lunes, 27 de abril de 2009

¿Cuánto Tiempo Debería Mantenerse la Suspensión de Actividades?

Cuando el jueves pasado por la noche se hizo público el problema de influenza porcina en el paíse, se determinó cancelar actividades escolares como una medida para evitar concentraciones humanas en donde se dieran las condiciones favorables de contagio. En los siguientes días esta disposición se extendió a otras actividades culturales, espectáculos, religiosos y ahora la suspensión de clase es en todo el país. Este tipo de medidas no médicas o clínicas para hacer frente a este problema no son nuevas, y han jugado un papel muy importante en otros eventos.
En un post en Sciencie in Society, Flu intervention: then and now, hace referencia a un estudio sobre la experiencia en la segunda década del siglo pasado en Estados Unidos con la "Influenza Española"
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The study examined the experience of 23 cities in implementing various public health measures, and measured the impact of response time and duration of intervention. They found that quick action (as measured by when flu cases rose to double the baseline number of cases) had a strong correlation with reduced mortality, and that maintaining the measures was important to keep the disease from spreading.
St. Louis, for example, closed schools and canceled public gatherings early, and maintained quarantines for over ten weeks, leading to a significantly lower mortality rate. However, not all cities were as proactive; the median duration of these interventions was only four weeks, insufficient to protect the population. Some cities were even counterproductive: Philadelphia hosted a military parade to promote war bonds, over the objections of numerous doctors and public health officials. Soon afterwards, it became one of the hardest-hit cities in the US.
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En suma, lo que dice es que aquellas ciudades que optaron por alargar sus cuarentenas vieron una menor tasa de mortalidad que aquellas que no lo hicieron.
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Aún no sabemos a ciencia cierta la gravedad del problema actual, pero definitivamente todo indica que la acción gubernamental de suspender concentraciones públicas va en el sentido corredcto (no se si fue o no a tiempo), y de continuar aumentando el procentaje de casos, podríamos ver un periodo de no actividad más prolongado, con el consecuente costo económico, pero en favor de proteger la vida humana.

2 comentarios:

Anónimo dijo...

Saludos. Interesante nota, del 2004.......
http://www.cidrap.umn.edu/cidrap/content/influenza/panflu/news/jan1404hybrids.html
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CDC to mix avian, human flu viruses in pandemic study
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Robert Roos * News Editor
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Jan 14, 2004 (CIDRAP News) – One of the worst fears of infectious disease experts is that the H5N1 avian influenza virus now circulating in parts of Asia will combine with a human-adapted flu virus to create a deadly new flu virus that could spread around the world.
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That could happen, scientists predict, if someone who is already infected with an ordinary flu virus contracts the avian virus at the same time. The avian virus has already caused at least 48 confirmed human illness cases in Asia, of which 35 have been fatal. The virus has shown little ability to spread from person to person, but the fear is that a hybrid could combine the killing power of the avian virus with the transmissibility of human flu viruses.
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Now, rather than waiting to see if nature spawns such a hybrid, US scientists are planning to try to breed one themselves—in the name of preparedness.
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The Centers for Disease Control and Prevention (CDC) will soon launch experiments designed to combine the H5N1 virus and human flu viruses and then see how the resulting hybrids affect animals. The goal is to assess the chances that such a "reassortant" virus will emerge and how dangerous it might be.
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CDC officials confirmed the plans for the research as described recently in media reports, particularly in a Canadian Press (CP) story.
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Two ways to make hybrids
The plans call for trying two methods to create hybrid viruses, CDC spokesman David Daigle told CIDRAP News via e-mail. One is to infect cells in a laboratory tissue culture with H5N1 and human flu viruses at the same time and then watch to see if they mix. For the human virus, investigators will use A (H3N2), the strain that has caused most human flu cases in recent years, according to the CP report.
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The other method is reverse genetics—assembling a new virus with sets of genes from the H5N1 and H3N2 viruses. Reverse genetics has already been used to create H5N1 candidate vaccines in several laboratories, according to Daigle. The National Institutes of Health (NIH) said recently it would soon launch a clinical trial of one of those vaccines.
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Of the two methods, the co-infection approach was described as slower and more laborious, though closer to what happens in nature.
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Any viable viruses that emerge from these processes will be seeded into animals that are considered good models for testing how flu viruses behave in humans, according to Daigle. The aim will be to observe whether the animals get sick and whether infected animals can infect others.
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The World Health Organization (WHO) has been "pleading" for laboratories to do this research, because it could provide some evidence to back up the agency's warnings about the risk of a flu pandemic, according to the CP report.

