Modeling targeted layered containment of an influenza pandemic in the United States

[sharon sanders]

ENVIRONMENTAL SCIENCES
Modeling targeted layered containment of an influenza pandemic in the United States
<nobr>M. Elizabeth Halloran^*^,^,</nobr>, <nobr>Neil M. Ferguson</nobr>, <nobr>Stephen Eubank^?</nobr>, <nobr>Ira M. Longini, Jr.^*^,</nobr>, <nobr>Derek A. T. Cummings</nobr>, <nobr>Bryan Lewis^?</nobr>, <nobr>Shufu Xu</nobr>, <nobr>Christophe Fraser</nobr>, <nobr>Anil Vullikanti^?</nobr>, <nobr>Timothy C. Germann^||</nobr>, <nobr>Diane Wagener^**</nobr>, <nobr>Richard Beckman^?</nobr>, <nobr>Kai Kadau^||</nobr>, <nobr>Chris Barrett^?</nobr>, <nobr>Catherine A. Macken^||</nobr>, <nobr>Donald S. Burke</nobr>, and <nobr>Philip Cooley^**</nobr>
^?Virginia Bioinformatics Institute, Virginia Polytechnical Institute and State University, Blacksburg, VA 24061; Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261; **Research Triangle Institute, Research Triangle Park, NC 27709; Department of Infectious Disease Epidemiology, Imperial College, London W21PG, England; ^||Los Alamos National Laboratories, Los Alamos, NM 87545; *Department of Biostatistics, School of Public Health and Community Medicine, University of Washington, Seattle, WA 98195; and Program in Biostatistics and Biomathematics, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109
Edited by Barry R. Bloom, Harvard School of Public Health, Boston, MA, and approved January 15, 2008 (received for review July 23, 2007)
Abstract
Planning a response to an outbreak of a pandemic strain of influenzais a high public health priority. Three research groups usingdifferent individual-based, stochastic simulation models haveexamined the consequences of intervention strategies chosenin consultation with U.S. public health workers. The first goalis to simulate the effectiveness of a set of potentially feasibleintervention strategies. Combinations called targeted layeredcontainment (TLC) of influenza antiviral treatment and prophylaxisand nonpharmaceutical interventions of quarantine, isolation,school closure, community social distancing, and workplace socialdistancing are considered. The second goal is to examine therobustness of the results to model assumptions. The comparisonsfocus on a pandemic outbreak in a population similar to thatof Chicago, with 8.6 million people. The simulations suggestthat at the expected transmissibility of a pandemic strain,timely implementation of a combination of targeted householdantiviral prophylaxis, and social distancing measures couldsubstantially lower the illness attack rate before a highlyefficacious vaccine could become available. Timely initiationof measures and school closure play important roles. Becauseof the current lack of data on which to base such models, furtherfield research is recommended to learn more about the sourcesof transmission and the effectiveness of social distancing measuresin reducing influenza transmission.

pdf - OPEN SOURCE

http://www.pnas.org/cgi/reprint/0706849105v1

[gsgs]

Re: Modeling targeted layered containment of an influenza pandemic in the United States

OK, 6 pages .pdf
looks important enough to me, I printed it and will read it.
Someone else ?


will try to write a summary.
My current estimate, influenced by earlier modeling papers
and by 1918-data is, that no more than about a 50&#37; reduction
can be achieved by these measures.


---------------------------------

hmm, seems that their models show upto 90% reductions.

But:
> We caution against overinterpretation...

also:

>...use of even poorly matched,low-efficacy vaccines would
>greatly enhance...

