Virology Basics Flashcards
If a country has ‘eliminated endemic measles’, how would this be defined?
The WHO define elimination of endemic measles as the absence of endemic measles in circulation for at least 12 months in a country with a high-quality surveillance system.
The WHO target for MMR vaccine update is greater than or equal to 95%.
To maintain elimination status, surveillance needs to be highly sensitive to detect sporadic cases and to classify cases as endemic or imported.
Outbreaks in recent years have occured in cohorts like the Charedi Orthodox Jewish communities, Traveller communites, Anthroposophic (Steiner) communities and migrants, where vaccine uptake is suboptimal.
When should you notify UKHSA of measles?
Measles is notifiable upon suspicion.
What is ‘breakthrough measles’?
Breakthrough measles (previously referred to as reinfection) is uncommon and occurs in those who are immune, typically at least 6 years after full vaccination (two doses of MMR).
It tends to occur after exposure to active measles, and tends to be much less infectious with risk of transmission only to immunosuppressed.
What is the average incubation period for measles?
What is the period of infectiousness?
What is the route of transmission?
The incubation period is typically around 10-12 days from exposure to onset of symptoms, but can vary from 7 - 21 days.
The period of infectiousness generally starts from 4 days before the rash and lasts up to 4 days after the rash.
The transmission route of measles is mostly airborne by droplet spread or direct contact with nasal or throat secretions of infected persons.
Much less commonly, measles may be transmitted by articles freshly soiled with nose/throat secretions, or through airborne transmission with no known face-to-face contact.
What are the common symptoms of measles?
Measles typically starts with a 2-4 day prodromal phase before the rash appears, which includes high fever, coryzal symptoms, cough and conjunctivitis.
Symptoms typically peak on first day of rash.
The red blotchy maculopapular rash usually starts on face and behind the ears, expanding to the trunk.
The rash is NOT itchy, and generally lasts 3-7 days.
Koplik spots may appear a day before the rash. These are small white or bluish lesions on an erythematous base on the buccal mocosa (inner lining of the cheeks).
Name and describe possible complications of measles infection
- viral pneumonitis (usually develops within 2 weeks of symptom onset). This is the most common cause of death in immunosuppressed individuals. Pts at highest risk include those with severely impaired cell-mediated immunity such as bone marrow transplants, pts with T cell dysfunction, AIDS or ALL.
- otitis media
- diarrhoea
- often leads to a temporary reduction in immune responses in the few weeks following infection, which may increase the risk of severe secondary bacterial and viral infections.
- Tracheobronchitis (‘measles croup’) and pneumonia due to secondary bacterial infection are frequent complications of measles.
Encephalitis occurs rarely, 0.05 - 0.1% of measles cases.
Subacute sclerosing panencephalitis (SSPE) is a very rare but very severe complication, occuring in 0.01% of cases.
SSPE presents a few years after measles infection with progressive neuro-cognitive symptoms. Most cases lead to coma and death.
The risk of SSPE is increased in children who acquire measles before the age of 1.
What happens if you get measles during pregnancy?
Measles can be severe in pregnant women and increases the risk of prematurity and foetal loss, although there is NO evidence that it causes congenital defects.
