Published Date: 2011-12-08 17:27:33
Subject: PRO/EDR> Influenza (75): USA update
Archive Number: 20111208.3553
INFLUENZA (75): USA UPDATE
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A ProMED-mail post
http://www.promedmail.orgProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.orgDate: Fri 9 Dec 2011Source: MMWR Weekly, 2011 / 60(48);1646-1649 [abbreviated, edited]
http://www.cdc.gov/mmwr/preview/mmwrhtm ... ovdeliveryUpdate: influenza activity -- United States, 2 Oct to 26 Nov 2011
-------------------------------------------
During the period 2 Oct to 26 Dec 2011, influenza activity remained
low in the United States. Thus far, influenza A viruses have
predominated, and the majority are antigenically related to the
2011-12 influenza vaccine strains for the Northern Hemisphere. This
report summarizes US influenza activity* since 2 Oct 2011 and updates
the previous summary (1).
Viral surveillance
------------------
During the period 2 Oct to 26 Dec 2011, the World Health Organization
(WHO) and the National Respiratory and Enteric Virus Surveillance
System collaborating laboratories in the United States tested 24 027
respiratory specimens for influenza viruses; 266 (1.1 per cent) were
positive. Of these, 191 (71.8 per cent) were influenza A viruses, and
75 (28.2 per cent) were influenza B viruses. Of the 191 influenza A
viruses, 87 (45.5 per cent) were subtyped; 79 (90.8 per cent) were
influenza A (H3) viruses, and 8 (9.1 per cent) were 2009 influenza A
(H1) viruses. Influenza viruses have been reported from 30 states in
all 10 US Department of Health and Human Services (HHS) regions. Of
the 266 influenza-positive specimens reported to CDC so far this
season, 131 [49.2 per cent]) have been reported from the south eastern
United States.
Antigenic characterization
--------------------------
WHO collaborating laboratories in the United States are requested to
submit a subset of their influenza-positive specimens to CDC for
further antigenic characterization. CDC has antigenically
characterized 21 influenza viruses collected and submitted by US
laboratories since 1 Oct 2011, including one 2009 influenza A (H1N1),
16 influenza A (H3N2), and 4 influenza B viruses. The one 2009
influenza A (H1N1) virus was characterized as
A/California/7/2009-like, the influenza A (H1N1) component of the
2011-12 influenza vaccine for the Northern Hemisphere. All 16
influenza A (H3N2) viruses were antigenically related to the
A/Perth/16/2009, the influenza A (H3N2) component included in the
2011-12 influenza vaccine for the Northern Hemisphere. Three of the 4
influenza B viruses tested belong to the B/Victoria lineage and were
characterized as B/Brisbane/60/2008-like, the influenza B component of
the 2011-12 influenza vaccine for the Northern Hemisphere; one of the
4 B viruses tested belongs to the B/Yamagata lineage of viruses.
Antiviral resistance of influenza virus isolates
------------------------------------------------
CDC conducts surveillance for resistance of circulating influenza
viruses to influenza antiviral medications. Since 1 Oct 2011, a total
of 31 influenza viruses (5 2009 influenza A (H1N1), 24 influenza A
(H3N2), and 2 influenza B viruses) have been tested for antiviral
resistance. None of the tested viruses were found to be resistant to
either oseltamivir or zanamivir.
Novel influenza A viruses
-------------------------
Since the last influenza activity update (1), 6 cases of human
infection with a novel influenza A virus were reported: 2 from Maine
and one from Indiana in October 2011 (2), as well as 3 from Iowa in
November 2011. All 6 patients were infected with novel influenza A
(H3N2) viruses with genes from swine, human, and avian lineages. The 2
cases in Maine occurred in children, and the case in Indiana occurred
in an adult male; all patients had exposure to swine in the period
immediately preceding their illness. All 3 cases in Iowa occurred in
children with no known recent exposure to swine. The investigation in
Iowa revealed evidence of limited human-to-human transmission (2). All
patients recovered fully.
State-specific activity levels
------------------------------
For the week ending 26 Nov 2011, the geographic spread of influenza
was reported as local by one state (Massachusetts). Sporadic influenza
activity was reported by the District of Columbia (DC), Guam, and 28
states. The US Virgin Islands and 21 states reported no influenza
activity. Puerto Rico did not report. No states have reported
geographically regional or widespread influenza activity to date for
the 2011-12 influenza season.
Outpatient influenza-like illness
---------------------------------
Since 2 Oct 2011, the weekly percentage of outpatient visits for
influenza-like illness (ILI) reported each week by the approximately
1500 US Outpatient Influenza-Like Illness Surveillance Network
(ILINet) reporters in 50 states, New York City, Chicago, and DC has
remained below the national baseline of 2.4 per cent. None of the
regions have been above their region-specific baselines. Data
collected in ILINet also are used to produce a measure of ILI activity
by state. During the week ending 26 Nov 2011, all 50 states and New
York City experienced minimal ILI activity. Data were insufficient to
calculate an ILI activity level from DC.
Pneumonia- and influenza-related mortality
------------------------------------------
For the week ending 26 Nov 2011, pneumonia and influenza (P&I) was
reported as an underlying or contributing cause of death for 6.4 per
cent of all deaths reported to the 122 Cities Mortality Reporting
System. This percentage is below the epidemic threshold of 7.1 per
cent for that week. Since 2 Oct 2011, the weekly percentage of deaths
attributed to pneumonia and influenza ranged from 5.9 per cent to 6.4
per cent, remaining below the epidemic threshold.
