Ch 24 Flashcards
(146 cards)
1
Q
What is the structure of Paramyxoviruses ?
A
veloped, Helical nucleocapsid, negative-sense single-stranded RNA (-ssRNA)
2
Q
What are the key envelope glycoproteins and their functions Paramyxoviruses ?
A
• Fusion protein (F): Membrane fusion, syncytia formation
• Attachment proteins (HN, H, G): Receptor binding
3
Q
What are the main internal proteins in Paramyxoviruses ?
A
• N (Nucleoprotein)
• P (Phosphoprotein)
• L (Large polymerase protein)
• M (Matrix protein): Aligns nucleocapsid with envelope
4
Q
What type of diseases do Paramyxoviruses ?
A
Respiratory and systemic diseases
5
Q
In Measles & Mumps
How many serotypes and are vaccines available?
A
One serotype each; live attenuated vaccines available
6
Q
Are effective vaccines available for RSV and Parainfluenza?
A
No effective licensed vaccines
7
Q
What is the reservoir for measles virus?
A
Humans only (no animal reservoir)
8
Q
How is measles transmitted?
A
respiratory droplets, airborne spread
9
Q
How is measles transmitted?
A
Respiratory droplets and airborne spread
10
Q
What is the incubation period and when is it contagious?
A
• Incubation: 10–14 days
• Contagious: From 4 days before to 4 days after rash onset
11
Q
Where are measles outbreaks most common?
A
In unvaccinated communities
12
Q
What receptors does the measles virus use to attach to host cells?
A
• CD150 (SLAM): on immune cells
• Nectin-4: on epithelial cells
(Attachment mediated by H protein)
13
Q
What viral protein mediates membrane fusion and syncytia formation?
A
F (Fusion) protein
14
Q
Where does measles virus replicate in the host cell?
A
In the cytoplasm
15
Q
What are the steps of measles virus replication?
A
- Attachment (H protein)
- Fusion & entry (F protein)
- Replication in cytoplasm
- Transcription & translation
- Assembly & budding at plasma membrane
16
Q
Where does measles virus first replicate?
A
In the respiratory epithelium
17
Q
How does the virus spread in the body after replication?
A
- To local lymph nodes
- Causes primary viremia → spreads to multiple organs
- Secondary viremia → leads to symptoms and skin rash
18
Q
What immune effect does measles virus cause?
A
It induces transient but profound immunosuppression
19
Q
Does measles infection provide lasting immunity?
A
Yes, lifelong immunity after natural infection or vaccination
20
Q
What are the roles of IgM and IgG in measles infection?
A
• IgM: Appears early, marker of recent infection
• IgG: Provides long-term protection
21
Q
Which T cells are involved in eliminating measles-infected cells?
A
CD4+ and CD8+ T cells
22
Q
What does measles-induced immunosuppression cause?
A
Increases susceptibility to other infections
23
Q
According to Prodromal Phase Symptoms
What are the key features of the prodrome phase (2–4 days)?
A
• Fever
• Cough
• Coryza (runny nose)
• Conjunctivitis
→ Known as the 3 C’s
• Koplik spots: small white lesions on buccal mucosa (pathognomonic)
24
Q
According to Exanthem Phase
What characterizes the exanthem (rash) phase of measles?
A
• Maculopapular rash begins on the face, spreads to trunk and limbs
• Rash fades after about 7 days
25
What are the common complications of measles?
• Otitis media
• Pneumonia (most common cause of death)
26
What are the severe complications of measles?
• Encephalitis: can be acute or post-infectious
• SSPE (Subacute Sclerosing Panencephalitis):
Rare, fatal, appears years after infection
27
Who is at higher risk for measles complications?
• Malnourished children
• Immunocompromised individuals
• Infants
28
What is the mainstay of measles treatment?
Supportive care: antipyretics, hydration, and management of complications
29
Why is Vitamin A given in measles, and to whom?
Recommended especially for children — reduces morbidity and mortality
30
Is there a specific antiviral drug for measles?
No, there is no specific antiviral therapy
31
What type of vaccine is used for measles prevention?
Live attenuated MMR or MMRV vaccine
32
What is the measles vaccine schedule and effectiveness?
• First dose: 12–15 months
• Second dose: 4–6 years
• Effectiveness: 93% after 1st, 97% after 2nd dose
33
What are the options for post-exposure prophylaxis?
