Download 3 Measles Epidemiology

History
• The earliest description of measles- Arab physician,
Abubacr (865-925 A.D.)
• Classical studies on the epidemiology of measlesPanum, 1846
• Measles virus isolated- Enders and his colleagues,
USA(1954)
• Measles vaccine first used in a clinical trial-1958
• Live measles vaccine licensed for use-1963
Introduction
• A distinct clinical disease associated with high morbidity
and mortality rates in early childhood.
• Also called RUBEOLA (red spot)
• A highly acute viral infectious disease affecting nearly
every person in a given population in the absence of
immunization
• More than 30 million cases/year
• 875000 deaths/year from measles or its complications
• Kills more children than any other vaccine preventable
diseases; represents 50 to 60% of estimated deaths
attributable to childhood vaccine preventable diseases
• More severe in infants and adult than in children
• Crowding and poverty in close contact with large
numbers of non-immunized people – contributing factors
for measles outbreaks.
Case definition
• any person with fever of 38 degree Celsius or more (hot
to touch) and Maculo-papular rash and at least one of
the following: Cough, Coryza or conjunctivitis or any
person in whom a health professional suspects measles”.
Characteristics
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Fever
Dry cough
Runny nose
Inflamed eyes (conjunctivitis)
Sensitivity to light
Tiny red spots with bluish-white centers on the inner
lining of the cheek, called Koplik's spots
Complications
• Varies from country to country; occurs in 10-15% of
cases
• Common in Nepal - Otitis media, pneumonia, diarrhea
followed by malnutrition, Corneal ulcer and post infection
encephalitis (rarely).
• Others:- Orchitis (13-15% of adult male cases;
rare in childhood)
- sterility, oophritis & mastitis
(occasionally)
- pancreatitits (very rarely)
- meningoencephatitis (without
involvement of salivary gland.)
• Measles infection during pregnancy is associated with
spontaneous abortion and delivery of LBW infants
• Rare reports of congenital malformation associated with
measles during the first trimester
• No evidence for the congenital measles syndromes
• Approx.1/1,00,000 cases can result in degenerative disorders
of CNS known as sub-acute sclerosing panencephalitis (SSPE)
Risk factors
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Age: higher CFRs in younger age group ( 6-18 mth)
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Gender: In two studies from Asia, CFRs for females >
males
In Bangladesh CFR for Male (0.98%) < females
(2.64%) but no differences documented in African
studies (see below)
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Socio economic status: poverty, over-crowding
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Intensity of exposure: Increased rates of mortality
in secondary cases at home.
• Nutritional status: High mortality in under nourished
population but no studies have proven individual nutritional
status as a reliable predictor of mortality (?)
• Absent or delayed medical care:
-most mortality be prevented through timely and
appropriate medical care.
-rare in developing countries
• Local treatment:
-Measles
normal event
work of Witches or sorcerers
(cultural concept).
-local treatments, restrictions on fluids/food, delay in
access to effective chemotherapy and use of potential toxic
substances potential contributors to increased mortality.
• Non- vaccination:
Vaccination status- the single most important
determinant of measles morbidity and mortality
Almost all unprotected children eventually be
infected with measles and 1-5% will die.
WORLD SITUATION
• In 2007, there were 197 000 measles deaths
globally - nearly 540 deaths every day or 22
deaths every hour.
• More than 95% of measles deaths occur in
low-income countries with weak health
infrastructure. 85% of deaths occur in
SEAR.
50-60% of estimated deaths attributable to
childhood vaccine preventable diseases
• Measles vaccination has caused 74% drop
in measles deaths between 2000 and 2007
worldwide - a drop of about 90% in the
eastern Mediterranean and Africa regions.
(WHO, 2007)
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SITUATION IN NEPAL
• Measles affects 1,50,000 children every year
in Nepal, causes about 5000 deaths
annually, renders thousands others blind
and cause mental disability.
(UNICEF, 2009)
• Measles remain endemic in Nepal with
epidemics occurring every 2-3 years
EPIDEMIOLOGY
1. Agent factors:
-Single strained RNA virus of paramyxo virus
group
-Only 1 serotype known
-Very sensitive to acid conditions, drying, and
light but can survive well in aerosolized
droplets
-Virus can remain viable for at least 34 hours
at room temperature
-During the prodeermal period and for a short time
after the rash appears, virus sheds in
nasopharyngeal secretion, blood and urine.
