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March
2007: VOLUME
1, NUMBER 5
The
2006/2007 Influenza Season: An Epidemiologic Snapshot
In this issue...
Over
the past year, both the general press and the medical establishment
have expressed concerns about the 2006/2007 influenza season. While
fears of a potential avian flu pandemic have captured most of the headlines,
other, more immediate, questions have been asked, including:
- How
virulent has this year's seasonal influenza virus been?
- How
closely have the components of the influenza vaccine matched the
affecting strains?
- Has
this season shown an increased or decreased morbidity and mortality
in the higher-risk groups, particularly in children?
In
this issue – in a departure from our usual format – we review
the data provided by the CDC to present an epidemiologic "snapshot" at
week 10 of the 2006/2007 influenza season. |
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GUEST
EDITOR OF THE MONTH |
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Commentary
& Reviews:
Michael
L. Tapper, MD
Hospital Epidemiologist
Director, Division of Infectious Diseases
Lenox Hill Hospital
New York, New York
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Guest
Faculty Disclosure
Michael
L. Tapper, MD, has no relationship with commercial supporters.
Unlabeled / Unapproved Uses
The author has indicated that there will be no reference
to unlabeled/ unapproved uses of drugs or products in this presentation. |
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LEARNING
OBJECTIVES |
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The
Johns Hopkins University School of Medicine and The Institute for
Johns Hopkins Nursing take responsibility for the content, quality,
and the scientific integrity of this CE activity.
At the conclusion of this activity, participants should be
able to: |
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Identify
the primary influenza viruses currently circulating in the US |
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Compare
the primary circulating influenza viruses with the 2006/2007 influenza
vaccine components |
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Discuss
the reported morbidity and mortality attributed to influenza thus
far this season |
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COMPLETE
THE POST TEST
Step 1.
Click on the appropriate link
below. This will take you to the post-test.
Step 2.
If you have participated in a
Johns Hopkins on-line course, login. Otherwise, please register.
Step 3.
Complete the post-test and course
evaluation.
Step 4.
Print out your certificate.
Pharmacy credit is only available via PDF mail-in form:
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SURVEILLANCE
OVERVIEW |
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The
Influenza Branch at the CDC collects and reports information on influenza
activity in the United States each week from October through May. The
U.S. influenza surveillance system has seven components, which together
are designed to provide a national picture of influenza activity. Data
is collected from:
- The
U.S. World Health Organization (WHO) and National Respiratory and
Enteric Virus Surveillance System (NREVSS) Collaborating Laboratories:
These 130 laboratories, located throughout the United States report
the total number of respiratory specimens tested and the number confirmed
positive for influenza types A and B each week.
- The
U.S. Influenza Sentinel Providers Surveillance Network: Each week,
approximately 1,200 healthcare providers around the country voluntarily
report the total number of patients seen and the number of those
patients with influenza-like illness (ILI), defined as fever of >-100oF
and a cough and/or sore throat in the absence of a known cause other
than influenza.
- The
122 Cities Mortality Reporting System: Weekly, the Vital Statistics
Offices of 122 cities around the country report the number of death
certificates received for which pneumonia or influenza was listed
as the underlying or contributing cause of death. The percentage
of all deaths due to pneumonia and influenza are compared with a
seasonal baseline, and an epidemic threshold value is calculated
for each week.
- State
and Territorial Epidemiologists Reports: State health departments
report the estimated level of influenza activity in their states
each week.
- Influenza-associated
pediatric mortality: This newly added component reports laboratory-confirmed
influenza-associated deaths in children less than 18 years old, and
reports through the Nationally Notifiable Disease Surveillance System.
- Emerging
Infections Program (EIP): This component reports every two weeks
during the influenza season on laboratory-confirmed influenza-related
hospitalizations in persons less than 18 years of age in 60 counties,
covering 12 metropolitan areas in 10 states.
- The
New Vaccine Surveillance Network (NVSN): This network provides bi-weekly
population-based estimates of laboratory-confirmed influenza hospitalization
rates for children less than 5 years old residing in three counties
(in Ohio, Tennessee, and New York).