• MMR vaccine within 72 hours
• Immunoglobulin within 6 days (for high-risk individuals)
34
How many human parainfluenza serotypes are there?
Four serotypes (Types 1 to 4
35
What do parainfluenza types 1, 2, and 3 commonly cause?
• Croup (laryngotracheobronchitis)
• Bronchiolitis
• Pneumonia in children
36
What does parainfluenza type 4 usually cause?
Mild upper respiratory symptoms in children and adults
37
What kind of illness do parainfluenza viruses usually cause?
Mild cold-like illness
38
What are the key surface proteins of parainfluenza viruses and their roles?
• HN (Hemagglutinin-Neuraminidase): Attachment & hemagglutination
• F (Fusion protein): Membrane fusion and syncytia formation
39
Where does parainfluenza virus replicate?
In the cytoplasm
40
Does parainfluenza virus cause viremia?
No, viremia is not common in most cases
41
Where does parainfluenza virus primarily infect?
Epithelial cells of the upper respiratory tract
42
In what percentage of cases does the virus spread to the lower respiratory tract?
About 25% of cases
43
What serious condition can occur in 2–3% of cases?
Laryngotracheobronchitis (Croup)
44
What type of cellular damage is caused by parainfluenza virus?
• Cell lysis
• Syncytia formation
45
Does parainfluenza usually cause systemic infection?
Rarely
46
What role does IgA play in immunity to parainfluenza?
• Provides local mucosal immunity
• Immunity is short-lived
47
What are the effects of cell-mediated immunity?
• Causes tissue damage
• Aids in recovery
48
Does the virus allow long-term immune memory to form?
No, it modulates immunity to prevent long-term memory
49
Is reinfection with parainfluenza virus possible?
Yes, reinfection is common but generally less severe
50
What mild symptoms are caused by parainfluenza viruses?
• Coryza
• Pharyngitis
• Mild bronchitis
• Fever
51
What LRTIs are associated with parainfluenza, especially in infants?
• Bronchiolitis
• Pneumonia
52
What are the hallmark symptoms of croup caused by parainfluenza?
• Barking cough
• Hoarseness
• Inspiratory stridor
• Subglottal swelling → airway obstruction
53
What is the incubation period and typical recovery time for croup?
• Incubation: 2–6 days
• Recovery: Usually within 48 hours
54
What is the seasonal pattern of parainfluenza virus types?
• Type 1 & 2: Autumn outbreaks
• Type 3: Circulates year-round
55
Where do parainfluenza viruses commonly cause outbreaks?
In pediatric wards and nurseries (nosocomial outbreaks)
56
What is the most sensitive and rapid diagnostic test for parainfluenza viruses?
RT-PCR
57
What samples are used for virus isolation in parainfluenza diagnosis?
Nasal washes and respiratory secretions
58
What cell type is commonly used for culturing parainfluenza virus?
Primary monkey kidney cells
59
What specific cytopathic effect is observed in culture for parainfluenza virus?
Syncytia formation
60
What method confirms viral antigens in infected cells?
Immunofluorescence
61
What protein mediates hemadsorption and hemagglutination in parainfluenza?
HN protein (Hemagglutinin-Neuraminidase)
62
What assays are used for serotyping parainfluenza viruses?
• Neutralization assays
• Hemagglutination inhibition assays
63
Is there a specific antiviral therapy for parainfluenza virus?
No, only supportive care
64
How is croup treated in parainfluenza infections?
• Nebulized cold or hot steam
• Corticosteroids (e.g., dexamethasone)
• Monitor for airway obstruction
• Intubation is rarely required
65
Is there a licensed vaccine for parainfluenza virus?
No licensed vaccine is available
66
Why are killed parainfluenza vaccines ineffective?
They fail to induce mucosal and cellular immunity
67
What is the status of live attenuated vaccines for parainfluenza?
Not yet approved
68
What infection control measures help prevent hospital outbreaks?
• Hand hygiene
• Isolation of infected individuals
• Proper respiratory etiquette
69
What is the hallmark clinical manifestation of mumps?
Acute viral parotitis (painful swelling of salivary glands)
70
How has vaccination affected mumps prevalence?
