent among those with baseline renal impairment
Headache, confusion, delirium, altered mental status, ataxia, seizures
Thrombocytopenia, prolonged clotting times, increased ALT, bilirubin, serum urea, creatinine, lowered albumin
How is SARS-CoV-2 transmitted?
Direct contact or respiratory droplets, or aerosols
Also can spread via oral-faecal route and fomites
How to treat SARS-CoV-2 infection?
Dexamethasone or remdesivir