2. Host Factors:
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Age: 6 mths-3 yrs (developing countries)
>5 yrs (developed countries)
Sex: Incidence equal in both male and female
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Immunity: No immunity unless immunized/natural
immunity
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Nutrition:-very severe in malnourished child
-mortality 400 times higher in malnourished
-Severely malnourished children excrete virus
for longer periods than better-nourished
indicating prolonged risk to them and of
intensity of spread to other
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Environmental factors:
Can spread in any season if suitable climate but in
temperate climates, it is a winter disease (coz)
Mode of transmission
 Droplet infection
 Droplet nuclei
(4 days before onset of disease till 5 days
thereafter )
 Infection through conjunctiva (likely)
The portal of entry - respiratory tract.
Rate of infection depends on
• his/her immune status
• population size and density of the community and
• frequency of individuals contact with other
infectious persons(90% of contacts develop
disease)
Incubation period
-approx. 10-12 days to the first prodromal symptoms
and another 2-4 days to the appearance of the rash.
-When measles infection artificially induced, the
incubation period somewhat shortened, i.e. 7 days
Clinical features
Measles has three clinical stages: -
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Prodromal stage
Eruptive stage
Post measles stage
Measles elimination Campaign
• WHO has proposed to eliminate measles .
• This refers to the interruption of transmission in a
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sizeable geographical area.
The global eradication of measles is technically plausible
with currently available vaccines because it is very
unlikely that non-human reservoirs could sustain
measles transmission. However, for eradication of
measles, more than one dose vaccine is recommended
as a strategy. WHO categorizes countries in three
“Phases” of elimination and Nepal falls into the lowest
rank, some innovative strategy need to be developed
and implemented.
High level of immunization coverage important factor.
Following measures have been recommended
• Children with measles should be kept out of school for 4
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days after appearance of the rash. In hospital respiratory
isolation from onset of catarrhal stage of the prodromal
period through 4th day of rash to reduce the exposure of
other patients at high risk.
Usually quarantine not practical but sometimes
quarantine of institution ward or dormitories can be of
value, strict segregation of infants if measles occur in
institutions.
Investigation of the contracts and source of infection: a
search for an immunization of exposed susceptible
contract be carried out to limit the spread of disease.
National policy and strategy:
Goal:
To reduce the infant and child morbidity and
mortality associated with measles disease.
Objectives:
To reduce measles cases by 30% and measles
death by 95% from previous levels by the year 2005
(according to child heath profile of Nepal 2003 or
WHO, UNICEF, Global measles strategic plan 20012005 seeks to reduce measles mortality worldwide in a
sustainable way by 50% relative to 1999 estimates.
Strategies for measles mortality
reduction
• Improved routine immunization 90% or more
• Strengthen measles surveillance with integration of
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epidemiological and laboratory information.
Improved case management with Vitamin A
supplementation.
Supplemental measles immunization
WHO measles elimination
strategy
• Catch-up: One time nation wide vaccination
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campaigning targeting usually all children aged 9 months
to 14 years regardless of history of measles disease or
vaccination status.
Keep-up: Routine services aimed at vaccinating more
than 95% of each successive birth cohort.
Follow-up: Subsequent nation wide vaccination
campaign every 2-4 years targeting all children born
after the catch-up campaigning.
Challenges in Measles
Eradication
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Increasing measles immunization coverage to a level
of at least 95%.
Rescheduling or two-dose policy in measles
immunization.
Addressing missed opportunity adequately.
Cold chain maintenance for securing vaccine
potency/efficacy.
Safe injection practices in immunization.
Better case management of measles cases.
Active surveillance of measles cases.
Clear guidelines on “Outbreak Response
Immunization”: Vaccination during outbreak of
measles.
Constraints: • Very difficult to maintain cold chain due to the
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various topographical situation.
Lack of motivation or willingness in the side of
health workers.
Poor inter and intra-sectoral co-ordination.
Lack of KAP on measles vaccination of the
general population, which has caused high
dropout rates in the vaccination.
RECOMMENDATIONS
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Effective co-ordination between different sectors be
maintained.
Good governance of the program be made.
Reporting system be strengthened.
Effective training for the health workers be conducted
regularly.
Effective surveillance system be conducted.
Motivation and follow-up mechanisms to be developed
for VDCs to support FCHVs.
References
1. Preventive and Social Medicine. Park and park 17th
2.
3.
4.
5.
edition.
Annual Report-2002/03.p.25- DHS
Child health situation in Nepal: - CHD
Polio Eradication Nepal-hands out.
Control of Communicable Disease Manual
2003;EDCD/MOH/DHS.