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Clearing The Skies Could Stop An Epidemic

by Staff Writers

Los Angeles (SPX) Sep 13, 2006

A detailed analysis of influenza patterns indicates that the sharp dip

in air travel after September 11, 2001 slowed flu spread and delayed

the onset of the 2001-2002 U.S. flu season, report researchers at

Children's Hospital Boston. Their findings, published in the September

12, 2006 issue of the online journal PLoS Medicine, suggest that

limiting airline volume could buy critical time during a flu pandemic.

Most previous investigations of the effect of air travel on influenza

spread have relied on simulations of flu activity rather than actual data.

" The post-September 11th flight ban was a natural experiment on the

effect of flight restrictions on disease spread, " says

Brownstein, PhD, the paper's lead author and a faculty member of the

Children's Hospital Informatics Program (CHIP) at the Harvard-MIT

Health Sciences and Technology program. " For the first time we've been

able to show, using real data, that air travel spreads the flu,

suggesting that reducing the number of air passengers might ameliorate

a flu pandemic. "

The spread of avian flu (H5N1) in Asia and Europe, including some

likely cases of person-to-person transmission, has intensified debate

over whether flight restrictions should be imposed to curb emerging

flu pandemics. Both the World Health Organization (WHO) and the United

States government are considering such restrictions.

Using data on influenza mortality from the Centers for Disease Control

and Prevention (CDC), Brownstein and senior investigator,

Mandl, MD, MPH, a CHIP faculty member and an attending physician in

Children's Department of Emergency Medicine, measured the rate of

influenza spread across the U.S. during nine flu seasons, from 1996-97

to 2004-05.

During the first five flu seasons, flu mortality consistently peaked

on or around February 17. But in the flu season after September 11,

2001, the peak was delayed until March 2, nearly two weeks later than

average. In subsequent years, the peaks moved back toward February 17

as airline activity resumed its pre-9/11 levels.

In addition, analysis of laboratory surveillance data from the WHO and

CDC showed that in the 2001-2002 flu season, it took 53 days for flu

to spread across the U.S., 60 percent longer than the average time of

33 days.

By contrast, in France, where flight restrictions were not imposed,

there was no delay in flu activity during the 2001-2002 flu season.

Brownstein and Mandl, both also of Harvard Medical School, then

compared their data on flu spread with monthly estimates of passengers

on domestic and international flights, obtained from the U.S.

Department of Transportation.

For domestic flights, airline volume in November 2001 was an

especially strong predictor of flu spread. With the Thanksgiving

holiday, November is typically one of the busiest travel months of the

year, but in 2001, many people kept close to home or sought other

forms of travel. " Thanksgiving is when new flu strains often spread

across the country, " Brownstein notes.

For international flights, volume during September most strongly

predicted the U.S. flu peak, suggesting that September is a key month

for introduction of foreign flu strains. In September 2001,

international flights fell 27 percent (from 4.9 to 3.5 million

passengers), and peak flu mortality that winter was delayed by two

weeks. In 2002, international travel was still down by 10 percent, and

the U.S. peak was again delayed.

" When we first looked at our data we noticed that the 2001-2002 flu

season was highly aberrant, " Mandl recounts. " At first we thought it

was a problem with the data, but then we realized we were seeing the

shadow of September 11th cast upon the influenza season. "

http://www.terradaily.com/reports/Clearing_The_Skies_Could_Stop_An_Epidemic_999.\

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From our files:

Want to stop disease from spreading? Open a window

Mon Feb 26, 8:25 PM ET

WASHINGTON (Reuters) - Preventing the spread of disease in a hospital may be as

simple as opening a window, an international team of researchers reported on

Monday.

The low-tech solution could help prevent the spread of airborne infections such

as tuberculosis -- and ironically, old-fashioned hospitals with high ceilings

and big windows may offer the best design for this, they reported.

They worked better than modern " negative pressure " rooms, with expensive design

aimed at pumping out infected air, the researchers report in the Public Library

of Science journal PLoS Medicine.

" Opening windows and doors maximizes natural ventilation so that the risk of

airborne contagion is much lower than with costly, maintenance-requiring

mechanical ventilation systems, " wrote Rod Escombe of Imperial College London

and colleagues in their report.

" Old-fashioned clinical areas with high ceilings and large windows provide

greatest protection. Natural ventilation costs little and is maintenance free, "

they added.

For their report, Escombe and colleagues tested the air in eight hospitals in

Lima, Peru.

Wards built more than 50 years ago, with large windows and high ceilings, had

better ventilation than modern rooms that relied on natural ventilation.

And they were also superior to the mechanically ventilated rooms, they reported

in their study, available online at

http://medicine.plosjournals.org/perlserv/?request=get-document &

doi=10.1371/journal.pmed.0040068.

Tuberculosis is spread by bacteria that can float in the air and the researchers

calculated what their findings might mean for the spread of TB.

They estimated that in mechanically ventilated rooms, 39 percent of susceptible

people would become infected after 24 hours of exposure to an untreated TB

patient. This compared to a 33 percent infection rate in modern rooms with

windows open and 11 percent in a pre-1950-style room.

" We found that opening windows and doors provided median ventilation of 28 air

changes/hour, more than double that of mechanically ventilated negative-pressure

rooms ventilated at the 12 air changes an hour recommended for high-risk areas, "

they wrote.

Experts are looking at these factors in trying to prepare for a pandemic of

influenza.

" The current practice of sealing in the local environment is probably the wrong

route for hospital wards, " of University College London Hospitals

added in a commentary on the study.

http://news./s/nm/20070227/hl_nm/hospital_windows_dc_2