ProMED-mail |

Published Date: 2009-05-01 17:00:04
Subject: PRO/AH/EDR> Influenza A (H1N1) - worldwide (03)
Archive Number: 20090501.1646

INFLUENZA A (H1N1) - WORLDWIDE (03)
***********************************
A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>

In this update:
[1] More on origin
[2] NYC school outbreak
[3] Outbreak history
[4] WHO - update 7

******
[1] More on origin
Date: Wed 29 Apr 2009
Source: Science Insider, American Association for the Advancement of
Science (AAAS) [abbreviated and edited]
<http://blogs.sciencemag.org/scienceinsider/2009/04/exclusive-cdc-h.html>

Interview with Ruben Donis
--------------------------
Virologist Ruben Donis, chief of the molecular virology and vaccines
branch at the US Centers for Disease Control and Prevention [CDC],
spoke with Science Insider at length last night [28 Apr 2009] about
the swine flu virus causing the current outbreak. CDC's early
analyses raise several provocative possibilities. The stage appears
to have been set for this human outbreak by an outbreak over the past
decade of flu viruses in swine that combine strains from several
species. The 1st infected human may not even have been in North
America, let alone Mexico. Patient samples from Mexico taken over the
past several months reveal that this swine flu clearly exploded in
late March [2009], suggesting that it was not rapidly spreading in
that country, undetected, for very long.

Donis discussed the genetics of the virus -- the clues in this
mystery -- in detail. These include several of its 8 genes, which
code for surface proteins hemagglutinin (H) and neuraminidase (N),
the matrix that surrounds the nucleus, the nucleoprotein itself, and
3 polymerase enzymes called PA, PB1, and PB2.

We know it's quite similar to viruses that were circulating in the
United States and are still circulating in the United States and that
are self-limiting, and they usually only are found in Midwestern
states where there is swine farming. There's only one well-documented
case where the infection spread from one human to another. What we
know is that it is not common that there is sustained transmission in
people. Hemagglutinin, neuraminidase, and matrix, the 3 genes that
have the most public health interest, were sequenced, and then the
whole genome was completed. There similarities of about 94 percent in
the hemagglutinin [H] to the nearest strain we know. It's almost
equidistant to swine viruses from the United States and Eurasia. And
it's a lonely branch there. It doesn't have any close relatives.

The neuraminidase gene has close relatives in Asia. It's also swine.
The matrix gene same as neuraminidase.

For the avian and human sequences we have to step back 10 years to
1998, actually. Chris Olsen is one of the first that saw it, and we
saw the same in a virus from Nebraska and Richard Webby and Robert
Webster in Memphis saw it, too. There were unprecedented outbreaks of
influenza in the swine population. It was an H3 virus. The disease
was not very severe in healthy pigs. Everyone was very curious about
these H3 viruses. Since 1918, normally it's only H1N1 in swine. Then
all of a sudden there's H3N2 in swine in the Midwestern US. When
people analyzed what was inside those viruses, they realized there
were 3 different things. The PB1 gene, that was human. H3 and N2 also
were human. The PA and PB2, the 2 polymerase genes, were of avian
flu. The rest were typical North American swine viruses. Those
strains were the so-called triple reassortants.

The reality is good molecular surveillance in the pigs started in the
1970s. So if there were strains that were not very dominant between
the 1930s and the '70s, we wouldn't have detected them. This triple
reassortant was very successful and took over and dominated the
picture-to the point where the classical H1N1 was almost extinct. H3
was a different subtype, so there was no immunity in the pigs. It was
probably that they had new polymerase genes, too. The neuraminidase
and the matrix are the newest to be seen in North America. They were
not part of the team -- I talk about flu virus as teams of genes.
There are 8 players. They have these 2 new players from Asia.

One little detail we haven't discussed is [that] these Midwestern
viruses were exported to Asia. Korea and many countries import from
the US. Swine flu is economically not such a big deal that many
countries don't check for it. There are some parts of the puzzle I
don't have the answer to [such as the European lineage
contributions]. The genetic lineages of Asia and Europe mix quite a
bit.

