[escepticos] Cross-listing sobre gripe porcina

[Pedro J. Hdez]

Interesante mensaje de Christine Hansen que me ha dado permiso para el
cross-listing + un boletín fresquito de ProMED

---

I happen to know something about this topic, because I am finishing a
doctoral dissertation that deals with emerging infectious disease.  In
fact, I visited the CDC's pandemic flu response facility in January.

First, the H1N1 virus that infects these pigs is not the same virus
that has been in the news for the past few years, the H5N1 'bird flu.'
 However, many strains of influenza can infect both birds and pigs,
and pigs are sometimes considered genetic 'mixing vessels' which
produce new strains that are transmitted to humans.

>From what I have read, H1N1 is endemic in pig populations in the U.S.
This is also quite different from H5N1, because massive attempts are
underway to keep the strain from becoming endemic in domestic bird
populations worldwide (I'm sure you've all heard of the chicken
cullings in Asia).

A key factor in the swine flu deaths which does seem to make them
dangerous is that the virus can be transmitted human-to-human.  In the
case of H5N1, so far the virus has always passed from birds into
humans, and has not mutated to a human-to-human strain.  Influenza is
certainly one of the most easily transmissible viruses in the world,
so once it can spread human-to-human, it's almost impossible to put
the genie back in the bottle and contain the virus' spread.

In the sense that it seems capable of passing human-to-human, then,
the H1N1 might be dangerous.

However, from the few reports I have seen in the news, it seems that
the victims have been primarily children.  This is the pattern for a
very typical strain of flu, in that most strains strike the elderly or
children.  In the case of both the 1918 flu and the H5N1 strain,
though, this is not the case.  Those at highest risk seemed to be
people in the healthiest years, such as young adults.  This seems to
be because certain strains produce a dangerous immune response which
is proportional to the overall health of the immune system of the
infected person, so that ironically, those with the healthiest immune
systems are at greatest risk of death.

Although this is a bit of a surmise, it does seem that the most
dangerous pandemic strains are those which involve this unusual immune
response.  I see no evidence that the H1N1 is doing this, although
there is pretty sketchy information.

As many on this list have written, some strain of flu will almost
certainly strike and cause a pandemic, because we are overdue for one,
historically speaking.  However, no one knows what strain it might be.
 H7 strains may be strains to watch, in addition to H5.

As you probably know, the natural reservoir of influenza virus is wild
aquatic birds, which carry the strains harmlessly.  However, some
strains of influenza virus can infect a wide variety of species, and
in some of these species, they produce very serious illness.  The
effects of H5N1 or some H7 strains in domestic chickens would be good
examples, but influenza viruses can also sometimes infect felines,
dogs, rats, mice, and can even be carried by certain types of insects.

Since the viruses circulate in various species, sometimes visibly and
sometimes not, and since influenza mutates very rapidly, it is
extremely difficult to predict what strain might emerge at what time,
in what way.  However, historically speaking, bird flu viruses have
been the most dangerous.  The 1918 flu is considered to have been
caused by a bird flu.

Having personally visited a number of the infectious disease response
teams in this country, I can tell you that they are quite worried
about the possibility of H5N1 mutating to a human-to-human strain.
Based on what I have seen and my conversations with a number of
people, I think this concern is by far the most pressing one in the
area of emerging infectious disease. Experts are watching for signs of
human-to-human mutated strains on a daily basis.

While the swine flu may also prove dangerous, I don't think it is
causing the same type of concerns as H5N1.

On the other hand, anyone who tries to predict the fine nuances of any
flu is treading on thin ice, because all influenza viruses are
notoriously nimble in their genetic changes and are inherently
unpredictable.

