Issue
Number 559
October 18, 2005
CONTENTS OF THIS ISSUE
- Official CDC Health Advisory confirms a human rabies
death in Mississippi
- CDC releases report on recent poliovirus infections
among four unvaccinated children in Minnesota
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October 18, 2005
OFFICIAL CDC HEALTH ADVISORY CONFIRMS A HUMAN RABIES DEATH IN
MISSISSIPPI
On October 12, the Health Information Network (HAN) issued an Official CDC
Health Advisory, "Confirmation of Human Rabies Infection in Mississippi." It
is reprinted below in its entirety.
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This is an official CDC HEALTH ADVISORY
Distributed via Health Alert Network
Wednesday, October 12, 2005, 18:18 EDT (6:18PM EDT)
CONFIRMATION OF HUMAN RABIES INFECTION IN MISSISSIPPI
On October 5, 2005, the Centers for Disease Control and Prevention (CDC),
working together with the Mississippi Department of Health, confirmed a
diagnosis of rabies as the cause of death in a Mississippi child. This
advisory provides information about this case, an update for states that may
receive inquiries due to public concerns about rabies, and criteria for
conducting risk assessments as part of these investigations to determine the
need for post exposure prophylaxis (PEP).
The patient had been hospitalized with encephalitis of undetermined origin
in September 2005. No history of foreign travel or definitive animal
exposure was identified. A greater than fourfold rise in rabies virus
antibodies was demonstrated in both paired serum and cerebrospinal fluid
samples. No other clinical specimens were available to allow viral
characterization and identification of a likely animal source of infection.
Bats are the only known reservoirs of rabies in Mississippi, and the state
has reported no human cases since 1956. Although the child stayed at a
popular summer camp in Alabama and participated in an overnight caving event
in Tennessee during the summer, there were no known exposure incidents at
either venue. On additional investigation, it was reported that the child
removed a live bat from his bedroom in the spring of this year. The
Mississippi Department of Health, in conjunction with local medical staff
and CDC, conducted an investigation to identify contacts of the patient
among family, the local community, and healthcare workers. CDC will continue
to work with other state health departments and healthcare providers as
additional information becomes available.
Human rabies PEP is recommended only in situations in which potentially
infectious material (e.g., saliva) from a rabid animal or human is
introduced via a bite, or comes into direct contact with broken skin or
mucous membranes. In addition, when a bat is physically present and rabies
infection cannot be ruled out by testing the bat, human rabies PEP might be
appropriate if there is a reasonable probability that an exposure might have
occurred, such as when a bite cannot be excluded.
This is the first report of a human rabies case in the United States in
2005, and the 48th human case reported since 1990. Although human rabies is
extremely rare in the United States, people are advised to exercise caution
in settings where they might have contact with wildlife, especially bats,
raccoons, skunks, and foxes.
Camping and other outdoor activities do not present an elevated risk for
rabies exposure. Regardless of activity, people should avoid contact with
wildlife and stray animals.
Additional information about rabies and its prevention is available from the
Mississippi Department of Health, telephone (601) 576-7725 and at CDC,
telephone (404) 639-1050 or at
http://www.cdc.gov/ncidod/dvrd/rabies This website is updated as new
information becomes available.
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To access the advisory from the HAN archives, go to:
http://www.phppo.cdc.gov/HAN/ArchiveSys/ViewMsgV.asp?AlertNum=00239
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October 18, 2005
CDC RELEASES REPORT ON RECENT POLIOVIRUS INFECTIONS AMONG FOUR UNVACCINATED
CHILDREN IN MINNESOTA
CDC published "Poliovirus Infections in Four Unvaccinated
Children--Minnesota, August-October 2005" in the October 14 issue of "MMWR
Dispatch." CDC publishes the web-based "MMWR Dispatch" only for the
immediate release of important public health information. The article will
be published in the MMWR Weekly Report in the future. The article is
reprinted below in its entirety, excluding acknowledgments and references.
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On September 29, 2005, the Minnesota Department of Health (MDH) identified
poliovirus type 1 in an unvaccinated, immunocompromised infant girl aged 7
months (the index patient) in an Amish community whose members predominantly
were unvaccinated for polio. The patient has no paralysis; the source of the
patient's infection is unknown. Subsequently, poliovirus infections in three
other children within the index patient's community have been documented.
This report summarizes the ongoing investigation, provides information
regarding poliovirus exposure risks and prevention measures in the United
States, and offers recommendations to state health departments and
clinicians.
