Complications in Influenza?
- Pneumonia (though rare to get pneumonia from a viral infection, mortality is high such as in bird flu). May also come about from a secondary bacterial infection because the bronchial mucosa is damaged - Beware of a secondary bacterial LRTI!
○ Strep pneumo, H inf, Staph aureus
○ Common in extremes of age, immunocomps, pts with existing chronic cardiorespiratory diseases
○ Suspected in chest pain, persistent productive cough- Myocarditis
- Myositis
- Reye’s Syndrome - A/w giving aspirin to kids with influenza B. Causes cerebral oedema, fatty liver degeneration; High mortality
Some severe variants, like H5N1, have a 60% mortality
Clinical presentation of influenza?
- Epidemic disease, occasional pandemics (swine flu 2009)
- 1-4 day incubation followed by abrupt onset fever, myalgia, malaise, headache, rhinorrhea, sneezing, sore throat, dry cough
- The virus multiplies in the respiratory epithelium, causing damage to the ciliary escalator and resulting in desquamation (death of squamous epithelium and sloughing of cells that causes the sore throat)
What are the antigens of influenza
- Hemagglutinin (spikes for viral attachment to host; causes agglutination of RBC of different animals. This is inhibited by haemagglutinin inhibition (HI), and HI is a test that can be done)
- Neuraminidase (cleaves neuraminic acid // sialic acid receptors so as to allow virus release)
Soluble // “S” antigen shared by all influenza viruses of the same type
- Neuraminidase (cleaves neuraminic acid // sialic acid receptors so as to allow virus release)
Antigenic drift vs shift?
- Antigenic shift occurs from recombination of RNA segments of two different virions infecting the same cell (i.e. 16 possible segments to PnC into a new virion)
○ Major antigenic change of both surface proteins (H and N)
○ Common in pigs as they can be infected by birds and humans; “Mixing vessel”, though the largest reservoir for viruses is wild birds - Antigenic drift because spontaneous mutations occur more readily because of RNA polymerase (tends to make more mistakes than DNA polymerase).
Curative influenza tx?
- Curative treatment:
○ Neuraminidase inhibitors (Oseltamivir, Zanamivir)
○ Polymerase inhibitors (Baloxavir)
○ Amantadine is used to prevent viral replication, but resistance is common!
Outline prophylactic influenza immunization
Quadrivalent vaccine, only 15% coverage (annual vaccines available)
○ The immunity doesn’t last very long ○ Guillain-Barre syndrome in rare cases ○ Coverage in SG is very low, but still encouraged!
What family is parainfluenza in?
Paramyxovirus
Recall that influena is orthomyxovirus
Outline clinical presentation of influenza
We get infected by age 5. Types 1, 2, 3, 4 exist and have considerable overlap, but key features are as follows:
- Croup in infants
○ Acute laryngo-tracheo-bronchitis / coughing and hoarsness / stridor, dyspnoea, cyanosis. May require tracheostomy!
○ Ddx is diphtheria, Epiglottitis from Hinf if any
- Epidemics in winter
- Bronchiolitis and bronchopneumonia in infants / Croup in older infants
Minor respiratory infection
Any vax for parainfluenza?
No vaccine
Management of parainfluenza?
- No vaccine
- Ventilatory support may be required
- Abx in case of a secondary bacterial infection
- Keep them hydrated! Sedation may be required too
Outline clinical RSV
Clinically:
- The commonest cause of bronchiolitis in young children (PEAKS AT 3 MONTHS OLD! As always, more serious in extremes of age and immunocomps)
- Fever, cough, dyspnoea / tachypnoea, wheezing (LRT expiratory sound!), cyanosis; Immune mediated or mechanically- induced inflammatory bronchiole obstruction
○ Severe pneumonia may occur if there is interaction between the virus and maternal Ab. Bronchiolitis too! Up to 5% mortality in bronchiolitis
○ Secondary bacterial infection
○ Otitis media
○ HF
○ Apnoea
- CNS malformations / Congenital heart and lung diseases = High mortality!
In older children / adults, just causes a URTI because the bronchioles are bigger
Management of RSV?
- Ribavirin aerosol (antiviral straight to the lungs; given only if severe) / Ventilatory support
- Isolate infected children
- Vaccines:
○ RSV monoclonal Ab injections before / during RSV seasons (prophylactic immunoglobulin)
○ Actual RSV vaccine approved in 2023 for >60y/o
How many RSV serotypes are there
ONE
What genus newly found has similar symptoms to RSV?
Metapneumovirus
Clinical presentation of adenovirus?
Think mucosal tissues and conjunctiva! Called adenovirus because they were isolated from the adenoids (lymphoid tissue in pharynx); Certain human strains actually cause malignant cancer in baby hamsters but not in us.
Clinically:
- Pharyngoconjunctival fever (think swimming pools / occasional epidemics)
- Just a URTI and fever
- Pneumonia
- Acute follicular conjunctivitis, Epidemic keratoconjunctivitis aka Shipyard eye
- Haemorrhagic cystitis (urinary bladder haemorrhage!)
- Enteritis too! Think of mesenteric adenitis (lymph nodes of the mesentery) and intussusception
Chronic infection of tonsils, adenoids
How many serotypes of Rhinovirus?
> 100! Causative agent in common coldC
Clinical presentation of rhinovirus?
- 2-4 day incubation with infection lasting 1-2w
- Coryza symptoms - Rhinorrhoea, sneezing, sore throat, cough, mild fever, hoarseness of voice and headache
- Complications of sinusitis, otitis media (through the Eustachian), pneumonia.
- Precipitates asthma attacks, aggravates chronic bronchitis
- Spreads a lot in rains/ close contacts / aerosolized droplets and respiratory secretions
What does the vaccine for rhinovirus contain?
Trick question
There is no rhinovirus vax!
Optimum rhinovirus growth?
In the nose! Because 33C temp
Below pH6, the virus becomes unstable
Mortality rate of MERS?
25%!