[The question of the appearance of this virus in Mexico is
unresolved], but the mixing probably did not occur in Mexico. The
amazing thing is the hemagglutinins we are seeing in this strain are
a lonely branch that has been evolving somewhere and we didn't know
about it.

We have [a] 6 percent or higher percentage difference in
neuraminidases. You have multiple amino acids that differ. And single
amino acid changes can change receptor specificity. When you have so
many changes, you don't know which ones are responsible.

One traditional approach is to take advantage of viral modules that
allow you to assemble different teams, to make reassortants that take
a virus say from North America that doesn't transmit, and you swap
one gene from the virus that does transmit. If the hypothesis is that
hemagglutinin is responsible, you put in the background of the genes
from the old virus. You need an animal model, usually the ferret.

[The current outbreak strains] from Mexico and North America are
very, very similar. Many genes are identical. In the 8 or 9 viruses
we've sequenced, there is nothing different. We've received 300
samples from Mexico, and these cover the span of February, March, and
April [2009]. And you look at flu A, traditionally it's A/H1 or A/H3
or it's B up until the end of March. There are 2 or 3 cases up to
[the] last days of March that are swine. Then in April they
skyrocket. So all the cases in the DF [Mexico City] areas, where most
samples came from, it really transmits very efficiently. Flu is a
seasonal disease that peaks in winter. Maybe this will end in the
United States with the end of the flu season.

--
Communicated by:
ProMED-mail
<promed@promedmail.org>

[It seems irrefutable now that the current human outbreak strain of A
(H1N1) virus was preceded by outbreaks over the past decade of
influenza viruses in swine that combine strains from several species.
The 1st infected human may not even have been in North America, or
even Mexico. The site (or sites) of interaction of the different
strains contributing to the evolution of this unique influenza virus,
and the nature of the selective forces involved, remain unresolved.

The complete version of this interview in its question and answer
format can be viewed at the source URL above. - Mod.CP]

******
[2] NYC school outbreak
Date: Thu 30 Apr 2009
Source: CDC. MMWR Morb Mortal Wkly Rep 2009; 58 (dispatch): 1-3 [edited]
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0430a1.htm?s_cid=mm58d0430a1_e>

Swine-origin influenza A (H1N1) virus infection in a school - New
York City, April 2009
----------------------------------------------------------------------
On 24 Apr 2009, CDC reported 8 confirmed cases of swine-origin
influenza A (H1N1) virus (S-OIV) infection in Texas and California
(1). The strain identified in US patients was confirmed by CDC as
genetically similar to viruses subsequently isolated from patients in
Mexico (1). Since 24 Apr 2009, the number of cases in the United
States and elsewhere has continued to rise. As of 28 Apr 2009,
approximately half (45) of all US cases of S-OIV infection had been
confirmed among students and staff members at a New York City (NYC)
high school. This report describes the initial outbreak investigation
by the NYC Department of Health and Mental Hygiene (DOHMH) and
provides preliminary details about 44 of the 45 patients (the
remaining patient resides outside of NYC and was not included in the
analysis). The preliminary findings from this investigation indicate
that symptoms in these patients appear to be similar to those of
seasonal influenza. DOHMH will continue monitoring for changes in the
epidemiology and/or clinical severity of S-OIV infection.
Epidemiologic and Laboratory Investigations

Epidemiologic and laboratory investigations
-------------------------------------------
On 23 Apr 2009, DOHMH was notified of approximately 100 cases of mild
(uncomplicated) respiratory illness among students at an NYC school
(high school A) with 2686 students and 228 staff members. During
23-24 Apr 2009, a total of 222 students visited the school nursing
office and left school because of illness. Given initial reports on
24 Apr 2009 of what was later determined to be a large S-OIV outbreak
in Mexico, DOHMH decided to rapidly mobilize staff members to go to
high school A to collect nasopharyngeal swabs from any symptomatic
students. On 24 Apr 2009 (a Friday), DOHMH staff members collected
nasopharyngeal swabs from 5 newly symptomatic students identified by
the school nurse and 4 newly symptomatic students identified at a
nearby physician's office. A decision was made over the weekend 25-26
Apr 2009 not to open the school on Monday 27 Apr 2009. Because of
suspicion that the respiratory disease cases might be caused by
S-OIV, beginning 24 Apr 2009, DOHMH attempted to contact the
remaining 213 students reported by the nursing office to have left
school because of respiratory illness. Some of the most recently
symptomatic at the time of telephone contact were advised to visit a
specified emergency department for nasopharyngeal swab collection.
DOHMH also provided 24 Apr 2009 by DOHMH were identified by CDC as
S-OIV. During 26-28 Apr 2009, 37 (88 percent) of 42 specimens
collected in the emergency department and local physicians' offices
tested positive at CDC for S-OIV, bringing the total number of
confirmed cases to 44.