Index Case Summary
The index patient was first admitted to a community hospital in central
Minnesota for pneumonia in July 2005. Since August 22, this infant has been
hospitalized continuously at three additional hospitals with failure to
thrive, diarrhea, and recurrent infections. The infant was placed in strict
isolation, and a diagnosis of severe combined immunodeficiency (SCID) was
made on September 15. The infant is being clinically managed with
intravenous immunoglobulin therapy and is being evaluated for bone marrow
transplantation.
Laboratory Investigation
An enterovirus isolate from a stool specimen obtained on August 27, 2005,
tested positive for a type 1 poliovirus at the MDH laboratory. Partial
sequencing of the virus capsid protein coding region (VP1) of the poliovirus
genome at the MDH laboratory identified it as a vaccine-derived poliovirus (VDPV).
VDPVs are poliovirus strains derived from one of the three Sabin poliovirus
strains in oral polio vaccine (OPV) that have 1% [or greater] difference in
nucleotide sequence from the prototype vaccine virus. Additional sequencing
of the entire poliovirus genome at the CDC polio laboratory confirmed that
this strain was a VDPV, with 2.3% divergence in the VP1 region from the
parent Sabin type 1 strain. The viral genome demonstrates no recombination
with other polioviruses or species C enteroviruses. Prospective serial stool
samples from the infant are being tested to monitor ongoing infection and
further mutations in the virus.
Epidemiologic Investigation
Because viral genomic data suggest this poliovirus might have been
transmitted to the index patient from another immunocompromised person, the
initial investigation focused on identifying immunodeficient persons among
community contacts, healthcare workers, and patients with whom the infant
had potential contact before the first positive poliovirus culture on August
27. Staff and patient records at the hospitals are being reviewed, and
inquiries are being made with community members and healthcare providers.
Investigations also are under way at the four hospitals where the infant has
been treated to determine whether nosocomial transmission from the infant
has occurred. At the hospital where the infant currently is a patient,
healthcare workers and other staff members who have had exposure (without
protection from contact precautions) to the infant or the infant's
environment are being surveyed regarding polio vaccination status, immune
status, and recent relevant illnesses in themselves and their family
members. Stool samples are being obtained for viral cultures. Vaccination
with inactivated polio vaccine (IPV) is being offered to healthcare workers
who might have been exposed or who have an ongoing risk for exposure and
whose polio vaccination status is not up to date or is unknown. Stool
specimens also are being obtained from potentially exposed patients at the
hospital where the infant currently is a patient. At the first three
hospitals where the infant was admitted, healthcare workers are being
surveyed regarding immune status and recent illness in themselves or their
family members.
To examine community transmission of poliovirus, family members and others
in the index patient's community are being surveyed regarding polio
vaccination status, immune status, and recent illnesses. To date, stool
samples have been collected from 32 persons in five of 24 households, and
serum samples have been obtained from eight persons in three households,
including the index patient's household. Poliovirus type 1 has been
confirmed in three of 32 stool specimens; partial sequencing of the VP1
region of these three isolates has indicated they also are VDPV type 1. The
positive specimens were obtained from three unvaccinated siblings in one
household (not the infant's household). None of these three children have
been ill recently, and none were immunocompromised. Stool and serum samples
are being requested from additional members of the community. Extended
family members and community contacts from other areas who might have come
into contact with the index patient are being identified and monitored for
illness. IPV is being offered to community members who are not fully
vaccinated for polio or whose polio vaccination status is unknown. Hospitals
that serve this community and similar communities are being contacted, and
retrospective and prospective surveillance is identifying patients whose
diagnoses indicate conditions that are clinically consistent with poliovirus
infection, including acute flaccid paralysis (AFP), Guillain-Barré Syndrome
(GBS), transverse myelitis, and viral or aseptic meningitis.
Editorial Note
The findings in this report are the first identification of a VDPV in the
United States and the first occurrence of VDPV transmission in a community
since OPV vaccinations were discontinued in 2000. The extent of circulation
within the affected community is not yet known. However, the identification
of poliovirus infection in the index patient and three other unvaccinated
children in a community at high risk for poliovirus transmission raises
concerns regarding (1) transmission to other communities with low levels of
vaccination and (2) the risk for a polio outbreak occurring in the United
States. Potential also exists for transmission of this virus to other
immunodeficient persons. Although this VDPV has not been associated with
paralytic disease, based on previous experience with VDPVs, the virus is
considered to have potential both for wider transmission and for causing
paralytic disease.