[gullwing]

Re: Modeling targeted layered containment of an influenza pandemic in the United States

I consider myself a learned man with an advanced degree in science but I have to say that I had a hard time following this mathematical and computerized model. Certainly the intellectual horsepower of all the scientists and the institutions makes it hard to dispute. Then after all is said and done it makes you wonder what the entire purpose of these computerized studies are for? Seems to me that it is an exercise with a preordained purpose. The purpose was to support the current government plan of social distancing. All of the study was done using a mathematic model and had little bases in reality. For instance it does matter how many days a person is asymptomatic walking around spreading the virus. I'm not sure that as an unknown variable it doesn't affect out come. I think it is not a simple matter to say that all exposed family members are given prophylaxis within 24 hours then multiply this by 60% compliance or 30% compliance. I for one do not think that the Public Health system has a method of delivery or a plan of delivery of antiviral medication that could attain a success rate of 30%. They could have by distributing antivirals prior to a pandemic or by allowing internet prescribing of anti-virals but they have rejected both ideas.
They also speak of the issue of using a fixed variable for percentage of cases diagnosed. I am not sure how that works? For instance if the first case of avian influenza arrived in the first hospital in the US no measures would be taken until patients stopped acting like seasonal flu. That would be patients admitted to an ICU with a viral pneumonia or deaths. Then the serum would be sent to the CDC for testing. What is the current turn around time on something like that? 4 days? Then at what point will that data go to the governor and how long until something is done? Usually in most countries there is an initial phase of "don't worry nothing definitive is known". So the first sentinel cases are going to spread a lot of disease to a lot of people. Later on it will be assumed that if you have shaking chills and a fever you have flu and if you have flu we will treat it like Pandemic flu (rather then the other way around). So I don't know how much reality there is in this computer model. They reference closing schools and theaters to decrease social interactions (and didn't mention shopping for food?). I am not sure what a percentage of time this accounts for. I didn't see any reality based numbers. You can't simply make the statement that if we closed all of the small buisnesses for 1-2 weeks as if you could. No mention of how compliance would taper off once people ran out of food and water.
Interesting to develope a computer model but I am not sure it has real time reality. Sort of like calculating how many people can be evacuated out of New Orleans versus how fast a hurricane is blowing and how hard the rain is falling. Yes, I already know that you can't move as many people as fast when the weather is bad but other independent factors like do the buses have gas in them or do the drivers show up. These intangibles tend to predominate in most disasters.

[Malcolm]

Re: Modeling targeted layered containment of an influenza pandemic in the United States

I consider myself a learned man with an advanced degree in science but I have to say that I had a hard time following this mathematical and computerized model. Certainly the intellectual horsepower of all the scientists and the institutions makes it hard to dispute. Then after all is said and done it makes you wonder what the entire purpose of these computerized studies are for? Seems to me that it is an exercise with a preordained purpose. The purpose was to support the current government plan of social distancing. All of the study was done using a mathematic model and had little bases in reality. For instance it does matter how many days a person is asymptomatic walking around spreading the virus. I'm not sure that as an unknown variable it doesn't affect out come. I think it is not a simple matter to say that all exposed family members are given prophylaxis within 24 hours then multiply this by 60% compliance or 30% compliance. I for one do not think that the Public Health system has a method of delivery or a plan of delivery of antiviral medication that could attain a success rate of 30%. They could have by distributing antivirals prior to a pandemic or by allowing internet prescribing of anti-virals but they have rejected both ideas.
They also speak of the issue of using a fixed variable for percentage of cases diagnosed. I am not sure how that works? For instance if the first case of avian influenza arrived in the first hospital in the US no measures would be taken until patients stopped acting like seasonal flu. That would be patients admitted to an ICU with a viral pneumonia or deaths. Then the serum would be sent to the CDC for testing. What is the current turn around time on something like that? 4 days? Then at what point will that data go to the governor and how long until something is done? Usually in most countries there is an initial phase of "don't worry nothing definitive is known". So the first sentinel cases are going to spread a lot of disease to a lot of people. Later on it will be assumed that if you have shaking chills and a fever you have flu and if you have flu we will treat it like Pandemic flu (rather then the other way around). So I don't know how much reality there is in this computer model. They reference closing schools and theaters to decrease social interactions (and didn't mention shopping for food?). I am not sure what a percentage of time this accounts for. I didn't see any reality based numbers. You can't simply make the statement that if we closed all of the small buisnesses for 1-2 weeks as if you could. No mention of how compliance would taper off once people ran out of food and water.
Interesting to develope a computer model but I am not sure it has real time reality. Sort of like calculating how many people can be evacuated out of New Orleans versus how fast a hurricane is blowing and how hard the rain is falling. Yes, I already know that you can't move as many people as fast when the weather is bad but other independent factors like do the buses have gas in them or do the drivers show up. These intangibles tend to predominate in most disasters.