DOHMH conducted telephone interviews with the 44 patients with
confirmed S-OIV on 27 Apr 2009. Median age of the patients was 15
years (range: 14-21 years). All were students, with the exception of
one student teacher aged 21 years. 31 (70 percent) of the 44 were
female. 30 (68 percent) were non-Hispanic white; 7 (16 percent) were
Hispanic; 2 (5 percent) were non-Hispanic black; and 5 (11 percent)
were of other races. 4 patients reported travel outside NYC within
the United States in the week before symptom onset, and an additional
patient traveled to Aruba in the 7 days before symptom onset. None of
the 44 patients reported recent travel to California, Texas, or
Mexico.

Illness onset dates ranged from 20 Apr to 24 Apr 2009; 10 (23
percent) of the patients had illness onset on 22 Apr 2009, and 28 (64
percent) had illness onset on 23 Apr 2009. The most frequently
reported symptoms were cough (in 43 patients [98 percent]),
subjective fever (42 [9 percent]), fatigue (39 [8 percent]), headache
(36 [82 percent]), sore throat (36 [82 percent]), runny nose (36 [82
percent]), chills (35 [80 percent]), and muscle aches (35 [80
percent]). Nausea (24 [55 percent]), stomach ache (22 [50 percent]),
diarrhea (21 [48 percent]), shortness of breath (21 [48 percent]),
and joint pain (20 [46 percent]) were less frequently reported but
still common. Among 35 patients who reported a maximum temperature,
the mean was 102.2 deg F (39.0 deg C) (range: 99.0-104.0 deg F
[37.2-40.0 deg C]). In total, 42 (95 percent) patients reported
subjective fever plus cough and/or sore throat, meeting the CDC
definition for influenza-like illness (ILI) (2). At the time of
interview on 27 Apr 2009, 37 patients (84 percent) reported that
their symptoms were stable or improving, 3 (7 percent) reported
worsening symptoms (2 of whom later reported improvement), and 4 (9
percent) reported complete resolution of symptoms. Only one reported
having been hospitalized for syncope and released after overnight
observation.

Enhanced surveillance
---------------------
On 26 Apr 2009, DOHMH launched enhanced surveillance for
self-reported ILI among all students, staff members, and family
members of persons at high school A via an online survey. Students
and staff members were recruited via e-mail messages with a link to
the survey, followed by daily reminder e-mails. Active surveillance
at the school was impractical because a decision was made by DOHMH
and the school principal not to reopen the school for the start of
the new school week, 27 Apr 2009. Complete data from this ongoing
survey are not yet available, but preliminary results indicate
widespread influenza-like symptoms, with hundreds of students and
many staff members reporting symptoms that met the case definition
for ILI. Several students participating in the on-line survey (none
of whom had confirmed S-OIV) reported travel to Mexico during the
week before 20 Apr 2009; an undetermined number were symptomatic at
the time of survey participation.

DOHMH also initiated active surveillance for severe, hospitalized
febrile respiratory ILI among NYC residents, and this surveillance is
currently ongoing. On 26 Apr 2009, DOHMH staff members began
contacting all 61 NYC hospitals with medical and/or pediatric
intensive care units by telephone on a daily basis to identify
possible severe cases of S-OIV, defined by the presence of fever
100.4 deg F or higher (38 deg C or higher) and at least one of the
following: acute respiratory distress syndrome, pneumonia, or
respiratory distress. DOHMH physicians review all possible cases;
nasopharyngeal swabs are recommended for cases with no identified
etiology. Specimens are tested for influenza A at the NYC Public
Health Laboratory, and isolates that cannot be subtyped are sent to
CDC for further characterization. Active surveillance identified one
to 2 cases of severe hospitalized ILI per day for which further
testing was recommended. Results of the testing are not yet available.