INFLUENZA A (H1N1) VIRUS, SWINE, HUMAN - NORTH AMERICA (02)
***********************************************************
A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>
Update:
[1] and [2] Strain identity
[3] Pandemic warning
[4] Outbreak in NY ?
******
[1] Strain identity
Date: Fri 24 Apr 2009
Source: CIDRAP News [edited]
<http://www.cidrap.umn.edu/cidrap/content/influenza/panflu/news/apr2409swine.html>

Labs confirm same swine flu in deadly Mexican outbreaks
-------------------------------------------------------
Samples from a deadly respiratory illness outbreak in Mexico match swine
influenza isolates from patients in the United States who had milder
illnesses, an official from the US Centers for Disease Control and
Prevention (CDC) said today [24 Apr 2009], fueling speculation that the
World Health Organization (WHO) could be on the verge of raising the global
pandemic alert level. Richard Besser, MD, CDC's acting director, told
reporters today during a press teleconference that the development is
worrisome. "Our concern has grown since yesterday, based on what we've
learned," he said. "We do not know if this will lead to the next pandemic,
but our scientists are monitoring it and take the threat very seriously."
The swine flu A/H1N1 strain has been confirmed in one more US citizen, a
child from San Diego who has recovered, raising the total number of US
cases to 8, Besser said. The virus contains gene segments from 4 different
influenza types: North American swine, North American avian, human, and
Eurasian swine.
WHO said today that Mexican officials have reported 3 separate events. In
the Federal District, the number of cases rose steadily through April, and
as of yesterday, more than 854 cases of pneumonia, 59 of them fatal, had
been reported in Mexico City. The illness outbreak in Mexico City prompted
the country's health minister, Jose Cordova, to cancel classes in Mexico
City today and advise students and adults to avoid crowded public places
and large events, Bloomberg News reported. Mexican officials also reported
24 cases with 3 deaths from an influenza-like illness in San Luis Potosi,
in the central part of the country, and 4 cases with no deaths in Mexicali,
near the US border, WHO reported.
The virus in Mexico has primarily struck otherwise healthy young adults,
WHO said, which is a departure from seasonal influenza, which typically
affects the very young and very old. CDC's laboratory analyzed 14 samples
from severely ill Mexican patients and found that 7 of them had the same
swine flu mix as the virus that infected the US patients. Besser called the
analysis preliminary, however, and said that CDC doesn't yet have enough
information to draw conclusions. "We still don't have enough information
about the extent of the spread or the illness spectrum." WHO said today
that Canada's national laboratory has confirmed swine flu A/H1N1 in 18
isolates from Mexican patients, 12 of which were genetically identical to
the swine flu viruses from California.
WHO and CDC both said they were sending representatives to Mexico to assist
local authorities, and WHO said it has alerted its Global Alert and
Response Network. Besser said that WHO will likely convene an expert panel
to discuss raising the pandemic alert level from 3 (human infection with
new influenza subtype with only rare human-to-human spread) to 4 (small
clusters with localized human-to-human transmission). He said the experts
will consider 3 factors: the novelty of the virus, disease severity, and
how easily transmission of the virus is sustained. Global health officials
might consider a containment strategy such as dispatching antiviral
medications to affected parts of Mexico in an attempt to stop the spread of
the virus, but Besser said that such a measure might not work, because
there are signs that the virus has already spread from human to human over
long distances. "A focused, well defined area is not something we've seen
here," he said. CDC officials have said the swine flu A/H1N1 virus is
susceptible to the newer antivirals oseltamivir (Tamiflu) and zanamivir
(Relenza), but not the older ones, amantadine and rimantadine. Jeff
McLaughlin, a spokesman for GlaxoSmithKline, the maker of Relenza, told
CIDRAP News that the company is watching the swine flu developments
closely. Terry Hurley, a spokesman for Roche, which produces Tamiflu, said
its "rapid response stockpile" is on 24-hour standby, as usual, for
deployment to WHO, which has not yet requested it.
The threat from the swine flu virus serves as a reminder for individuals
and businesses to think about their own level of preparedness, Besser said.
"This is a time for people to be thinking about that teachable moment." So
far, federal officials have not changed their travel recommendations to
California, Texas, or Mexico, though they have issued an advisory about the
increased health risk in certain parts of Mexico, urging travelers to take
standard precautions such hand washing, staying home when sick, and using
good coughing and sneezing hygiene.
[byline: Lisa Schnirring]
--
communicated by:
ProMED-mail
<promed en promedmail.org>
[The "swine" influenza A(H1N1) virus associated with current outbreaks of
respiratory illness in the southern region of the USA and in Mexico appears
to be a complex reassortant containing genome components from avian, human,
and swine virus sources. Such a virus is unique and it is too early to
conclude that this virus has originated in swine.
According to the CDC website (<http://www.cdc.gov/swineflu/>) swine
influenza (swine flu) is a respiratory disease of pigs caused by type A
influenza viruses that regularly cause outbreaks of influenza among pigs.
Swine flu viruses do not normally infect humans; however, human infections
with swine flu do occur, and cases of human-to-human spread of swine flu
viruses has been documented. From December 2005 through February 2009, a
total of 12 human infections with swine influenza were reported from 10
states in the United States. Since March 2009, a number of confirmed human
cases of the new strain of swine influenza A (H1N1) virus infection in
California, Texas, and Mexico have been identified.
Whatever the origin of the current outbreak virus it is likely that the
designation swine influenza virus will stick. - Mod.CP]
******
[2] Strain identity
Date: Fri 24 Apr 2009
Source: CBC News [abbreviated and edited]
<http://www.cbc.ca/health/story/2009/04/24/health-flu-mexico090424.html>