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Klaus Stohr, head of the WHO's global influenza program, was quoted as saying that if none of the hybrids caused disease, the agency might be inclined to dial down its level of concern. But if the experiments produce highly transmissible and pathogenic viruses, the agency will be more worried, he said.
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Safety precautions
Because of the obvious risks in creating viruses with the potential to spark a pandemic, the work will be done in a biosafety level 3 (BSL-3) laboratory at the CDC in Atlanta, Daigle told CIDRAP News.............................
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"We recognize that there is concern by some over this type of work. This concern may be heightened by reports of recent lab exposures in other lab facilities," he said. "But CDC has an incredible record in lab safety and is taking very strict precautions."
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Daigle said the US Department of Agriculture requires that highly pathogenic avian influenza (HPAI) viruses be treated as "Select Agents" and that research on them must be done in BSL-3 labs with "enhancements." These include "special provisions to protect both laboratory workers and the environment."
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BSL-3 is the second highest level of laboratory biosecurity. It is used for work with pathogens that may cause serious or potentially lethal disease if inhaled, such as tuberculosis or St. Louis encephalitis, according to the CDC.
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CDC experiments with HPAI viruses have to pass reviews by the agency's Institutional Biosafety Committee and Animal Care and Use Committee, Daigle said. The facilities involved are inspected by the USDA and the CDC's Office of Safety and Health, and staff members who work with Select Agents require special clearance.
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It's been done before
The upcoming experiments will not break entirely new ground for the CDC, the CP story revealed. The agency already has made hybrid viruses with H5N1 samples isolated from patients in Hong Kong in 1997, when the virus first caused human disease.
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The results of that research have not yet been published, and the CDC has said little about them. In the CP report, Dr. Nancy Cox, head of the CDC's influenza branch, commented only, "Some gene combinations could be produced and others could not."
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Daigle added little to that. He said, "The reassortment work with the 1997 isolate was intermittently interrupted with SARS [severe acute respiratory syndrome] and then the 2004 H5N1 outbreak. We are currently concentrating our efforts on understanding the pathogenicity of the 2004 strains (non-reassortants) in mammalian models."
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He said the CDC hopes to prepare a report on that research "in the near future."
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See also:
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CDC information on biosafety levels
http://www.cdc.gov/od/ohs/symp5/jyrtext.htm
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Francisco Valdivia dijo...

Estoy de acuerdo con la medida del Gobierno Federal de suspender clases y cancelar eventos de espectáculos, deportivos y religiosos donde se pueda dar una concentración humana que genere contagios.
Con lo que no estoy de acuerdo es con la medida del Gobierno del DF de cerrar restaurantes, me parece una medida radical, equivocada y contraproducente. Con el afán de usar el tema de la influenza como medio político y electorero, el jefe de gobierno, queriendo adelantarse al Gobierno Federal, tomó esta medida "de vanguardia" que solo afectará, al de por sí ya afectado por la ley anti-tabaco, sector restaurantero. Ahora las personas acuden a los puestos ambulantes, los puestos en la calle, que como todos sabemos son un foco de infecciones por no ser higiénicos, todos compartiendo la misma cuchara de la salsa, los limones, etc. Estos ambulantes no han sido molestados, ni clausurados, vaya, nadie les ha dicho nada. ¿Habrá una intención electoral detrás?