Enhanced passive surveillance also is ongoing. Doctors are asked via
daily reminders on the Health Alert Network to report any
hospitalized patients with fever and unexplained pneumonia or
respiratory distress to DOHMH. All case reports are reviewed by DOHMH
physicians, who contact providers reporting cases of severe illness
consistent with possible swine influenza and arrange nasopharyngeal
testing if warranted. In addition, DOHMH conducts syndromic
surveillance for the following: emergency department visits for fever
or influenza-like illness; drug sales for oseltamivir and other
prescription drugs for influenza; and school absenteeism.

[Reported by: HT Jordan, MD, MC Mosquera, MD; Swine Flu Investigation
Team, New York City Dept of Health and Mental Hygiene, New York. H
Nair, PhD, AM France PhD, EIS officers, CDC]

MMWR editorial note
-------------------
To date [30 Apr 2009], this school-based outbreak is the largest
cluster of S-OIV cases reported in the United States (2). The
findings from this investigation (in a population known to be at low
risk for severe disease from seasonal influenza) indicate that
symptoms appear to be similar to those of seasonal influenza (3). The
risk for severe disease among higher risk groups is not yet known.
Additional assessment of the extent of illness in NYC is ongoing.

In crafting a local response to S-OIV, DOHMH has relied upon several
years of pandemic preparedness planning, adapted to the specific
characteristics of the current outbreak in NYC. Given the spectrum of
disease observed thus far in NYC, DOHMH has given highest priority to
active surveillance for severe illness in order to assure DOHMH's
ability to rapidly detect any change in the virulence or epidemiology
of the virus that would prompt consideration of changes in current
policy regarding use of antivirals and community control measures.
This decision also was influenced by the need to prioritize use of
the public health laboratory's resources on testing those cases with
clinical or epidemiologic characteristics that, if confirmed to be
S-OIV, might influence a change in the DOHMH's recommendations for
public health control measures. DOHMH's current primary goals are to
assess the severity of disease in infected persons and to maintain
the ability to detect changes in the epidemiology and clinical
presentation of the virus. Aggressive containment in NYC is not a
feasible strategy because the virus originated outside NYC and has
been reported in multiple other locales.

At this time, NYC health-care providers have been advised by DOHMH to
report all patients with severe, unexplained febrile respiratory
illness, and to report patients with mild (uncomplicated) cases of
ILI only if they are associated with a cluster of illness (that is, 3
or more cases of ILI) in an institution. NYC providers have been
advised to test patients with severe, unexplained febrile respiratory
illnesses for influenza A but not to test patients with mild
(uncomplicated) ILI unless they have conditions that increase their
risk for more severe illness (3). DOHMH is recommending treatment
with oseltamivir or zanamivir for 1) hospitalized persons with
suspected, probable, or confirmed illness, or with severe febrile
unexplained respiratory illness pending testing for swine influenza,
or 2) patients with mild (uncomplicated) ILI and underlying
conditions (such as, chronic cardiovascular or renal disorders or
immunosuppression) that increase the risk for more severe illness
because of influenza. DOHMH is recommending treatment for any patient
with mild (uncomplicated) ILI permissively only if started within 48
hours of symptom onset. Antiviral prophylaxis is being recommended
for 1) health-care workers who provided care to patients with
suspected, probable, or confirmed swine influenza without using
appropriate personal protection or 2) asymptomatic household or other
close contacts of ill persons of suspected, probable, or confirmed
swine influenza who are at higher risk for complications of influenza
or are health-care workers themselves. Persons with mild
(uncomplicated) ILI are being advised to stay home for 7 days after
symptom onset or 24-48 hours after symptom resolution, whichever is
longer, and to cover their coughs and sneezes and wash their hands
frequently. But neither testing nor presumptive antiviral therapy are
currently recommended for these persons.
Guidance for health-care providers is available via the DOHMH Health
Alert Network at <http://www.nyc.gov/health/nycmed>.
Additional information from DOHMH on swine influenza is available at
<http://www.nyc.gov/health> and
<http://www.nyc.gov/html/doh/downloads/pdf/cd/swine_flu_faq.pdf>.