Canadian lab confirms human swine flu cases in Mexico
-----------------------------------------------------
"Today we have received results which confirm that the virus is human swine
influenza," Leona Aglukkaq told a press conference in Ottawa, Ontario,
Canada. A handful of cases of flu-like illness in Canadian residents who
recently returned from Mexico are being monitored; however, "there have
been no confirmed cases of human swine influenza yet" here, said Dr David
Butler-Jones, Canada's chief public health officer.
Mexico sent 51 specimens for testing to Canada's National Microbiology
Laboratory on Wednesday [21 Apr 2009]. 16 positives of swine flu were found
among the samples. Mexican health minister Jose Angel Cordova said on
Friday that 20 people were killed in the outbreak and 1004 were infected
throughout the country, prompting WHO to convene an emergency meeting on
Saturday. Officials closed schools, museums and libraries in Mexico City on
Friday to limit spread of the virus.
Dr Rich Besser, acting head of the US Centers for Disease Control (CDC),
said early analysis of Mexican samples of the virus showed it is very
similar to those responsible for 8 American cases, one confirmed on Friday.
All the US victims have recovered. Canada is working with Mexican and US
health officials to confirm that the virus in both countries is linked and
is in fact a new strain of influenza A H1N1 human swine virus, he added.
"This is an interesting virus. It's a brand new virus, not only to humans
but to the world," said Dr Frank Plummer, scientific director of the
Winnipeg lab. "About 80 per cent of the virus is highly related to a North
American body [?] of swine flu that's been around for a number of years,
but about 20 per cent of it comes from an Eurasian variety of swine flu 1st
seen in Thailand, so it's recombined [re-assorted ?] to create something
totally new. How it did that, where it did it, when it did it, I don't
think we know yet."
CDC said the current strain of swine flu includes genetic material from 4
sources: North American swine influenza viruses, North American avian
influenza viruses, human influenza virus, and swine influenza viruses found
in Asia and Europe -- a new combination that has not been recognized
anywhere in the world before. There appears to be human-to-human spread in
both the US and Mexico over a wide geographic area at this point, but
investigators are still checking for direct contact with swine.
WHO spokesperson Gregory Hartl said the agency needs to determine whether
the outbreaks constitute an international public health threat. Hartl also
said 12 of 18 samples taken from victims in Mexico showed the virus had a
genetic structure identical to that of the virus found in California
earlier this week. But he said the agency needs more information before it
changes its pandemic alert level, which currently stands at 3 on a scale of
one to 6. The virus was 1st reported earlier this week as US health
officials scrambled to deal with the diagnoses of 7 people with the
never-before-seen strain in Texas and California. The states share a border
with Mexico not far from a town where 2 deaths were reported.
Hartl said health officials are dealing with 3 separate events in Mexico,
with most of the cases in and around the capital, Mexico City. Most of the
cases have occurred in healthy young adults, he added. "Because these cases
are not happening in the very old or the very young, which is normal with
seasonal influenza, this is an unusual event and a cause for heightened
concern," Hartl said in an interview from WHO headquarters in Geneva. It is
also rare to see such high flu activity so late in the season, he said.
"The end of April, especially in a place like Mexico, you would think that
we would see quite a steep decline," said Hartl.
On Thursday [23 Apr 2009], Canadian health officials issued advice warning
travellers who have recently returned from Mexico to be on alert for
flu-like symptoms that could be connected to the illness.
--
communicated by:
Steven McAuley
Medical student
University of Otago
Dunedin, New Zealand
<sbmcauley en gmail.com>
******
[3] Pandemic warning
Date: Sat 25 Apr 2009
Source: MSNBC [edited]
<http://www.msnbc.msn.com/id/30398682>

