Viral Infections Flashcards
Describe the common cold
Symptoms = Rhinitis (inflammation of the nasal mucosa), Pharyngitis (sore throat)
No high fever, LRT involvement, or respiratory distress.
- More common in spring and fall
- Complications = Otitis media, sinus infection, exacerbation of asthma
What are the main viruses that cause common cold?
Rhinovirus - Main causative agent
Coronavirus
Describe Rhinoviruses
Picornavirus family member (small RNA)
- Non enveloped, +ssRNA genome
- Three viral species with 100 serotypes
- Shed in respiratory secretions and transmission through direct contact with nasal secretions, large droplets and contaminated fomites
- extremely low inoculum needed for infection (1-3 days of incubation)
describe pathology of rhinoviruses
1) infection in nasal epithelium
2) viruses is absorbed
3) virus replicates
4) virus sheds epithelium causing host cell defenses to be activated
5) recovery via interferon and ab production (epithelium becomes regenerated with no sign of virus)
describe the treatment of Rhinovirus
Treatment regimens aimed to alleviate symptoms (antihistamines, decongestants
- antibiotics ONLY given in the case of bacterial superinfections
- immune responses to rhinovirus infection can be long lasting in a serotype specific manner (but, many serotypes tho)
- NO VACCINES AVAILABLE
Describe Non-SARS coronavirus
Enveloped with +ssRNA genome
- replicated in the epithelial cells of the respiratory tract
- optimal temp of 33-35 degrees
- transmission occurs through large droplets (3 day incubation period)
- outbreaks common in winter and spring
Treatment and prevention of Non-SARS coronavirus
like rhinoviruses, the treatment for non SARS coronavirus infections is aimed to alleviate symptoms
- No vaccine available
- reinfection can occur despite circulating antibodies
describe adenoviruses
adenovirus family; non enveloped dsDNA genome
- the adenoviral fiber proteins protrude from the 12 vertices of the capsid used for attachment and are toxic to cell
- Lots of serotypes –> 1,2,5 causes respiratory disease
- Transmission: oral, droplet inhalation, conjunctiva
- replicate in epithelial cells causing tissue damage
- may enter lymphoid tissues following acut infection (shed virus for up to 18 months)
- NO SEASONAL PATTERN OF DISEASE
Describe other illnesses associated with adenovirus
= Pharyngoconjunctival fever - conjunctivitis, pharyngitis, fever
= More severe respiratory infections, such as croup, bronchiolitis and pneumonia
= Serotypes 40 and 41 are associated with gastrointestinal disease
describe treatments for adenoviruses
treatment are aimeda t reducing symptoms
- immunity is long-lived but serotype specific
- live oral vaccine to serotypes 4 and 7 for military recruits
Describe Coxsackieviruses
Enterovirus subfamily of picornairuses
- nonenveloped +ssRNA genome
- replication is fast and occurs in the cytoplasm
- able to survive low pH conditions found in GI tract
- Transmitted through the fecal-oral route
- No vaccine available
- recovery generally occurs in a couple of weeks without treatment.
describe Herpangina
Caused by Coxsackievirus
Symptoms:
- Abrupt onset of fever, small vesicles on the soft palate that when they rupture form small white ulcers
- Most common in children 1-7 years old
- complications can e meningitis or encephalitis
Describe Hand-Foot and Mouth disease
Caused by Coxsackievirus
- Symptoms = fever, vesicular lesions on the soles of hands and feet and on oral areas
- most frequent in children
What are other common cold viruses
Influenza viruses - B and C especially
Respiratory syncytial virus - adults and school-aged children
Parainfluenza virus - adults and school-aged children
Describe Croup
Laryngotracheobronchitis
- symptoms develop from swelling of subglottic region of the larynx (fever, brassy cough, inspiratory strider
- radiograph: narrowing of air shadow of trachea in the subglottic area referred to “steeple sign”
- most common in children less than 6 years
- complication include hypoxia
describe the treatment of Croup
Treatment goal = alleviate symtpoms
- If they have a strider at rest (severe) treat with oxygen, epinephrine, glucocorticoids to open airways
- if they have no stridor (mild or moderate) at rest treat with humidified air and hydration
Describe the causes of Croup
Parainfluenza virus:
- Type I is the most common cause of acute Croup
- Type 2-3 can also cause croup (parainfluenza type 3 also causes LRT infection)
Others = respiratory syncytial virus and measles virus
Describe Parainfluenza virus
Paramyxovirus family -ssRNA genome
- RNA synthesis occurs in the cytoplasm
- helical nucleocapsid
- envelope contains hemagglutinin and neuraminidase (targets for immune system)
- Transmission: large droplets/direct contact
- incubation period 2-10 days
- Pathogenesis = Infect, replicate in the ciliated epithelium of the respiratory tract
- Short lived immunity; reinfection usually results in less severe illness.
Describe Symptoms of Influenza
Myalgia, Headache, Fever, Shaking Chills,
- Cough peaking between 3 and 5 days of illness
- Cough, fatigue, and generalized weakness may last 2-6weeks
- Increased severity of symptoms and incidence of complications usually seen in pandemic outbreaks
- In temperate climates the infections peak during the winter months
- Incubation lasts 2 days
Describe the risk groups for complications to Influenza
- Children younger than 2yo
- adults 65 years or older
- pregnant women and women up to 2 weeks postpartum
- Persons with certain medical conditions
What is the biggest side effect of Influenza
Pneumonia = inflammation of the lung parenchyma leading to abnormal gas exchange Symptoms = Fever, chills, cough, pleuritic chest pain, increases respiratory rate, wheezes and crackles, hypoxia and cyanosis (severe cases)
Describe Primary influenza virus pneumonia
Primary influenza virus pneumonia
- -> usually influenza A
- -> Symptoms = 1-4 days of influenza virus symtpoms, than increased cough, tachypnea, dyspnea, acute respiratory distress.
- -> Sputum Gram Stain shows Abundant PMN cells w/o bacteria
Describe Bacterial influenza-associated pneumonia
usually onset a week after influenza symptoms began
- Symptoms = Influenza symptoms, which lessen, then followed by increased cough, return of fever, and respiratory distress
- Sputum Gram stain may contain bacterial cause
- Etiology: 1) S. Pneumoniae
2) S. Aureus and H. Influenzae
3) Others: N. meningitidis, other streptococcus and gram negative bacillus
Cause of Influenza virus
Orthomyxovirus: segmented, -ssRNA virus genome, enveloped
Contains two proteins on surface: (important targets)
1) Hemagglutinin (H) = attachment and agglutinates RBC
2) Neuraminidase (N) = cleaves sialic acid, virion release/spread