I totally agree with gullwing.

Modeling has severe limitations as a result of the questionable assumptions made.

Putting numbers to intangibles is always a guess.

Numbers assigned to intangibles and unknowns can be manipulated to produce a preconceived outcome.

However, social distancing is an EXCELLENT way to try to limit the spread of epidemics.

How to achieve social distancing is the question?

[Malcolm]

Pandemic flu plan would put Chicago on lockdown

News article on Modeling study above in PNAS

http://www.sciam.com/article.cfm?id=pandemic-flu-plan-would-p

Pandemic flu plan would put Chicago on lockdown



Reuters - March 10, 2008
Pandemic flu plan would put Chicago on lockdown

By Julie Steenhuysen

CHICAGO (Reuters) - Containing an influenza pandemic in a large U.S. city like Chicago would require widespread school closings, quarantines of infected households and bans on public gatherings, U.S. researchers said on Monday.

But, if done quickly and well, such steps could reduce infections by as much as 80 percent, said researcher Stephen Eubank of Virginia Tech in Blacksburg, Virginia, based on a computer simulation of just such an event.

"If you implement it early and people comply, you can save a lot of people. You can make it look a lot more like a seasonal flu than the 1918 pandemic," said Eubank, referring to a global flu epidemic that started in 1918 and killed between 40 million and 100 million people.

Health experts almost universally agree that a global epidemic -- a pandemic -- of influenza is inevitable. Flu is always circulating but, every few decades, a completely new strain emerges and makes millions sicker than usual.

Government estimates suggest vaccines and drugs will not be enough to slow or prevent a flu pandemic, and the U.S. pandemic plan includes ways to limit the spread by closing schools and implementing strategies to reduce contact with infected people.

Eubank led one of three teams of scientists who ran computer simulations to see if drug and social containment efforts could slow the spread of an influenza pandemic in a major U.S. city such as Chicago, which has a population of about 8.6 million people.

All three teams found that a combination of antiviral drugs -- such as Roche AG and Gilead Sciences Inc.'s Tamiflu -- and social distancing efforts would be needed to slow the spread of a pandemic flu, they report in the Proceedings of the National Academy of Sciences.

"Depending on how fast it is spreading, it seems as though you really need to throw everything you can at it," Eubank said in a telephone interview.

NOT LIKE A SNOW DAY

The so-called social distancing measures they studied would dramatically alter the life of the city for a period of months -- long enough, Eubank said, for vaccine makers to develop a vaccine.

Schools and day-care centers would close. Theaters, bars, restaurants and ball parks would be shuttered.

Offices and factories would be open but hobbled as workers stay home to care for children. Infected people and their friends and families would be confined to their homes.

"We are not talking about simply shutting things down for a day or two like a snow day. It's a sustained period for weeks or months," he said.

"You wouldn't go out to the movies. You wouldn't congregate with people. You'd pretty much be staying home with the doors and windows battened down," he said.

While those measures seem draconian, Eubank said they are steps many people would take on their own in the face of a deadly flu outbreak.

"In the context of a very infectious disease that is killing a large number of the people, I think large fractions of the population won't have a problem with these recommendations," Eubank said.

He said that the models in the study are tools that suggest what could be done to slow a pandemic, but a lot of the pandemic plan's success would rely on the efforts of individuals to protect themselves and others from infection.

The study is available at http://www.pnas.org/cgi/doi/10.1073/pnas.0706849105.

(Editing by Maggie Fox and Jackie Frank)



This is a great unknown:

Will businesses and people comply with social distancing recommendations?

I don't think they will be able to.... since the majority do not know the severity of pandemic threat, have not prepared, and have no savings.

[AlaskaDenise]

Re: Modeling targeted layered containment of an influenza pandemic in the United States

I don't think they will be able to.... since the majority do not know the severity of pandemic threat, have not prepared, and have no savings.

Business as usual won't be an option. I expect food/essentials distribution plans will be the only way to maintain any needed lockdown.

.