Health officials prepare for swine flu "pandemic"
-------------------------------------------------
A new swine flu strain that has killed as many as 68 people and sickened
more than 1000 across Mexico has "pandemic potential," the WHO chief said
on Saturday [25 Apr 2009], and it may be too late to contain the sudden
outbreak. CDC has stepped up surveillance across the United States. "We are
worried," said CDC's Dr Anne Schuchat. "We don't think we can contain the
spread of this virus," said Schuchat, interim deputy director for the
Science and Public Health Program. "We are likely to find it in many other
places." Because cases have been detected in California, Texas, and in
several sites in Mexico, officials now must work to detect infections and
reduce their severity, if possible. "It's time to prepare, time to think
ahead and to be prepared for some uncertainty," she told reporters in a
telephone briefing on Saturday.
Two dozen new suspected cases were reported Saturday [25 Apr 2009] in
Mexico City alone. Schools were closed and all public events suspended in
the capital until further notice -- including more than 500 concerts and
other gatherings in the metropolis of 20 million. A hot line fielded 2366
calls in its 1st hours from frightened city residents who suspected they
might have the disease. Soldiers and health workers handed out masks at
subway stops, and hospitals dealt with crowds of people seeking help.
WHO's director-general, Margaret Chan, said the outbreak of the
never-before-seen virus is a very serious situation and has "pandemic
potential". But she said it is still too early to tell if it would become a
pandemic. "The situation is evolving quickly," Chan said in a telephone
news conference in Geneva. "A new disease is by definition poorly
understood. "This virus is a mix of human, pig, and bird strains that
prompted the WHO to meet Saturday to consider declaring an international
public health emergency -- a step that could lead to travel advisories,
trade restrictions and border closures. Spokesman Gregory Hartl said a
decision would not be made on Saturday.
Scientists have warned for years about the potential for a pandemic from
viruses that mix genetic material from humans and animals. Another reason
to worry is that authorities said the dead so far don't include vulnerable
infants and elderly. The Spanish flu pandemic, which killed at least 40
million people worldwide in 1918-19, also 1st struck otherwise healthy
young adults. This swine flu and regular flu can have similar symptoms --
mostly fever, cough, and sore throat, though some of the US victims who
recovered also experienced vomiting and diarrhea. But unlike with regular
flu, humans don't have natural immunity to a virus that includes animal
genes -- and new vaccines can take months to bring into use.
But experts at WHO and CDC say the nature of this outbreak may make
containment impossible. Already, more than 1000 people have been infected
in as many as 14 of Mexico's 32 states, according to daily newspaper El
Universal. Tests show 20 people have died of the swine flu, and 48 other
deaths were probably due to the same strain.
CDC and Canadian health officials were studying samples sent from Mexico,
and airports around the world were screening passengers from Mexico for
symptoms of the new flu strain, saying they may quarantine passengers. But
CDC officials dismissed the idea of trying that in the United States. They
noted there had been no direct contact between the cases in the San Diego
and San Antonio areas, suggesting the virus had already spread from one
geographic area through other undiagnosed people. "Anything that would be
about containing it right now would purely be a political move," said
Michael Osterholm, a University of Minnesota pandemic expert.
Mexican President Felipe Calderon said his government only discovered the
nature of the virus late on Thursday, with the help of international
laboratories. "We are doing everything necessary," he said in a brief
statement. But the government had said for days that its growing flu
caseload was nothing unusual, so the sudden turnaround angered many who
wonder if Mexico missed an opportunity to contain the outbreak.
Across Mexico's capital, residents reacted with fatalism and confusion,
anger, and mounting fear at the idea that their city may be ground zero for
a global epidemic. Authorities urged people to stay home if they feel sick
and to avoid shaking hands or kissing people on the cheeks.
--
communicated by:
Charles H Calisher, PhD
Professor, Arthropod-borne and Infectious Diseases Laboratory
Department of Microbiology, Immunology and Pathology
3195 Rampart Rd, Delivery Code 1690, Foothills Campus
Fort Collins, CO 80523-1690
College of Veterinary Medicine and Biomedical Sciences
Colorado State University
<calisher en cybersafe.net>
******
[4] Suspected outbreak in New York
Date: Fri 24 Apr 2009
Source: WCBS TV News [edited]
<http://wcbstv.com/health/swine.flu.nyc.2.994071.html>

