|
IAC Express 2008 |
| Issue number 728: May 5, 2008 |
| |
Contents
of this Issue
Select a title to jump to the article. |
- CDC
publishes MMWR Early Release about U.S. measles outbreaks during January
1-April 25, 2008
|
| |
| Abbreviations |
|
|
AAFP, American Academy of Family Physicians; AAP,
American Academy of Pediatrics; ACIP, Advisory Committee on Immunization
Practices; AMA, American Medical Association; CDC, Centers for Disease
Control and Prevention; FDA, Food and Drug Administration; IAC, Immunization
Action Coalition; MMWR, Morbidity and Mortality Weekly Report; NCIRD,
National Center for Immunization and Respiratory Diseases; NIVS, National
Influenza Vaccine Summit; VIS, Vaccine Information Statement; VPD,
vaccine-preventable disease; WHO, World Health Organization. |
| |
|
Issue 728: May 5, 2008 |
|
|
|
1. |
CDC publishes MMWR Early Release about U.S. measles outbreaks during January
1-April 25, 2008
On May 1, CDC published "Measles--United States,
January 1-April
25, 2008" as an MMWR Early Release. CDC publishes the web-based
MMWR Early Release only for the immediate release of important
public health information. The article will be published in the
standard MMWR format in the future. The article is reprinted below
in its entirety, excluding one figure and references.
Links to three related CDC resources appear at the end of this IAC
Express article. The three resources are (1) the transcript of a
CDC press briefing, "CDC Update on Measles Outbreaks in the United
States," which was held on May 1, (2) "Fact Sheet: Measles, United
States, January 1-April 25, 2008," which was issued on May 1, and
(3) "Measles Update: Measles Outbreaks Continue in U.S." which was
recently posted in the Features section of CDC's homepage.
Measles, a highly contagious acute viral disease, can result in
serious complications and death. As a result of a successful U.S.
vaccination program, measles elimination (i.e., interruption of
endemic measles transmission) was declared in the United States in
2000. The number of reported measles cases has declined from
763,094 in 1958 to fewer than 150 cases reported per year since
1997. During 2000-2007, a total of 29-116 measles cases (mean: 62,
median: 56) were reported annually. However, during January 1-April
25, 2008, a total of 64 confirmed measles cases were preliminarily
reported to CDC, the most reported by this date for any year since
2001. Of the 64 cases, 54 were associated with importation of
measles from other countries into the United States, and 63 of the
64 patients were unvaccinated or had unknown or undocumented
vaccination status. This report describes the 64 cases and provides
guidance for preventing measles transmission and controlling
outbreaks through vaccination, infection control, and rapid public
health response. Because these cases resulted from importations and
occurred almost exclusively in unvaccinated persons, the findings
underscore the ongoing risk for measles among unvaccinated persons
and the importance of maintaining high levels of vaccination.
Measles cases in the United States are reported by state health
departments preliminarily to CDC, and confirmed cases are reported
officially via the National Notifiable Disease Surveillance System,
using standard case definitions and case classifications. Cases are
considered importation associated if they are (1) acquired outside
the United States (i.e., international importation) or (2) acquired
inside the United States and either epidemiologically linked via a
chain of transmission to an importation or accompanied by virologic
evidence of importation (i.e., a chain of transmission from which a
measles virus is identified that is not endemic in the United
States). Other cases in the United States are classified as having
an unknown source.
During January 1-April 25, 2008, a total of 64 preliminary
confirmed measles cases were reported from the following areas: New
York City (22 cases), Arizona (15), California (12), Michigan and
Wisconsin (four each), Hawaii (three), and Illinois, New York
state, Pennsylvania, and Virginia (one each). Patients ranged in
age from 5 months to 71 years; 14 patients were aged <12 months, 18
were aged 1-4 years, 11 were aged 5-19 years, 18 were aged 20-49
years, and three were aged >=50 years, including one U.S. resident
born before 1957.
Fourteen (22%) patients were hospitalized; no deaths were reported.
Transmission occurred in both healthcare and community settings.
One of the 44 patients for whom transmission setting was known was
an unvaccinated healthcare worker who was infected in a hospital.
Seventeen (39%) were infected while visiting a healthcare facility,
including a child aged 12 months who was exposed in a physician's
office when receiving a routine dose of measles, mumps, and rubella
(MMR) vaccine.