Interim guidance from CDC on treatment and chemoprophylaxis for swine
influenza is available at
<http://www.cdc.gov/flu/swine/recommendations.htm>.
Interim guidance on infection control for swine influenza is
available at
<http://www.cdc.gov/swineflu/guidelines_infection_control.htm>.
Additional information about swine influenza is available at
<http://www.cdc.gov/flu/swine/index.htm>.

References
----------
1. CDC: Swine influenza A (H1N1) infections-California and Texas,
April 2009. MMWR 2009; 58: 437-9 [available at
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5816a7.htm>].
2. CDC: Update: infections with a swine-origin influenza A (H1N1)
virus-United States and other countries, 28 Apr 2009. MMWR 2009; 58:
433-4 [available at
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5816a5.htm>].
3. CDC: Prevention and control of influenza: recommendations of the
Advisory Committee on Immunization Practices (ACIP), 2008. MMWR 2008;
57(No. RR-7) [available at
<http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5707a1.htm>].

--
Communicated by:
ProMED-mail
<promed@promedmail.org>

[Overall the symptoms of infection with the swine-origin influenza
virus appear to be similar to those of seasonal influenza. - Mod.CP]

******
[3] Outbreak history
Date: Thu 30 Apr 2009
Source: CDC. MMWR Morb Mortal Wkly Rep 2009; 58 (dispatch): 1-3 [edited]
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0430a2.htm?s_cid=mm58d0430a2_e>

Outbreak of swine-origin influenza A (H1N1) virus infection - Mexico,
March-April 2009
----------------------------------------------------------------------
In March and early April 2009, Mexico experienced outbreaks of
respiratory illness and increased reports of patients with
influenza-like illness (ILI) in several areas of the country. On 12
Apr 2009, the General Directorate of Epidemiology (DGE) reported an
outbreak of ILI in a small community in the state of Veracruz to the
Pan American Health Organization (PAHO) in accordance with
International Health Regulations. On 17 Apr 2009, a case of atypical
pneumonia in Oaxaca State prompted enhanced surveillance throughout
Mexico. On 23 Apr 2009, several cases of severe respiratory illness
laboratory confirmed as swine-origin influenza A (H1N1) virus (S-OIV)
infection were communicated to the PAHO. Sequence analysis revealed
that the patients were infected with the same S-OIV strain detected
in 2 children residing in California (1). This report describes the
initial and ongoing investigation of the S-OIV outbreak in Mexico.

Enhanced surveillance
---------------------
On 17 Apr 2009, in response to the increase in reports of respiratory
illness, DGE issued a national epidemiologic alert to all
influenza-monitoring units and hospitals (Table 1 [available at
source URL]). The alert asked hospitals to report all patients with
severe respiratory illness and recommended collection of diagnostic
respiratory specimens from these patients within 72 hours of illness
onset. On 18 Apr 2009, DGE staff visited 21 hospitals throughout the
country to confirm the apparent increase in illness incidence.

After laboratory confirmation of S-OIV infection on 23 Apr 2009, DGE
developed case definitions. A suspected case was defined as severe
respiratory illness with fever, cough, and difficulty breathing. A
probable case was defined as a suspected case in a patient from whom
a specimen had been collected and tested positive for influenza A. A
confirmed case was defined as a probable case that tested positive
for S-OIV by real-time reverse--transcription polymerase chain
reaction (RT-PCR). Health-care officials were contacted and asked to
provide retrospective and ongoing data for persons having illness
consistent with these case definitions and seeking care on or after 1
Mar 2009.

