MMWR Dispatch reports on infections with a swine-origin influenza A (H1N1)
virus in the U.S. and other countries as of April 28
On April 28, CDC published "Update: Infections
with a Swine-Origin
Influenza A (H1N1) Virus--United States and Other Countries, April
28, 2009" as an electronic MMWR Dispatch. The MMWR Dispatch is
reprinted below in its entirety, excluding references and a figure.
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Since April 21, 2009, CDC has reported cases of respiratory
infection with a swine-origin influenza A (H1N1) virus (S-OIV)
transmitted through human-to-human contact. This report updates
cases identified in U.S. states and highlights certain control
measures taken by CDC. As of April 28, the total number of
confirmed cases of S-OIV infection in the United States had
increased to 64, with cases in California (10 cases), Kansas (two),
New York (45), Ohio (one), and Texas (six). CDC and state and local
health departments are investigating all reported U.S. cases to
ascertain the clinical features and epidemiologic characteristics.
On April 27, CDC distributed an updated case definition for
infection with S-OIV (Box). [Note: Information in the box appears
between the rows of equal signs.]
BOX. CDC INTERIM GUIDANCE ON CASE DEFINITIONS FOR INVESTIGATIONS OF
HUMAN SWINE-ORIGIN INFLUENZA A (H1N1) CASES
The following case definitions are for the purposes of
investigations of suspected, probable, and confirmed cases of
swine-origin influenza A (H1N1) infection.
Case definitions for infection with swine-origin influenza a (H1N1)
A confirmed case of swine-origin influenza A (H1N1) virus infection
is defined as an acute febrile respiratory illness in a person and
laboratory-confirmed swine-origin influenza A (H1N1) virus
infection at CDC by either of the following tests:
(1) real-time reverse transcription-polymerase chain
reaction (rRT-PCR), or
(2) viral culture.
A probable case of swine-origin influenza A (H1N1) virus infection
is defined as acute febrile respiratory illness in a person who is
- positive for influenza A, but negative for H1 and H3 by influenza
A suspected case of swine-origin influenza A (H1N1) virus infection
is defined as acute febrile respiratory illness in a person
- with onset within 7 days of close contact with a person who has a
confirmed case of swine-origin influenza A (H1N1) virus
- with onset within 7 days of travel to a community, either within
the United States or internationally, which has one or more
confirmed swine-origin influenza A (H1N1) cases, or
- who resides in a community in which one or more confirmed swine-origin influenza cases have occurred.
Of the 47 patients reported to CDC with known ages, the median age
was 16 years (range: 3-81 years), and 38 (81%) were aged <18 years;
51% of cases were in males. Of the 25 cases with known dates of
illness onset, onset ranged from March 28 to April 25. To date, no
deaths have been reported among U.S. cases, but five patients are
known to have been hospitalized. Of 14 patients with known travel
histories, three had traveled to Mexico; 40 of 47 patients (85%)
have not been linked to travel or to another confirmed case.
Information is being compiled regarding vaccination status of
infected patients, but is not yet available. According to the World
Health Organization (WHO), as of April 27, a total of 26 confirmed
cases of S-OIV infection had been reported by Mexican authorities.
Canada has reported six cases and Spain has reported one case.
EMERGENCY USE AUTHORIZATIONS
If an emerging public health threat is identified for which no
licensed or approved product exists, the Project BioShield Act of
2004 authorizes the Food and Drug Administration (FDA) commissioner
to issue an Emergency Use Authorization (EUA) so that promising
countermeasures can be disseminated quickly for the protection and
safety of the U.S. population.
In response to the current public health emergency involving swine-origin influenza, FDA issued four EUAs on April 27 to allow
emergency use of
- oseltamivir (Tamiflu) and zanamivir (Relenza) for the treatment
and prophylaxis of influenza (two EUAs),
- disposable N95 respirators for use by the general public, and
- the rRT-PCR Swine Flu Panel for diagnosis.
Oseltamivir is FDA-approved for treatment and prevention of
influenza in adults and children aged >=1 year. Zanamivir is FDA-approved for treatment of influenza in adults and children aged >=7
years who have been symptomatic for <2 days, and for prevention of
influenza in adults and children aged >=5 years. The EUA allows the
use of oseltamivir for treatment of influenza in children aged <1
year and prevention of influenza in children aged 3 months-1 year.
Additionally, traditional prescribing and dispensing requirements
might not be met. Under the scope and conditions of current EUAs,
mass dispensing of both antiviral medications will be allowed per
state and/or local public health authority.
FDA has authorized use of certain N95 respirators to help reduce
wearer exposure to pathogenic biological airborne particulates
during a public health emergency involving S-OIV. On April 27, CDC
published guidelines for the use of N95 respirators. For example,
respirators should be considered for use by persons for whom close
contact with an infectious person is unavoidable. This can include
selected individuals who must care for a sick person (e.g., family
member with a respiratory infection) at home. Additional
information is available at http://www.cdc.gov/swineflu/masks.htm
Currently, no FDA-cleared tests specifically for the S-OIV strain
exist in the United States or elsewhere. For this purpose and to
meet the significant increase in demand for influenza testing
throughout the country, CDC has developed the rRT-PCR Swine Flu
Panel to expand and maintain the operational capabilities of public
health or other qualified laboratories by providing a detection
tool for the presumptive presence of S-OIV.
CONTROL MEASURES AT PORTS OF ENTRY AND TRAVEL WARNING FOR MEXICO
CDC, in collaboration with industry and federal partners, is
continuing to conduct routine illness detection at ports of entry
with heightened awareness for travelers who might be infected with
S-OIV. During April 19-27, 15 cases of illness in travelers
entering the United States from Mexico that were clinically
consistent with S-IV infection were detected. Of these 15 cases,
two were laboratory confirmed as swine-origin influenza A (H1N1).
Nine travelers remain in isolation pending completion of
evaluation, and four travelers were released to complete travel
after influenza virus infection was ruled out.
WHO has declared a Public Health Emergency of International
Concern. As part of its responsibilities under the International
Health Regulations, CDC is prepared to implement additional
screening measures for international flights, if deemed necessary,
to prevent exportation of S-OIV. In addition, CDC in collaboration
with the U.S. Department of Homeland Security, is distributing
travelers health alert notices to all persons traveling to
countries with confirmed cases of S-OIV infection.
CDC has recommended that U.S. travelers avoid nonessential travel
to Mexico (http://wwwn.cdc.gov/travel/contentswineflumexico.aspx).
However, CDC might revise its travel guidance as the outbreak in
Mexico evolves and is characterized more completely. Travelers who
cannot delay travel to Mexico should visit
http://www.cdc.gov/travel and follow the posted recommendations to
reduce their risk for infection.
NONPHARMACEUTICAL COMMUNITY MITIGATION
CDC has issued interim guidance for nonpharmaceutical community
mitigation efforts in response to human infections with S-OIV
recommendations for isolation of patients with cases of S-OIV,
household contacts, school dismissal, and other social distancing
interventions also are available at
http://www.cdc.gov/swineflu/mitigation.htm and will be updated as
the situation evolves.
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