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CURRENTLY
CIRCULATING INFLUENZA VIRUSES |
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Since
October 1, 2006, U.S. laboratories reporting to the CDC have tested
a total of 128,223 specimens for influenza viruses, with 16,602
(12.9%) found positive. Antigenic characteristics have been determined
for 325 influenza viruses: to date, about two-thirds (200) have
been H1N1, and a relatively small number (25) have been the more
severe H3N2 subtype. The (100) remaining viruses have been influenza
B, which is generally considered a less severe human pathogen.
A graphic summary
of these data, collected by U.S. World Health Organization (WHO)
and National Respiratory and Enteric Virus Surveillance System (NREVSS)
laboratories, appears below:
During
week 10 of this current flu season, the WHO and NREVSS laboratories
reported 4,417 specimens tested for influenza viruses, 830 (18.8%)
of which were positive: 86 influenza A (H1) viruses, 29 influenza
A (H3) viruses, 448 influenza A viruses that were not subtyped, and
267 influenza B viruses.
If the predominating
circulating virus remains H1N1, it appears the U.S. is on track for
a relatively mild flu season that falls within (or below) normal
seasonal variation. |
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CIRCULATING
VIRUS AND THE 2006/2007 VACCINE |
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Further
reinforcing this indication of a mild influenza season is the match
of the 2006-07 influenza vaccine to the currently circulating viruses.
The CDC reports:
- 189
(95%) of the 200 H1 viruses characterized were similar to A/New Caledonia/20/99-like,
which is the influenza A (H1) component of the 2006-07 influenza
vaccine.
- 11
(5%) of the 200 viruses showed somewhat reduced titers with antisera
produced against A/New Caledonia/20/99 and are similar to A/Solomon
Islands/3/2006-like.
- 12
(48%) of the 25 H3 viruses were characterized as A/Wisconsin/67/2005-like,
which is the influenza A (H3) component of the 2006-07 influenza
vaccine.
- 13
(52%) of the 25 H3 viruses showed somewhat reduced titers with antisera
produced against A/Wisconsin/67/2005.
- 71
(71%) of the 100 influenza B viruses characterized belong to the
B/Victoria lineage of viruses.
- 42
(59%) of these 71 viruses were similar to B/Ohio/01/2005, the B component
of the 2006-07 influenza vaccine.
- 29
(41%) of these 71 viruses showed somewhat reduced titers with antisera
produced against B/Ohio/01/2005.
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U.S.
EPIDEMIOLOGY |
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Low
levels of flu activity were reported in the United States during October
through early December. Flu activity increased from mid-December through
the end of the year, declined slightly in early January, and then increased
again in mid-January.
During week 10 (ending 10 March
2007) of the current influenza season, the following influenza activity
was reported by state and territorial epidemiologists:
- Widespread
activity was reported by 19 states (Alabama, Alaska, Colorado, Connecticut,
Delaware, Georgia, Indiana, Kentucky, Montana, New Jersey, New York,
North Carolina, Ohio, Oklahoma, Pennsylvania, Texas, Vermont, Virginia,
and Washington).
- Regional
activity was reported by 23 states (Arizona, Arkansas, California,
Hawaii, Idaho, Illinois, Iowa, Kansas, Maine, Massachusetts, Michigan,
Minnesota, Nevada, New Hampshire, New Mexico, North Dakota, Oregon,
South Carolina, South Dakota, Tennessee, Utah, Wisconsin, and Wyoming).
- Local
activity was reported by New York City, the District of Columbia,
and four states (Florida, Louisiana, Maryland, and Mississippi).
- Sporadic
activity was reported by three states (Missouri, Rhode Island, and
West Virginia).
- No
report was received from Nebraska.
To
present these data in graphic form:
It
should be noted that these categories (local, regional, widespread,
etc) are less than adequately informed by specific incidence rates.
The current definitions are based on reported Influenza-Like Illness
(ILI) cases:
- No
Activity: No laboratory-confirmed cases of influenza and no reported
increase in the number of cases of ILI.
- Sporadic:
Small numbers of laboratory-confirmed influenza cases or a single
laboratory-confirmed influenza outbreak has been reported, but there
is no increase in cases of ILI.
- Local:
Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed
influenza in a single region of the state.