VDPVs emerge from OPV viruses as a result of (1) their continuous
replication in immunodeficient persons (immunodeficiency-associated or
iVDPVs) such as the index patient in this investigation or (2) their
circulation in populations with low vaccination coverage (circulating or
cVDPVs). During community circulation, cVDPVs often recombine with other
species C enteroviruses, which is not characteristic for iVDPVs. Because
polioviruses accumulate nucleotide changes at a constant rate of mutation
(approximately 1% per year), the time of replication can be inferred from
the degree of divergence. Because cVDPVs commonly revert to a wild
poliovirus phenotype, they can have increased transmissibility and high risk
for paralytic disease; cVDPVs have caused outbreaks of poliomyelitis in
several countries. VDPVs in highly immunized populations are rare. Before
the VDPV identification in Minnesota, the most recent known VDPV excreter in
the United States was a child with SCID (now deceased) who developed
vaccine-associated paralytic poliomyelitis in 1995.
Given the degree of difference (2.3%) from the parent Sabin poliovirus type
1 strain, the virus isolated from the index patient is estimated to have
been replicating for approximately 2 years, which means the virus likely is
older than the infant. OPV is still widely used in most countries; however,
because OPV has not been used in the United States since 2000 and in Canada
since 1997, the original source of this virus likely was a person who
received OPV in another country. Neither the infant nor her family members
had any history of international travel. This virus is not related to other
known iVDPVs or to any type 1 cVDPVs that caused outbreaks such as those in
Hispaniola during 2000-2001, the Philippines during 2001, or Indonesia
during 2005.
Most poliovirus infections are asymptomatic or cause mild, febrile disease.
Poliovirus infections occasionally cause aseptic meningitis and one out of
200 infections from poliovirus type 1 results in paralytic poliomyelitis,
characterized by acute onset of flaccid paralysis that is typically
asymmetric and associated with a prodromal fever. Poliovirus is spread
through fecal material, oral secretions, and fomites. Widespread
transmission among vaccinated healthcare workers or in a community with high
vaccination coverage is unlikely because fully vaccinated persons are not at
risk for disease from this or other polioviruses and seldom shed the virus
for longer than a week if they are infected. The National Immunization
Survey reports that polio vaccination coverage in Minnesota is 93% for
children aged 19-35 months and 98% for school-aged children; however,
communities of unvaccinated persons exist in Minnesota and many other
states. The risk for transmission in communities with low vaccination
coverage is high. The estimated rate of transmission for wild poliovirus
among unvaccinated household contacts is 73%-96%. Contacts between persons
in communities with low vaccination coverage pose the potential for
transmission of this poliovirus to other communities in the United States,
Canada, and other countries.
The last wild poliovirus outbreak in the United States occurred in 1979 and
was caused by a wild type 1 poliovirus. In that outbreak, 10 paralytic
poliomyelitis cases and four other poliovirus infections occurred among
unvaccinated Amish persons and members of other religious communities with
low levels of vaccination who lived in Iowa, Missouri, Pennsylvania, and
Wisconsin. The source of this outbreak was traced to religious groups in
Canada and the Netherlands that also had low levels of vaccination. A polio
outbreak in 1993 in the Netherlands with 71 paralytic cases among members of
unvaccinated religious communities also resulted in poliovirus transmission
without paralytic disease in Alberta, Canada; no evidence of transmission
from this outbreak was found in the United States.
Persons in communities with low vaccination coverage should be warned of the
potential risk for poliomyelitis. States with large communities with low
vaccination coverage should identify these communities, assess their current
vaccination status, and offer IPV. These states also should establish
enhanced or active surveillance for AFP, GBS, and transverse myelitis.
Physicians should be aware of and vigilant for poliomyelitis and other
causes of AFP in patients. Stool samples, throat swabs, cerebrospinal fluid,
and serum should be collected for viral culture and serology from these
patients. With evidence of transmission in Minnesota, serologic and/or stool
surveys to detect poliovirus type 1 circulation in affiliated communities
with low levels of vaccination also should be considered.
IPV, the polio vaccine currently used in the United States, provides
immunity against this vaccine-derived poliovirus strain. The Advisory
Committee on Immunization Practices (ACIP) recommends that a full 3-dose IPV
series be administered on an accelerated schedule if polio immunization
status is unknown or not documented. A booster dose of IPV is recommended
for adults in susceptible communities and healthcare workers at high risk
for exposure who have completed a primary series but have not received an
adult booster dose.
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