During 1 Mar-30 Apr 2009, a total of 1918 suspected cases were
reported, including 286 probable and 97 confirmed cases [data
supplemented by a figure in the original text]. A total of 84 deaths
were reported. A majority of case-reports were for hospitalized
patients, reflecting the concentration of surveillance efforts within
hospitals. However, DGE also received reports from sites conducting
routine seasonal influenza surveillance of patients with ILI. Of 1069
patients with suspected and probable cases for whom information was
available, 755 were hospitalized, and the remaining 314 were examined
in outpatient settings or emergency departments. Suspected or
probable cases were reported from all 31 states and from the Federal
District of Mexico. The 4 areas with the most cases were Federal
District (213 cases), Guanajuato (141), Aguascalientes (93), and
Durango (77). In other states, the number of suspected or probable
cases ranged from two to 46. Suspected and probable cases were
identified in all age groups. Mexico routinely monitors seasonal
influenza in a network of outpatient facilities throughout the
country. Fifty-one influenza A positive specimens from 6 states were
collected during 4 Jan-11 Mar 2009 in this surveillance network. All
of these specimens tested negative for S-OIV at CDC.

Confirmed cases of S-OIV infection
----------------------------------
As of 30 Apr 2009, DGE surveillance activities, focusing on patients
with severe respiratory disease, had identified 97 patients with
laboratory-confirmed S-OIV infection, including 7 persons who had
died. The 1st of the 97 patients reported onset of illness (any
symptom) on 17 Mar 2009, and the most recent patients reported onset
on 26 Apr 2009. Laboratory confirmation of S-OIV infection for the
most recent 73 of these 97 cases was reported on the evening of 29
Apr 2009. Collection of additional information on these 73 cases is
ongoing. Of the 24 patients for whom demographic and clinical
information is available, 20 (83 percent) were hospitalized, 3 were
examined in outpatient settings, and one had illness that was not
medically attended. Patients ranged in age from less than 1 to 59
years, with 79 percent aged 5 to 59 years; 15 (62 percent) patients
were female. Patients with confirmed S-OIV infection were identified
in 4 states: Federal District (15 cases), Mexico State (7), Veracruz
(one), Oaxaca (one). Of the 7 deaths, 6 occurred in Federal District,
and one occurred in Oaxaca.

Among the 16 patients with complete clinical records, 15 reported
fever, 13 reported cough, 10 reported tachypnea, and 9 reported
dyspnea. In addition, 7 of 16 patients reported either vomiting or
diarrhea. Of these 7 patients, 2 reported vomiting only, 2 reported
diarrhea only, and 3 reported both. 8 of 16 patients were admitted to
intensive-care units; of these, 7 required mechanical ventilation,
and 6 subsequently died after developing acute respiratory distress
syndrome. 12 of 15 patients with radiography records available had
confirmed pneumonia. 3 of the 16 patients had underlying health
conditions. Information on the duration of hospitalization before
death was available for 6 patients and ranged from 1 to 18 days
(median: 9 days).

Prevention and control measures
-------------------------------
On 24 Apr 2009, the Council for General Hygiene convened with the
President of the Mexican Republic and decreed the closure of all
schools in the Federal District and metropolitan area of Mexico City.
Incoming and outgoing airport passengers were informed of the
outbreak and advised to seek care immediately should they experience
symptoms of ILI. Other measures included 1) disseminating educational
messages regarding respiratory hygiene through mass media; 2)
distributing masks and alcohol hand-sanitizer to the public; and 3)
discouraging large public gatherings, including church services,
theater events, and soccer games. On 25 Apr 2009, a national decree
allowed for house-isolation of any person with a suspected case, and
on 27 Apr 2009, school closures were mandated throughout the country.

[Reported by: General Directorate of Epidemiology, Ministry of
Health, Mexico; Pan American Health Organization; World Health
Organization; Public Health Agency of Canada; CDC (United States)]

MMWR editorial note
-------------------
Understanding the epidemiology and clinical profiles of recent cases
of S-OIV infection in Mexico can help inform regional, national, and
global control measures in response to the emergence of S-OIV
infection. Important areas for investigation worldwide include
evidence of person-to-person transmission, the geographic
distribution of disease, the clinical spectrum of disease, and the
effectiveness of mitigation strategies.

Previous instances of human-to-human transmission of other swine
viruses have been reported to result in small clusters of disease and
limited generations of disease transmission (2,3). Several findings
indicate that transmission in Mexico involves person-to-person spread
with multiple generations of transmission. Patients with probable and
laboratory-confirmed disease have presented over a period of 4 weeks.
Limited contact tracing of patients with laboratory-confirmed disease
also has identified secondary cases of ILI.