- Regional:
Outbreaks of influenza or increases in ILI and recent laboratory
confirmed influenza in at least 2 but less than half the regions
of the state.
- Widespread:
Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed
influenza in at least half the regions of the state.
Although
updated a few years ago with input from the Council of State and Territorial
Epidemiologists (CSTE), these definitions are widely recognized as the
weakest part of the national influenza surveillance system. Last fall,
the CDC convened a workgroup to begin discussing and updating these
category definitions. |
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SEVERITY |
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The
overall severity of a flu season (measured by infections, hospitalizations
and deaths) is determined by comparing the following criteria against
measurements taken during previous seasons:
- The
number of states that are affected by flu and the degree to which
they are affected;
- The
proportion of laboratory tests that are positive for flu;
- The
proportion of all deaths that are caused by pneumonia and flu;
- The
number of flu-associated deaths among children;
- The
rate of flu hospitalization for children.
One
of the key elements in determining the proportion of deaths caused by
pneumonia and flu is the P & I, or Pneumonia & Influenza Mortality Surveillance.
Based on death certificates with the cause of death listed as either
pneumonia or influenza, these data are reported by local and state health
departments.
The
graphic shows flu-related mortality for the past several years, with
reference to a normal seasonal baseline (reflecting the fact that there
are increased deaths that normally occur during the winter due to a
variety of viruses other than influenza) and to a threshold above which
the percentage of deaths would be considered epidemic. As can readily
be seen, compared to previous years (particularly the 2003/2004 season),
this current flu season thus far appears to be relatively mild.
Specifically, during week 10,
7.2% of all deaths were reported as due to pneumonia or influenza, a
percentage below the epidemic threshold of 7.9%.
Children are one of the primary
risk groups for influenza and its complications, and the CDC collects
specific data on influenza-associated pediatric hospitalizations and
mortality. Laboratory-confirmed influenza-associated pediatric hospitalizations
are monitored by two population-based surveillance networks: the Emerging
Infections Program (EIP) and the New Vaccine Surveillance Network (NVSN).
During October 1, 2006 – March 3, 2007, the EIP reported the preliminary
laboratory-confirmed influenza-associated hospitalization rate for children
aged 0-4 years as 1.27 per 10,000; for children aged 5-17 years, the
rate was 0.18 per 10,000. The NVSN reported that during November 5,
2006 – March 3, 2007, the preliminary laboratory-confirmed influenza-associated
hospitalization rate for children aged 0-4 years old was 1.62 per 10,000.
These data, with comparisons
to recent flu seasons, are represented graphically as:
Regarding
pediatric mortality, the CDC shows that 7 influenza-associated pediatric
deaths were reported during week 10. Since October 1, 2006, the CDC
has received 32 reports of influenza-associated pediatric deaths that
have occurred during the 2006/2007 season. Unfortunately, more flu-associated
deaths may occur among children as the season progresses; however, at
this time, neither childhood deaths nor hospitalizations are greater
than expected for this point in the season.
In comparison to previous years:
- During
the 2005/2006 season, 44 flu-associated deaths in children under
age 18 were reported to CDC.
- During
the 2004/2005 season, 48 flu-associated deaths in children were reported.
- During
the 2003/2004 season, 153 flu-associated deaths in children were
reported.
An
additional form of surveillance used to determine the severity of a
flu season is the Sentinel Provider Network, where state and local health
departments ask various health-care providers (particularly physicians
in general practice) to voluntarily report the number of Influenza-Like
Illnesses (ILI) they are seeing in their practices. This network of
family physicians and internists, etc are most likely the first to diagnose
influenza in their patients, and their data – reflecting those
cases that normally do not require hospitalization – both add
to the CDC's ability to provide an overall picture of flu activity,
and also serve as an "early warning system" to make health care providers
(including hospital-based physicians and public health officials) aware
of increasing influenza outbreaks in their local communities.
During week 10 of the 2006/2007
influenza season, 2.7% of patient visits to U.S. Sentinel Providers
were due to ILI, above the national baseline of 2.1%.
