Measles in WADr Sharon NowrojeeNorth Metropolitan Public Health UnitSCGH 04 September 2014

Measles

•Although incidence is decreasing, still causes approximately 120 000 deaths each year worldwide (WHO 2012)

•Currently various outbreaks occurring in SE Asia - China 42 000 cases to date 2014,

- Philippines 16 000, - Vietnam 3700 - Japan 400.

Australian Notifications

•297 cases so far reported in Australia this year, 39 in Western Australia.

•Complications can include pneumonia, otitis media, 1/1000 encephalitis

•1/100 000 subacute sclerosing panencpehalitis (SSPE) several years after.

• Infection in pregnancy and in infants can be severe.

Measles

•Measles is one of the most infectious disease with one of the highest R0

•basic reproduction number (denoted R0, r nought) of an infection can be thought of as the number of cases one case generates on average over the course of its infectious period, in an otherwise uninfected population

Basic Reproductive Rate

•The basic reproductive rate is affected by the following factors:

B - The infectiousness of the organismN - The number of susceptible people with whom the infected patient comes in contactD - The duration of infectivity

R0 = B * N * D

R0 = B * N * D

• Infectiousness: Airborne versus Droplet

•Susceptible contacts: Mitigate through vaccination. Higher the R0 the higher the herd immunity needed.

•Duration of infectiousness: 9 days for measles, 3 weeks for pertussis.

Basic reproduction number

Disease R0 Herd Immunity

Measles 12-18 95%

Pertussis 12-17 95%

Chickenpox 9-10 95%

Mumps 4-7 75-86%

Rubella 6-7 85%

Smallpox 5-7 80%

Polio 5-7 80-86%

HIV/AIDS 2-3

Influenza (1918) 2-3

SARS 2-5

Ebola 1-4

Measles contact tracing

• Incubation period usually 10 days (varies 7-21)• Infectious period from 5 days before rash to 4 days

after rash •Susceptible contacts – anyone born after 1966

without 2 documented vaccinations or proof of immunity.

•Prophylaxis involves vaccination within 72 hours of exposure

•NHIG within 144 hours (pregnant, infants, immunosuppressed)

Measles case 1

•28 year old male•Holiday in Bali. Returned 28 Sept•02 Oct fever, headaches, lethargy, sore throat•Saw GP 04 October•05 Oct rash associated with dry cough•SCGH 08 October. Isolated after ½ hour • ‘Mild injection both eyes’•Unvaccinated (parents were vaccine refusers)

Contact Tracing

•Household (brother also unvaccinated)•Girlfriend•Visit to electronics shop•GP surgery 14 contacts (incl 5 mo baby)•SCGH Hospital (17 patients born after 1966)•SCGH staff

Case Example 2

•25 year old FIFO worker •Holiday in Bali. Returned 29 Sept•06 October fever, cough, coryza, sore throat•Seen 3x at mine site clinic•09 Oct rash on trunk, abdo and back.•Flew to Perth 09 Oct (charter flight)•Seen at SCGH evening 09 Oct

Case Example 2

•Arrived ED Assessment 20:17• Isolated in ED cubicle 20:45 then neg pressure

room. (Measles case the night before)

Contact Tracing

•Household contacts•Mine site work contacts (2 teams)•Mine site clinic contacts•Charter flight passengers and crew•2x taxi drivers•19 ED patients traced including 2 babies

accompanying and one pregnant woman•ED staff

Case Example 3• 20 year old male. • Travelled to Singapore 8-16 June• URTI, fever 19 June• Rash on face 20 June• Went to ED 21 June Dx Virus infection and home.• Saw GP 23 June – History of fever, chills, cough, sore

throat, “gritty eyes”, runny nose, facial rash. Dx Viral illness

• Felt worse 24 June and went back to ED – notes conjunctivitis, florid facial rash moving down the body, Fever 39.6

Contact tracing• Many!• Household• First hospital presentation• GP visit – 34 patients, staff, • Second hospital presentation. In single cubicle but

moved to negative pressure room after 2.5 hours.• 3 secondary cases resulted from ED visit.

Testing

•SerologyIgM may be negative early in infection. 50% sensitivity at 4 days after rash onset.

•PCR for measles virus RNAApproaches 100% sensitivity and sensitivity

Throat swab, urine, blood, CSF

Take home messages

• Need vigilant triage. Measles is very infectious.

• Measles may present with non specific symptoms of

fever, cough, sore throat, coryza, sore eyes,

conjunctivitis. Rash comes 2-7 days later.

• Always ask about recent travel in the preceding 3 weeks.

• Ask about vaccination history.

• Think measles! Implement airborne precautions ASAP.

Measles Rash

Attenuated illness