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Virology > Measles > Flashcards

Measles Flashcards

1
Q

Why do Measles and Rubella meet the necessary criteria for disease eradication?

A

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

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1
Q

What is the UK target for MMR coverage?

A

> 95% coverage of 2x doses of MMR in routine childhood immunisation schedule (<5 years old)

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2
Q

What is the incubation period of Measles?

A

7-21 days

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3
Q

What is the R0 number for Measles?

A

R0 is estimated 15-20

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4
Q

What are the primary symptoms of Measles?

A

Generally very unwell

Fever >39degC

Maculopapular rash

Conjunctivitis

Coryzal symptoms

Cough

Koplik’s spots

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5
Q

Measles rash

What are other common differential diagnoses?

A

Rubella

HHV6 - although usually <1 year old

Parvovirus

Scarlet fever - GAS

S. aureus with toxic shock

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6
Q

What are severe complications of Measles?

A

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

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7
Q

What is a breakthrough Measles infection?

A

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

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8
Q

1 year old child develops maculopapular rash 10 days following vaccination

What is the management?

A

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

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9
Q

What family of viruses does Measles belong to?

A

Paramyxoviridae family

Morbiillivirus genus

-ssRNA

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10
Q

Measles case definitions

What do these terms mean:

Laboratory confirmed

Probable case

Possible case

A

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

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11
Q

Which contacts are at high risk following a measles exposure?

A

Immunosuppressed

Pregnant women

Children <1 year old

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12
Q

What constitutes a measles contact?

A

household contact

face-face contact (<2m)

> 15 mins in the same room or hospital bay

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13
Q

Immunosuppressed measles contact

What is the difference between Group A and Group B categories of immunosuppression?

A

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

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14
Q

Immunosuppressed measles contact

What is the management of Group A and Group B contacts

A

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

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15
Q

When does HNIG need to be administered?

A

Within 6 days of exposure, as incubation period is 7-21 days

16
Q

Pregnant measles contact

What is the management

A

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

17
Q

Measles contact

What is the management for these children

<6 months old
6-8 months old
9 months or older

A

<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

18
Q

Immunosuppressed patient inadvertently given MMR vaccine

What action should you take?

A

Manage as usual on guidelines following exposure

If immunosuppressed, likely to need HNIG

19
Q

Pregnant patient inadvertently given MMR vaccine

What action should you take?

A

Immunocompetent, so no HNIG required as unlikely to develops disease

Should be reported

20
Q

Child with measles

How long should they be excluded from school?

A

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

21
Q

Question from Samir

Why have cases of Measles risen recently?

A

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

22
Q

R0 of Measles is 15 which is the basic reproductive value

What is the effective reproductive value?

A

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

23
Q

What are IP&C precautions for confirmed Measles infection requiring admission?

A

Negative pressure side room

FFP3 - droplet/ airborne transmission

Visor

Gloves

Gown

24
Q

Measles and Rubella in differential diagnosis of rash

How to distinguish clinically?

A

Measles -
more unwell
conjuctivitis only in measles

Epidemiologically -
current Measles outbreak in UK
no Rubella cases in UK

25
Q

4 year old with fever ,coryza, rash

What further information do you want?

A

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

26
Q

When does rash appear in Measles?

A

Immune mediated

Appears day 2-4 after symptoms start

27
Q

How to diagnose Measles CNS infection?

Acute encephalitis
Post-infectious (ADEM)
SSPE

A

Acute encephalitis/ SSPE - both have Measles RNA detected in CSF

28
Q

Pregnant woman is Measles contact

Has IgG detected

Why is further HNIG not given to boost protection?

A

Level of antibody in blood if detected, is massively higher than what can be achieved with HNIG

29
Q

Measles contact who is immunosuppressed

Cat A

What is management?

A

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

30
Q

Measles contact who is immunosuppressed

Cat B

What is management?

A

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

Virology (56 decks)

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