Presented graphically, the data
for this and the previous 2 influenza seasons is as follows:
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COMPOSITION
OF THE 2007/2008 INFLUENZA VACCINE |
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Based
on antigenic analyses of recently isolated influenza viruses, epidemiologic
data, and post-vaccination serologic studies in humans, WHO has recommended
that the 2007/2008 trivalent influenza vaccine for the Northern Hemisphere
contain the following:
- A/Solomon
Islands/3/2006-like (H1N1) - a recent antigenic variant of the current
vaccine strain A/New Caledonia/20/99.
- A/Wisconsin/67/2005-like
(H3N2).
- B/Malaysia/2506/2004-like
viruses (antigenically equivalent to B/Ohio/1/2005).
The
influenza A (H1N1) component has been changed from the 2006/2007 season
vaccine components, while the influenza A (H3N2) and influenza B components
remain the same. |
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VACCINE & ANTIVIRALS |
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Although
vaccine production was adequate for this influenza season, there were
distribution problems in the fall of 2006 that resulted in shortages
and late deliveries to many clinics and private practices. Although
the CDC does not take an active role in vaccine distribution, physicians,
particularly those in private practice, are urged to place their vaccine
orders early on, and to secure alternative sources should these distribution
problems recur as the 2007/2008 season approaches.
Regarding antivirals: While no
direct studies have been published
reporting on the efficacy of
the neuraminidase inhibitors
this season, the CDC reports
that the H1N1 samples tested
in their labs have shown no developing
resistance to these agents. Historically,
H1N1 isolates have remained sensitive
to the M2 inhibitors (amantadine/rimantadine).
Further, in a recent
study in Japan reported in the NEJM (Letter to
the Editor, 18 January 2007), none of 61 isolates of H1N1 were resistant
to the adamantanes, in contrast to 65% of the H3N2 isolates. However,
the CDC continues to recommend that adamantanes not be used for treatment
or prophylaxis of seasonal flu, because of resistance in both influenza
A H3N2 and influenza B viruses. |
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SUMMARY |
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The
CDC's Influenza Branch cross-references a variety of data sources to
provide a continually evolving picture of influenza activity in this
country. During week 10 (March 4 – March 10, 2007), influenza
activity continued to decrease, declining for the fourth consecutive
week. While ILI data was above baseline for the twelfth week this season,
it too is declining, and the percent of deaths due to pneumonia and
influenza remained below baseline level.
The current influenza season
appears to be relatively mild,
due to both a prevalence of the
less severe H1N1 strain (versus
H3N2) and a superior match to
the components of the 2006/2007
vaccine. Further, influenza-associated
morbidity and mortality are within
(or below) expectations for this
point in the season.
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Further
information, as well as future weekly updates,
may be accessed via
the CDC's website at: CDC's
website. |
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CME/CNE/CPE
INFORMATION |
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| Accreditation
Statement — back
to top |
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This
activity has been planned and implemented in accordance with the
Essential Areas and Policies of the Accreditation Council for Continuing
Medical Education through the joint sponsorship of the Johns Hopkins
University School of Medicine and The Institute for Johns Hopkins
Nursing. The Johns Hopkins University School of Medicine is accredited
by the ACCME to provide continuing medial educaiton for physicians.
The Institute for
Johns Hopkins Nursing is accredited as a provider of continuing nursing
education by the American Nursing Credentialing Center's Commission
on Accreditation. |
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| Credit
Designations — back
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Physicians
The Johns Hopkins
University School of Medicine designates this educational activity
for a maximum of 1.0 AMA PRA Category 1 Credit(s)TM.
Physicians should only claim credit commensurate with the extent
of their participation in the activity.
Nurses
This 1.2 contact
hour Educational Activity (Provider Directed/Learner Paced) is provided
by The Institute for Johns Hopkins Nursing. Each Newsletter carries
a maximum of 1.2 contact hours or a total of 7.2 contact hours for
the six newsletters in this program.
Pharmacists
 This
program is approved for two hour credit (0.2 CEUs) and is co-sponsored
by the University of Tennessee College of Pharmacy who is approved
by the Accreditation Council for Pharmacy Education as a provider
of continuing pharmacy education. A statement of CE credit will be
mailed within 4 weeks of successful completion and evaluation of
the program. ACPE Program #064-999-06-274-H01.
