Re: INDONESIA - Human cases - August 22, 2007+
Re: INDONESIA - Human cases - August 22, 2007+
Study Confirms Limited Human-To-Human Spread of Avian-Flu Virus in Indonesia in 2006
New software will provide first real-time analysis of such
infectious-disease outbreaks
SEATTLE, Aug. 28 /PRNewswire/ -- In the first systematic, statistical
analysis of its kind, infectious-disease-modeling experts at Fred
Hutchinson Cancer Research Center confirm that the avian influenza A (H5N1)
virus in 2006 spread between a small number of people within a family in
Indonesia. The findings, by biostatistician Ira M. Longini Jr., Ph.D., and
colleagues, appear online and will be published in the Sept. 1 print
edition of Emerging Infectious Diseases, a journal of the Centers for
Disease Control and Prevention.
Co-authors on the paper were biostatisticians M. Elizabeth (Betz)
Halloran, M.D., D.Sc., and Yang Yang, Ph.D.; and epidemiologist Jonathan
Sugimoto, M.H.S., a pre-doctoral research associate. All are within the
Hutchinson Center's Public Health Sciences Division and Vaccine and
Infectious Disease Institute.
The researchers based their findings on a cluster of eight flu cases
within an extended family in northern Sumatra. Using a computerized
disease-transmission model that took into account the number of infected
cases, the number of people potentially exposed, the viral-incubation
period and other parameters, the researchers produced the first statistical
confirmation of humans contracting the disease from each other rather than
from infected birds.
The cluster contained a chain of infection that involved a 10-year-old
boy who probably caught the virus from his 37-year-old aunt, who had been
exposed to dead poultry and chicken feces, the presumed source of
infection. The boy then probably passed the virus to his father. The
possibility that the boy infected his father was supported by genetic
sequencing data. Other person-to-person transmissions in the cluster are
backed up with statistical data. All but one of the flu victims died, and
all had had sustained close contact with other ill family members prior to
getting sick -- a factor considered crucial for transmission of this
particular flu strain.
In an attempt to contain the spread of the virus, the local health
authorities eventually placed more than 50 surviving relatives and close
contacts under voluntary quarantine and all, except for pregnant women and
infants, received antiviral medication as a precaution.
"The containment strategy was implemented late in the game, so it could
have been just luck that the virus burned out," Longini said. "It went two
generations and then just stopped, but it could have gotten out of control.
The world really may have dodged a bullet with that one, and the next time
we might not be so lucky," he said.
Should a strain of avian flu acquire the ability to cause sustained
human-to-human transmission, the results could be catastrophic, Longini
said. "If not contained, the outbreak could spread worldwide through the
global transportation network faster than the appropriate vaccine supply
could be made available. That's why it's so important to ascertain whether
human-to-human transmission is happening as well as the virulence of the
strain." The researchers estimated the secondary-attack rate of the virus
in Indonesia -- the risk of one infected person passing it to another -- to
be 29 percent, a level of infectiousness similar to statistical estimates
for seasonal influenza A in the United States.
The researchers also aimed their statistical transmission-assessment
technology at another large avian-flu cluster in eastern Turkey that in
2006 infected eight people, four of whom died. In this case, the
researchers did not find statistical evidence of human-to-human
transmission, most likely due to a lack of sufficient data. "There probably
was person-to-person spread there as well but we couldn't get all the
information we needed for the analysis," Yang said.
The methods and software used in this research led to the development
of a software application called TranStat, which will allow first
responders to enter, store and perform real-time analysis of data from
infectious-disease outbreaks. This tool soon will be available online free
of charge via MIDAS, the Models of Infectious Disease Agent Study, which is
supported by the National Institute of General Medical Sciences.
"We know the key to preventing a pandemic is early detection,
containment and mitigation with antiviral therapy and this tool will enable
those on the front lines, such as physicians, epidemiologists and other
public-health officials, to carry that out efficiently," Halloran said.
"The manuals on how to collect the necessary data are decades old. They are
very outdated and incomplete. Often people on the front lines don't know
what to do; they don't collect the correct data to assess whether
transmission is occurring. TranStat will prompt people to gather precisely
the data that needs to be collected to better understand and contain any
infectious-disease spread, not just the avian flu," Sugimoto said.
If a smoldering disease cluster does flame out of control, the software
also could be used to estimate the important characteristics of the virus
-- such as its transmissibility, secondary-attack rate and reproductive
number -- which would give public-health officials a better chance at
slowing its spread until a vaccine or other effective control measures
could be implemented.
Yang and colleagues recently described the basis for the statistical
methods used in the research in The Annals of Applied Statistics.
The study was funded and supported by the National Institute of General
Medical Sciences MIDAS network and the National Institute of Allergy and
Infectious Diseases.
Longini and Halloran also are professors of biostatistics and Sugimoto
is a pre-doctoral student in the School of Public Health and Community
Medicine at the University of Washington.
At Fred Hutchinson Cancer Research Center, our interdisciplinary teams
of world-renowned scientists and humanitarians work together to prevent,
diagnose and treat cancer, HIV/AIDS and other diseases. Our researchers,
including three Nobel laureates, bring a relentless pursuit and passion for
health, knowledge and hope to their work and to the world. For more
information, please visit fhcrc.org.
CONTACT
Kristen Woodward
(206) 667-5095
kwoodwar@fhcrc.org
http://www.prnewswire.com/cgi-bin/s...07/0004652358&EDATE=TUE+Aug+28+2007,+07:00+AM