The clinical spectrum of S-OIV illness is not yet well characterized
in Mexico. However, evidence suggests that S-OIV transmission is
widespread and that less severe (uncomplicated) illness is common.
Patients with confirmed disease have been identified in several
states, and suspected cases have been identified in all states, which
suggests that S-OIV transmission is widespread. In addition, several
countries are reporting S-OIV infection among persons who have travel
histories involving different parts of Mexico in the 7 days before
illness onset. To date [30 Apr 2009], case-finding in Mexico has
focused on patients seeking care in hospitals, and the selection of
cases for laboratory testing has focused on patients with more severe
disease. Therefore, a large number of undetected cases of illness
might exist in persons seeking care in primary-care settings or not
seeking care at all. Additional investigations are needed urgently to
evaluate the full clinical spectrum of disease in Mexico, the
proportion of patients who have severe illness, and the extent of
disease transmission.

To expedite confirmation of disease in additional patients, the World
Health Organization (WHO) Influenza Collaborating Center in Atlanta,
Georgia, has placed the genetic sequence of S-OIV from California in
GenBank. Specific primers for S-OIV have been developed and will be
distributed through the WHO Global Influenza Surveillance Network to
reference laboratories throughout the world. As of 26 Apr 2009, the
National Laboratory for Public Health in Mexico has capacity to
perform PCR for S-OIV.

The epidemiologic characteristics of this outbreak underscore the
importance of monitoring the effectiveness of community mitigation
efforts, non pharmaceutical interventions, and clinical management
practices in anticipation of a possible pandemic.

References
----------
1. CDC: Swine influenza A (H1N1) infection in two children-Southern
California, March-April 2009. MMWR 2009; 58: 400--2 [available at
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5815a5.htm>].
2. Wells DL, Hopfensperger DJ, Arden NH, et al: Swine influenza virus
infections. Transmission from ill pigs to humans at a Wisconsin
agricultural fair and subsequent probable person-to-person
transmission. JAMA 1991; 265: 478-81 [abstract available at
<http://www.ncbi.nlm.nih.gov/pubmed/1845913>].
3. Myers KP, Olsen CW, Gray GC: Cases of swine influenza in humans: a
review of the literature. Clin Infect Dis 2007; 44: 1084-8 [abstract
available at <http://www.ncbi.nlm.nih.gov/pubmed/17366454>].

--
Communicated by:
ProMED-mail
<promed@promedmail.org>

[It would seem that the clinical spectrum of S-OIV illness is still
not yet well characterized in Mexico. However, the evidence suggests
that S-OIV transmission is widespread and that less severe
(uncomplicated) illness is common. - Mod.CP]

******
[4] WHO - update 7
Date: Fri 1 May 2009
Source: WHO Epidemic and Pandemic Alert and Response (EPR) Disease
Outbreak News [edited]
<http://www.who.int/csr/don/2009_05_01/en/index.html>

Influenza A (H1N1) - WHO update 7
---------------------------------
The situation continues to evolve rapidly. As of 06:00 GMT, 1 May
2009, 11 countries have officially reported 331 cases of influenza A
(H1N1) infection.

The United States Government has reported 109 laboratory confirmed
human cases, including one death. Mexico has reported 156 confirmed
human cases of infection, including 9 deaths.

The following countries have reported laboratory confirmed cases with
no deaths: Austria (1), Canada (34), Germany (3), Israel (2),
Netherlands (1), New Zealand (3), Spain (13), Switzerland (1), and
the United Kingdom (8).

Further information on the situation will be available on the WHO
website on a regular basis. WHO advises no restriction of regular
travel or closure of borders. It is considered prudent for people who
are ill to delay international travel and for people developing
symptoms following international travel to seek medical attention, in
line with guidance from national authorities.

There is also no risk of infection from this virus from consumption
of well-cooked pork and pork products. Individuals are advised to
wash hands thoroughly with soap and water on a regular basis and
should seek medical attention if they develop any symptoms of
influenza-like illness.

Daily updates will be posted on the Influenza A (H1N1) website at
<http://www.who.int/csr/disease/swineflu/en/index.html>

--
Communicated by:
ProMED-mail Rapporteur Marianne Hopp

See Also