It’s rare in vaccinated populations, but recent outbreaks have occurred
71
How does the mumps virus infect the host?
• HN glycoprotein binds sialic acid on respiratory epithelium
• Spreads to parotid gland via Stensen duct or viremia
72
What immune responses are involved in mumps infection?
• Syncytia formation (cell fusion)
• T-cells help clear infection but also cause glandular swelling
73
Does mumps infection provide long-term immunity?
Yes, lifelong immunity (one serotype only)
74
How is mumps virus transmitted?
Highly contagious via respiratory droplets or direct contact
75
When can asymptomatic individuals spread the virus?
Up to 7 days before symptoms appear
76
What percentage of children were infected by age 15 before vaccines?
Around 90%
77
When do mumps outbreaks typically occur?
In winter and spring, especially in close-contact settings
78
What is the current trend in mumps infection?
Resurgence in unvaccinated populations
79
What contributes to recent mumps outbreaks despite vaccine availability?
• Vaccine hesitancy / noncompliance
• Crowded environments
• Delayed vaccination or waning immunity
80
What is the classic clinical sign of mumps?
Sudden-onset bilateral parotitis with fever and Stensen duct redness
81
What glandular organs besides the parotid can be affected by mumps?
• Orchitis (testes)
• Oophoritis (ovaries)
• Pancreatitis
• Thyroiditis
82
What are the central nervous system complications of mumps?
• Meningitis (in ~10% of cases)
• Encephalitis (in ~0.5% of cases)
83
What are potential complications of mumps?
• Sterility (due to orchitis)
• Rare fatal encephalitis
84
Can glandular or CNS symptoms occur without parotitis?
Yes, they may occur even in the absence of parotid swelling
85
What samples are used for RT-PCR detection of mumps virus?
Saliva, urine, and CSF
86
What serological marker indicates acute mumps infection?
IgM detected by ELISA
87
What cells are used for culturing mumps virus, and what is seen?
• Monkey kidney cells
• Formation of multinucleated giant cells
88
What does hemadsorption detect, and how?
Guinea pig RBCs bind to the HN glycoprotein on infected cells
89
Is there a specific antiviral treatment for mumps?
No, only supportive care (analgesics, hydration)
90
What vaccine is used to prevent mumps?
MMR vaccine using the Jeryl Lynn strain
91
What level of population coverage is needed for herd immunity against mumps?
More than 90%
92
How many antigenic types does RSV have?
Two types: A and B; with multiple strains
93
What distinguishes RSV glycoproteins from others like parainfluenza?
RSV lacks neuraminidase and does not bind sialic acid
94
What age group is most affected by RSV?
Infants — it’s the most common cause of fatal acute respiratory infections in this group
95
How common is RSV reinfection?
• Universal infection by age 2
• Reinfections occur throughout life, even in the elderly
96
How does RSV bind and enter cells?
Binds to cell-surface proteins and heparan sulfate to infect respiratory epithelium
97
What cellular effect does RSV cause?
Syncytia formation (cell fusion)
98
What drives airway damage in RSV infections?
Neutrophil-driven inflammation → airway necrosis → mucus plugs, leading to obstruction
99
When does RSV typically spread, and how?
• Winter epidemics (annual)
• Transmission via aerosols, fomites, and hands
100
Who is at highest risk for severe RSV disease?
• Premature infants
• Children with congenital heart/lung disease
• Elderly in nursing homes
101
Does natural infection prevent future RSV reinfection?
No, natural immunity does not prevent reinfection
102
What happened with the killed RSV vaccine in past trials?
It failed and caused enhanced disease severity
103
What are the mild symptoms of RSV in adults and older children?
Upper respiratory infection (e.g., rhinorrhea)
104
What severe condition does RSV cause in infants?
Bronchiolitis
105
What are the symptoms of RSV bronchiolitis?
• Low-grade fever
• Tachypnea
• Wheezing
• Air trapping
106
Who is at highest risk of fatal RSV infection?
• Premature infants
• Immunocompromised individuals
• Infants with chronic lung disease
107
What can reinfection with RSV cause?
• Common cold
• Asthma exacerbation
108
What is the gold standard for RSV diagnosis?
RT-PCR from nasal washings
109
What antigen detection methods are used for RSV?
• Enzyme immunoassay (EIA)
• Immunofluorescence on exfoliated cells
110
Why is RSV hard to culture?