Fifty-four (84%) of the 64 measles cases were importation
associated: 10 (16%) of the 64 were importations (five in visitors
to the United States and five in U.S. residents traveling abroad)
from Switzerland (three), Israel (three), Belgium (two), and India
and Italy (one each); 29 (45%) cases were epidemiologically linked
to importations; and 15 (23%) cases had virologic evidence of
importation. The remaining 10 (16%) cases were from unknown
sources; however, all occurred in communities with importation-associated cases. Specimens from 14 patients were genotyped at CDC,
and four different genotypes were identified: three from Arizona
(genotype D5), three from California (D5), five from New York City
(one in a case epidemiologically linked to an imported case from
Belgium and four in cases in communities where importations from
Israel had occurred; all D4), two from Wisconsin (H1), and one from
Michigan (D5).
Fifty-six of the 64 measles cases reported in 2008 have occurred in
five outbreaks (defined as three or more cases linked in time or
place). In New York City, an outbreak of 22 cases has been
reported, including four importations and 18 other cases (10
importation associated). In Arizona, 15 cases have been reported;
the index patient was an unvaccinated adult visitor from
Switzerland. In San Diego, California, 11 cases have been reported,
and an additional case spread to Hawaii; the index patient in the
San Diego outbreak was an unvaccinated child who had traveled to
Switzerland. In Michigan, four cases have been reported; the index
patient was an unvaccinated youth aged 13 years with an unknown
source of infection. In Wisconsin, four cases have been reported;
the index patient was a person aged 37 years with unknown
vaccination status who likely was exposed to a Chinese visitor with
measles-compatible illness.
Sixty-three of the 64 patients were unvaccinated or had unknown or
undocumented vaccination status, and one patient had documentation
of receiving 2 doses of MMR vaccine. None of the five patients who
were visitors to the United States had been vaccinated. Among the
59 patients who were U.S. residents, 13 were aged <12 months and
too young to be vaccinated routinely, seven were children aged 12-15 months and had not yet received vaccination, 21 were children
aged 16 months-19 years, including 14 (67%) who claimed exemptions
because of religious or personal beliefs. Among the 18 patients
aged >=20 years, 14 had unknown or undocumented vaccination status,
two had claimed exemptions and acquired measles in Europe, one had
evidence of immunity because of birth before 1957, and one had
documentation of receiving 2 doses of MMR vaccine.
Of the five U.S. residents with measles who were vaccine eligible
and had traveled abroad, all were unvaccinated. One was a child
aged 15 months who was not vaccinated before travel, and two were
adults who were unvaccinated because of personal belief exemptions.
For two adults, the reason for not being vaccinated was unknown.
Editorial Note:
Although ongoing measles transmission was declared eliminated in
the United States in 2000 and in the World Health Organization
(WHO) Region of the Americas in 2002, approximately 20 million
cases of measles occur each year worldwide. The 2008 upsurge in
measles cases serves as a reminder that measles is still imported
into the United States and can result in outbreaks unless
population immunity remains high through vaccination. Among the 64
confirmed measles cases, prior vaccination could be documented for
only one person.
Before introduction of measles vaccination in 1963, approximately 3
to 4 million persons had measles annually in the United States;
approximately 400-500 died, 48,000 were hospitalized, and 1,000
developed chronic disability from measles encephalitis. Even after
elimination of endemic transmission in 2000, imported measles has
continued to create a substantial U.S. public health burden; of the
501 measles cases reported during 2000-2007, one in four patients
was hospitalized, and one in 250 died.
Thus far in 2008, five U.S. residents and five visitors have been
documented as acquiring measles abroad. Of these 10 persons, nine
acquired measles in the WHO European Region. These importations
likely are related to an increase in 2008 in measles activity in
Europe. In Switzerland, approximately 2,250 measles cases have been
reported since November 2006. The Swiss measles outbreak started in
Lucerne, where the measles vaccination coverage level in children
is 78%, and spread across the country, predominantly affecting
children aged 5-15 years who were unvaccinated because of parental
opposition to vaccination. In Israel (which is included in the WHO
European Region), a measles outbreak with approximately 1,000 cases
is ongoing (Ministry of Health, Israel, unpublished data, 2008),
and measles transmission is occurring in other European countries,
predominantly among populations opposed to vaccination. This
situation prompted travel advisories to be issued in the United
States and Europe. Healthcare providers should advise patients who
travel abroad of the importance of measles vaccination and should
consider the diagnosis of measles in persons with clinically
compatible illness who have traveled abroad recently or have had
contact with travelers.