Possible swine flu outbreak at NYC prep school
----------------------------------------------
New York City health officials say that about 75 students at a Queens high
school have fallen ill with flu-like symptoms and testing is under way to
rule out the strain of swine flu that has killed dozens in Mexico. The
Health Department's Dr Don Weiss said on Friday [24 Apr 2009] that a team
of agency doctors and investigators were dispatched to the private St
Francis Preparatory School the previous day after students reported fever,
sore throat, cough, aches, and pains. No one has been hospitalized.
The handful of sick students who remained at the school were tested for a
variety of flu strains. If they're found to have a known human strain that
would rule out swine flu. Results could take several days. In the meantime,
the school says it's postponing an evening event and sanitizing the
building over the weekend.
Mexican authorities said 60 people may have died from a swine flu virus in
Mexico, and world health officials worry it could unleash a global flu
epidemic. Mexico City closed schools, museums, libraries, and state-run
theaters across the metropolis on Friday in hopes of containing the
outbreak that has sickened more than 900. The US Centers for Disease
Control and Prevention (CDC) said tests show some of the Mexico victims
died from the same new strain of swine flu that sickened 8 people in Texas
and California. It's a frightening new strain that combines genetic
material from pigs, birds and humans.
WHO was looking closely at the 60 deaths -- most of them in or near
Mexico's capital. It wasn't yet clear what flu they died from, but
spokesman Thomas Abraham said "We are very, very concerned. We have what
appears to be a novel virus and it has spread from human to human," he
said. "It's all hands on deck at the moment."
WHO raised its internal alert system on Friday, preparing to divert more
money and personnel to dealing with the outbreak. President Felipe Calderon
cancelled a trip and met with his Cabinet to coordinate Mexico's response.
The government has 500 000 flu vaccines and planned to administer them to
health workers, the highest risk group. There are no vaccines available for
the general public in Mexico, and authorities urged people to avoid
hospitals unless they had a medical emergency, since hospitals are centers
of infection. Some Mexican residents have started wearing blue surgical
masks for extra protection, reports CBS News correspondent Adrienne Bard.
The federal health minister has warned people not to go near anyone with a
respiratory infection and to avoid kissing -- a traditional Mexican greeting.
--
communicated by:
ProMED-mail rapporteur Mary Marshall
[If infection by the novel swine flu virus is confirmed, it will represent
a dramatic extension of the range of the outbreak virus from the southern
states and Mexico to the north east of the United States. There is no
reason to conclude at present, however, that this is anything other than an
outbreak of seasonal influenza virus infection (or for that matter another
common respiratory virus). - Mod.CP]
[see also:
Influenza A (H1N1) virus, swine, human - N America 20090425.1552
Acute respiratory disease - Mexico, swine virus susp 20090424.1546
Influenza A (H1N1) virus, swine, human - USA (02): (CA, TX) 20090424.1541
Influenza A (H1N1) virus, swine, human - USA: (CA) 20090422.1516
Influenza A (H1N1) virus, swine, human - Spain 20090220.0715
2008
---
Influenza A (H1N1) virus, swine, human - USA (TX) 20081125.3715
2007
---
Influenza A (H2N3) virus, swine - USA 20071219.4079
2006
---
Influenza, swine, human - USA (IA): November 2006 20070108.0077]
....................cp/ejp/sh

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-- 
Pedro J. Hdez
Ecos del futuro
http://ecos.blogalia.com