It requires specialized cell lines
111
What is the cornerstone of RSV treatment?
Supportive care:
• Oxygen therapy
• IV fluids
• Nebulized cold steam
112
What antiviral is used in RSV, and what limits its use?
Aerosolized ribavirin — limited use due to toxicity
113
What monoclonal antibody is used for RSV prevention in high-risk infants?
Palivizumab — given to:
• Premature infants
• Infants with congenital heart/lung disease
114
What infection control strategies are used in hospitals for RSV?
• Isolation of infected infants
• PPE: Handwashing, gowns, masks, goggles
115
Why is there no licensed RSV vaccine?
Inactivated vaccine trials worsened disease due to immune enhancement
116
Which animals are most affected in Newcastle disease virus?
Almost all bird species, especially chickens
117
Is the virus contagious among birds?
Yes, it is highly contagious among poultry.
118
How common is HMPV exposure in children?
Over 90% of children are seropositive by age 5.
119
How is HMPV different from RSV?
It is genetically distinct from RSV and difficult to culture.
120
What is the infection mechanism of HMPV?
It targets the respiratory epithelium, causing cold-like symptoms.
121
What are the symptoms of HMPV infection?
Cough, sore throat, rhinorrhea, fever; wheezing and dyspnea in severe cases.
122
What are the severe complications in some patients?
Bronchiolitis and pneumonia in about 10% of cases.
123
Who are the high-risk groups for severe HMPV infection?
Seronegative children, elderly, and immunocompromised individuals.
124
What is the global burden of HMPV?
Causes annual infections worldwide, with seasonal peaks in winter and spring.
125
How is HMPV transmitted?
Through respiratory droplets and close contact.
126
What is the gold standard for HMPV diagnosis?
RT-PCR is the gold standard test.
127
Is routine testing for HMPV commonly done?
No, routine testing is not commonly performed.
128
What is the treatment for HMPV?
Supportive care: hydration and oxygen therapy.
129
Are there any antiviral drugs or vaccines for HMPV?
No, there are no antivirals or vaccines available.
130
What is the classification of Nipah and Hendra viruses?
They belong to the Paramyxoviridae family and are zoonotic viruses.
131
What is the natural reservoir for Nipah and Hendra viruses?
Fruit bats (flying foxes).
132
What is the transmission cycle of Nipah virus?
Bats → Contaminated fruit or pigs → Humans.
133
What are the clinical features of infection?
Flu-like symptoms that can progress to encephalitis, seizures, and coma.
134
What are the key families of arboviruses?
• Flaviviridae: Dengue, Yellow Fever, Zika, West Nile, Japanese Encephalitis
• Togaviridae: Chikungunya, Eastern/Western Equine Encephalitis
• Bunyaviridae: Rift Valley Fever
135
What are the major clinical outcomes caused by arboviruses?
• Hemorrhagic fevers
• Encephalitis
• Congenital defects
136
What are the common initial symptoms of arboviral infections?
Fever and rash, resembling influenza, rubella, or enterovirus infections.
137
Which arboviruses are associated with encephalitis?
• Eastern Equine Encephalitis (EEE)
• Western Equine Encephalitis (WEE)
• St. Louis Encephalitis
• Japanese Encephalitis
138
Which arboviruses are known to cause hemorrhagic fever?
• Yellow Fever
• Dengue
• Crimean-Congo Hemorrhagic Fever
• Zika Virus
139
How is Yellow Fever transmitted?
By Aedes mosquitoes
140
What are the three transmission cycles of Yellow Fever?
• Sylvatic: Monkey → Mosquito → Monkey
• Mixed: Monkey → Mosquito → Human
• Urban: Human → Mosquito → Human
141
What are the key symptoms of Yellow Fever?
Fever, jaundice, and bleeding.
142
What is the mortality rate of Yellow Fever?
Up to 30%.
143
What is the status of the Yellow Fever vaccine?
A single dose provides lifelong immunity.
144
What mosquitoes transmit Dengue virus?
Aedes aegypti and Aedes albopictus.
145
What are the main symptoms of Dengue?
Sudden fever, headache, muscle/joint pain, and petechial rash.
146
What is a severe complication of Dengue infection?
Dengue Hemorrhagic Fever (DHF).
