Measles Flashcards
Why do Measles and Rubella meet the necessary criteria for disease eradication?
there is no animal or environmental reservoir and humans are critical to maintaining transmission
accurate diagnostic tests are available
vaccines and existing vaccination strategies for both diseases are highly effective and safe: the vaccine effectiveness of MMR is more than 90% for a single dose and more than 95% for two doses
transmission has been interrupted in a large geographic area for a
prolonged period of time
What is the UK target for MMR coverage?
> 95% coverage of 2x doses of MMR in routine childhood immunisation schedule (<5 years old)
What is the incubation period of Measles?
7-21 days
What is the R0 number for Measles?
R0 is estimated 15-20
What are the primary symptoms of Measles?
Generally very unwell
Fever >39degC
Maculopapular rash
Conjunctivitis
Coryzal symptoms
Cough
Koplik’s spots
Measles rash
What are other common differential diagnoses?
Rubella
HHV6 - although usually <1 year old
Parvovirus
Scarlet fever - GAS
S. aureus with toxic shock
What are severe complications of Measles?
Pneumonitis
Otitis media
acute infectious Encephalitis 0.1% of cases - during infection
Post-infection encephalitis - auto-immune origin. week to months after initial infection
SSPE - years after initial infection
What is a breakthrough Measles infection?
Infection in a person who has been shown to be previously immune e.g reinfection
Usually happens as person gets older and immunity wanes, combined with an intense exposure
Illness is often milder and shorter duration
1 year old child develops maculopapular rash 10 days following vaccination
What is the management?
Rash could either be due to vaccine, or a co-incidental measles infection
Send oral fluid swab for Measles testing, and needs typing to check if vaccine strain
Infection control
Public health notification
What family of viruses does Measles belong to?
Paramyxoviridae family
Morbiillivirus genus
-ssRNA
Measles case definitions
What do these terms mean:
Laboratory confirmed
Probable case
Possible case
Laboratory confirmed
laboratory testing confirms result, in suspected case
Probable case
clinical syndrome compatible
non-immune
epidemiological link to another case
Possible case
similar to probable, but clinical syndrome and epidemiological links are both weak
Which contacts are at high risk following a measles exposure?
Immunosuppressed
Pregnant women
Children <1 year old
What constitutes a measles contact?
household contact
face-face contact (<2m)
> 15 mins in the same room or hospital bay
Immunosuppressed measles contact
What is the difference between Group A and Group B categories of immunosuppression?
Groups differentiated based on their likely ability to maintain adequate antibody from past exposure or vaccination
Group A
Should be able to develop and maintain and antibody response
Group B
unlikely to develop or keep an antibody response
Immunosuppressed measles contact
What is the management of Group A and Group B contacts
Group A
- Previous IgG pos - do not give IVIG
- Undocumented IgG status - check IgG level. If non-immune, give IVIG
- History of 2x MMR vaccines - check IgG level. If non-immune, give IVIG
Group B
- offer IVIG regardless of status
- if recently finished immunosuppressive treatment, then can check IgG, and if positive can avoid giving IVIG
When does HNIG need to be administered?
Within 6 days of exposure, as incubation period is 7-21 days
Pregnant measles contact
What is the management
Assume immune:
- history of previous infection
- documented 2x MMR vaccines
1 or zero measles vaccines - check Measles IgG. If negative, give HNIG within 6 days of exposure
Measles contact
What is the management for these children
<6 months old
6-8 months old
9 months or older
<6 months old
assume susceptible
give HNIG regardless of maternal status
6-8 months old
assume susceptible, regardless of maternal status
household exposure - HNIG
exposure outside house - administer MMR
9 months or older
administer MMR within 72 hours of expsoure
Immunosuppressed patient inadvertently given MMR vaccine
What action should you take?
Manage as usual on guidelines following exposure
If immunosuppressed, likely to need HNIG
Pregnant patient inadvertently given MMR vaccine
What action should you take?
Immunocompetent, so no HNIG required as unlikely to develops disease
Should be reported
Child with measles
How long should they be excluded from school?
Infectious from 4 days before rash, to 4 days after rash
so can return after 4 complete days. However would only advise to return if child has made a full recovery
Question from Samir
Why have cases of Measles risen recently?
Covid pandemic - large number of people not immunised.
Now below population herd immunity level of 95%
Large susceptible population
Highly virulent disease with high R0 value
War/ climate/ travel - migration - import of infections
Vaccine hesitancy following covid
R0 of Measles is 15 which is the basic reproductive value
What is the effective reproductive value?
Effective reproductive value Re
is the basic reproduction value (15) multiplied by the proportion of the population who are susceptible to Measles.
Re below 0.7 can eliminate Measles
Re between 0.7 and 1.0 can still cause outbreaks, depending on mixing patterns of high risk individuals. e.g a religious group does not get vaccinated
Vaccination of population aims to keep the number of susceptible contacts low, in order to interrupt chain of transmission
What are IP&C precautions for confirmed Measles infection requiring admission?
Negative pressure side room
FFP3 - droplet/ airborne transmission
Visor
Gloves
Gown
Measles and Rubella in differential diagnosis of rash
How to distinguish clinically?
Measles -
more unwell
conjuctivitis only in measles
Epidemiologically -
current Measles outbreak in UK
no Rubella cases in UK
4 year old with fever ,coryza, rash
What further information do you want?
PMHx
MMR vaccine
Unwell contacts
Foreign travel
Member of travelling (anti-vax) community
What is rash like - erythematous, maculopapular
What is distribution - start of head, more to torso, then extremities
When does rash appear in Measles?
Immune mediated
Appears day 2-4 after symptoms start
How to diagnose Measles CNS infection?
Acute encephalitis
Post-infectious (ADEM)
SSPE
Acute encephalitis/ SSPE - both have Measles RNA detected in CSF
Pregnant woman is Measles contact
Has IgG detected
Why is further HNIG not given to boost protection?
Level of antibody in blood if detected, is massively higher than what can be achieved with HNIG
Measles contact who is immunosuppressed
Cat A
What is management?
Cat A - expected to develop and maintain antibody response
Test for Measles IgG, even if know to have had 2x MMR vaccines
IgG detected - consider immune
IgG not detected - give HNIG
Measles contact who is immunosuppressed
Cat B
What is management?
Cat B - not expect to develop and maintain antibody response
Give IVIG - assume susceptible
If has completed there immunosuppression e.g chemotherapy, then check IgG. If immune, then does not need IVIG