The limited size of recent measles outbreaks in the United States
has resulted from highly effective measles and MMR vaccines,
preexisting high vaccination coverage levels in preschool and
school-aged children, and a rapid and effective public health
response. All children should receive 2 doses of MMR vaccine, with
the first dose recommended at age 12-15 months and the second dose
at age 4-6 years. Unless they have other documented evidence of
measles immunity, all adults should receive at least 1 dose. Two
doses are recommended for international travelers aged >=12 months,
healthcare personnel, and students at secondary and postsecondary
educational facilities. Infants aged 6-11 months should receive 1
dose before travel abroad. During a measles outbreak, the
vaccination response should be guided by the epidemiology of the
outbreak and the outbreak setting and might include offering 1 dose
of measles or MMR vaccine to infants aged 6-11 months, offering the
second dose to preschool-aged children provided that 28 days have
elapsed since the first dose, and recommending 1 dose to healthcare
workers born before 1957 unless they show other evidence of
immunity.
Patients with measles frequently seek medical care, and emergency
departments are common sites of measles transmission. To prevent
transmission of measles in healthcare settings, patients should be
asked to wear a surgical mask (if tolerated) for source
containment, airborne infection-control precautions should be
followed stringently, and patients should be placed in a negative
air-pressure room as soon as possible. If a negative air-pressure
room is not available, the patient should be placed in a room with
the door closed. Measles cases should be investigated, patients
isolated promptly, and specimens obtained for laboratory
confirmation and viral genotyping. Case contacts without documented
evidence of measles immunity should be vaccinated, offered immune
globulin, or asked to quarantine themselves at home from the fifth
day after their first exposure to the twenty-first day after their
last exposure. Contacts with measles-compatible symptoms should be
managed in a manner that will prevent further spread.
Healthcare personnel place themselves and their patients at risk if
they are not protected against measles. In accordance with current
recommendations, healthcare personnel should have documented
evidence of measles immunity readily available at their work
location. If this documentation is not available when measles is
introduced, major costs and disruptions to healthcare operations
can result from the need to exclude potentially infected staff
members and rapidly ensure immunity for others.
Many of the measles cases in children in 2008 have occurred among
children whose parents claimed exemption from vaccination because
of religious or personal beliefs and in infants too young to be
vaccinated. Forty-eight states currently allow religious exemptions
to school vaccination requirements, and 21 states allow exemptions
based on personal beliefs. During 2002 and 2003, nonmedical
exemption rates were higher in states that easily granted
exemptions than states with medium or difficult exemption
processes; in such states, the process of claiming a nonmedical
exemption might require less effort than fulfilling vaccination
requirements.
Although national vaccination levels are high, unvaccinated
children tend to be clustered geographically or socially,
increasing their risk for outbreaks. An upward trend in the mean
proportion of school children who were not vaccinated because of
personal belief exemptions was observed from 1991 to 2004.
Increases in the proportion of persons declining vaccination for
themselves or their children might lead to large-scale outbreaks in
the United States, such as those that have occurred in other
countries (e.g., United Kingdom and Netherlands).
Ongoing measles virus transmission has been eliminated in the
United States, but the risk for imported disease and outbreaks
remains. High vaccination coverage in the United States has limited
the spread of imported measles in 2008. Nevertheless, the measles
outbreaks in 2008 illustrate the risk created by importation of
disease into clusters of persons with low vaccination rates, both
for the unvaccinated and those who come into contact with them.
To access a ready-to-print (PDF) version of the MMWR Early Release,
go to: http://www.cdc.gov/mmwr/PDF/wk/mm57e501.pdf
To access a web-text (HTML) version of the MMWR Early Release, go
to: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm57e501a1.htm
To access the transcript of the May 1 press briefing, go to:
http://www.cdc.gov/od/oc/media/transcripts/2008/t080501.htm
To access the related fact sheet, go to:
http://www.cdc.gov/od/oc/media/pressrel/2008/a080501Fact.htm
To access the Measles Update from the Features section of the CDC
homepage, go to: http://www.cdc.gov/Features/MeaslesUpdate
Back to top |
| |
|
|