Influenza-related pediatric mortality
-------------------------------------
No influenza-related pediatric deaths have been reported through the
Influenza Associated Pediatric Mortality Surveillance System for the
2011-12 influenza season.
MMWR editorial note
-------------------
Since 2 Oct 2011, surveillance data have indicated that influenza is
circulating at low levels in the United States; low activity typically
is noted in this early portion of the influenza season. Antigenic
characterization of the viral isolates that have been submitted
demonstrated that the majority of these isolates are antigenically
similar to the influenza virus strains in the Northern Hemisphere
2011-12 vaccine.
Influenza vaccination is the best method for preventing influenza and
its associated complications. Influenza vaccination currently is
recommended for all persons aged 6 months and over (3). Vaccine
manufacturers had distributed approximately 129.2 million doses of
influenza vaccine in the United States as of 25 Nov 2011 (4).
Influenza vaccination should continue to be offered by health-care
providers throughout the influenza season for all persons without
contraindications to vaccination to provide protection for as many
persons as possible. Multiple influenza vaccines are approved for use
and are being distributed during the 2011-12 season, including
trivalent inactivated vaccine (TIV) for persons aged 6 months or
older; live, attenuated influenza vaccine (LAIV) for nonpregnant,
otherwise healthy persons aged 2-49 years; a high-dose inactivated
vaccine for persons aged 65 years and older; and a new, intradermally
administered vaccine, which was licensed by the Food and Drug
Administration on 10 May 2011, for adults aged 18-64 years (3).
Children aged 6 months to 8 years who did not receive 2 doses of the
2010-11 seasonal influenza vaccine should receive 2 doses
(administered at least 4 weeks apart) of the 2011-12 seasonal
influenza vaccine (3).
Transmission of swine-origin influenza A viruses to humans is rare and
usually occurs among persons in direct contact with swine or among
persons who have visited places where swine are present (e.g.,
agricultural fairs, farms, and petting zoos). Clinicians should
consider swine-origin influenza A virus infection as well as seasonal
influenza virus infections in the differential diagnosis of patients
with febrile respiratory illness who have been near swine (8).
Clinicians who suspect influenza virus infection in patients with
recent exposure to swine should obtain a nasopharyngeal swab from the
patient, place the swab in a viral transport medium, and contact their
state or local health department to facilitate transport and timely
diagnosis at a state public health laboratory. Public health
laboratories are requested to submit any suspected swine-origin
influenza A samples to CDC for further testing. Early identification
and prompt investigation of novel influenza A cases are critical to
evaluating the extent of outbreaks and possible human-to-human
transmission.
References
----------
[1] CDC. Update: influenza activity--United States, 22 May-3 Sep 2011.
MMWR 2011;60:1239-42.
[2] CDC. Limited human-to-human transmission of novel influenza A
(H3N2) virus--Iowa, November 2011. MMWR 60:1615-7.
[3] CDC. Prevention and control of influenza with vaccines:
recommendations of the Advisory Committee on Immunization Practices
(ACIP), 2011. MMWR 2011;60:1128-32.
[4] CDC. Seasonal influenza vaccine--total doses distributed. Atlanta,
GA: US Department of Health and Human Services, CDC; 2011. Available
at
http://www.cdc.gov/flu/professionals/va ... supply.htm.
Accessed 2 Dec 2011.
[5] CDC. Antiviral agents for the treatment and chemoprophylaxis of
influenza--recommendations of the Advisory Committee on Immunization
Practices (ACIP). MMWR 2011;60(No.RR-1).
[6] Siston AM, Rasmussen SA, Honein MA, et al. Pandemic 2009 influenza
A (H1N1) virus illness among pregnant women in the United States. JAMA
2010;303:1517-25.
[7] Yu H, Feng Z, Uyeki T, et al. Risk factors for severe illness with
2009 pandemic influenza A (H1N1) virus infection in China. Clin Infect
Dis 2011; 52:457-65.
[8] CDC. Swine-origin influenza A (H3N2) virus infection in two
children--Indiana and Pennsylvania, July-August 2011. MMWR
2011;60:1213-5.
--
communicated by:
ProMED-mail
[The United States has continued to experience low levels of influenza
activity, and influenza A (H3N2), 2009 influenza A (H1N1), and
influenza B viruses have been identified sporadically. The influenza
viruses currently circulating are a good match with the influenza
vaccine. Vaccination remains the best method for preventing influenza
and its associated complications, and influenza vaccination is
recommended in all persons aged 6 months or older.
Interested readers should consult the original version via the source
URL to view the complete text and the accompanying figures. - Mod.CP]
See Also
Influenza (74): swine-origin H3N2 reassortant, vaccine candidate
20111203.3526
Influenza (73): WHO update 20111202.3519
Influenza (72): Europe, swine-origin H3N2 reassortant, risk assessment
20111130.3494
Influenza (71): USA (IA) swine-origin H3N2 reassortant, WHO
20111125.3448
Influenza (70): USA (IA) swine-origin H3N2 reassortant 20111124.3438
Influenza (69): USA (IA) swine-origin H3N2 reassortant 20111123.3430
Influenza (67): WHO update 20111118.3403]
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