Grievance Policy: A participant, sponsor, faculty
member or other individual wanting to file a grievance with respect
to any aspect of a program sponsored or co-sponsored by the UTCOP
may contact the Associate Dean for Continuing Education in writing.
The grievance will be reviewed and a response will be returned within
45 days of receiving the written statement. If not satisfied, an
appeal to the Dean of the College of Pharmacy can be made for a second
level of review. |
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take the post-test for eInfluenza Review you will need to visit The
Johns Hopkins University School of Medicine's CME website or The
Institute for Johns Hopkins Nursing. If you have already registered
for another Hopkins CME program at these sites, simply enter the
requested information when prompted. Otherwise, complete the registration
form to begin the testing process. A passing grade of 70% or higher
on the post test/evaluation is required to receive CME/CNE/CPE credit. |
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| Statement
of Responsibility — back
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Johns Hopkins University School of Medicine and The Institute for
Johns Hopkins Nursing take responsibility for the content, quality,
and scientific integrity of this CME/CNE/CPE activity. |
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Audience — back
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activity has been developed for the Primary Care Physician, Internist,
Infectious Disease Specialists and Nurse. There are no fees or prerequisites
for this activity. |
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| Learning
Objectives — back
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The
Johns Hopkins University School of Medicine and The Institute
for Johns Hopkins Nursing take responsibility for the content,
quality, and the scientific integrity of this CE activity.
At the
conclusion of this activity, participants should be able to: |
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Identify
the primary influenza viruses currently circulating in the US |
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Compare
the primary circulating influenza viruses with the 2006/2007
influenza vaccine components |
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Discuss
the reported morbidity and mortality attributed to influenza
thus far this season |
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| Internet
CME/CNE/CPE Policy — back
to top |
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The
Offices of Continuing Education (CE) at The Johns Hopkins University
School of Medicine and The Institute for Johns Hopkins Nursing are
committed to protect the privacy of its members and customers. The
Johns Hopkins University maintains its Internet site as an information
resource and service for physicians, other health professionals
and the public.
The Johns Hopkins
University School of Medicine and The Institute for Johns Hopkins
Nursing will keep your personal and credit information confidential
when you participate in a CE Internet based program. Your information
will never be given to anyone outside The Johns Hopkins University
program. CE collects only the information necessary to provide you
with the service you request. |
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Disclosure — back
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It
is the policy of The Johns Hopkins University School of Medicine
and The Institute for Johns Hopkins Nursing that the faculty and
provider disclose real or apparent conflicts of interest relating
to the topics of this educational activity, and also disclose discussions
of unlabeled/unapproved uses of drugs or devices during their presentation(s).
Johns Hopkins School of Medicine OCME and The Institute for Johns
Hopkins Nursing has established policies in place that will identify
and resolve all conflicts of interest prior to this educational
activity. Detailed disclosures will be made in the course handout
materials.
The presenting faculty
reported the following:
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John
G. Bartlett, MD, has disclosed that he has served on the HIV
Advisory Board for Glaxo Smith Kline, Abbott and Bristol-Myers
Squibb. |
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Jason
E. Farley, PhD(c), MPH, NP has disclosed that he has no relationship
with commercial supporters. |
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| Disclaimer
Statement — back
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opinions and recommendations expressed by faculty and other experts
whose input is included in this program are their own. This enduring
material is produced for educational purposes only. Use of Johns
Hopkins University School of Medicine name implies review of educational
format design and approach. Please review the complete prescribing
information of specific drugs or combination of drugs, including
indications, contraindications, warnings and adverse effects before
administering pharmacologic therapy to patients. |
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COMPLETE
THE POST TEST
Step 1.
Click on the appropriate link below. This
will take you to the post-test.
Step 2.
If you have participated in a Johns Hopkins
on-line course, login. Otherwise, please register.
Step 3.
Complete the post-test and course evaluation.
Step 4.
Print out your certificate.
Pharmacy credit is only available via PDF mail-in form:
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Copyright
© JHUSOM, IJHN, and eInfluenza Review
Created by DKBmed. |
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Johns Hopkins University School
of Medicine CME/CNE/CPE Office
720 Rutland Avenue, Baltimore,
MD 21205-2196 |
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