[108104] in Cypherpunks
accidental bio attack; subway anonymity
daemon@ATHENA.MIT.EDU (Anonymous)
Thu Feb 4 17:48:59 1999
Date: Thu, 4 Feb 1999 23:20:09 +0100
From: Anonymous <nobody@replay.com>
To: cypherpunks@toad.com
Reply-To: Anonymous <nobody@replay.com>
>From: 7Pillars Partners <partners@sirius.infonex.com>
>Subject: [IWAR] BIO TB spread by train passenger
>
>TB spread by train passenger
>
> NEW YORK, Feb 03 (Reuters Health) -- A man with active tuberculosis (TB)
> who took a train journey from Chicago to Florida appears to have
> infected two other passengers, but researchers say that the likelihood
> of contracting TB on a train is ``probably minimal.''
>
> Researchers from the Centers for Disease Control and Prevention tracked
> down half of the 479 passengers and crew who were on one of the two
> passenger trains the infected man traveled on over a 2-day period in
> January 1996.
>
> Of the 240 passengers traced, the two who were infected had relatively
> close contact with the man: one had been seated near the ill passenger
> in the dining car, the other had engaged in a brief conversation with
> him.
>
> During his journey, the man became so ill that he requested medical
> assistance. Two weeks after being hospitalized, the man died of
> pulmonary hemorrhage.
>
> He had spent a total of 29.1 hours on two trains and 5.5 hours on a bus
> to which train passengers were transferred at one point during the
> journey.
>
> ``If sharing the train airspace had been a significant risk, we would
> have expected transmission to increase with extended duration of travel
> in the same section or car with the ill passenger,'' wrote the
> researchers. ``This finding was not observed. Although all potentially
> exposed persons were not evaluated, the duration of travel of those who
> underwent complete testing was similar to that of those who did not.''
>
> They suggest that the train's ventilation system, which circulated
> outside air 10 to 15 times per hour, probably reduced the overall number
> of infectious droplets in the air, which may have limited transmission
> of the disease.
>
> Similarly, the man's efforts to cough into the hood of his sweatshirt
> may have cut down on the spread of droplets before they were expelled
> into the air. ``Transmission may have occurred when the ill passenger
> was less likely or less able to cover his cough, such as during speaking
> or eating,'' wrote the researchers.
>
> They acknowledge, however, that they were unable to contact about half
> of the other passengers and therefore do not know how many, if any, of
> them contracted the disease.
>
> In an accompanying editorial, Dr. Mallory D. Witt of the
> Allergy/Immunology, and Infectious Diseases division of Harbor-UCLA
> Medical Center in Torrance, California raises concern about the
> possibility for transmission of tuberculosis on subway trains. Witt
> points out that unlike inter-city trains, subways do not have
> ventilation systems that draw in outside air except when the doors open
> in the station. Subways are crowded, often with passengers who live in
> large urban areas where TB rates are high. And subway travel is
> anonymous; there is no way to identify or track passengers who may be
> exposed to TB while traveling on a subway train.
>
> Nevertheless, Witt also believes that risks are minimal. ''In 1997, 20
> million persons rode passenger trains, 541 million rode local commuter
> and light-rail trains, and 2.2 billion rode subways. Thus, if a
> significant risk of disease transmission existed in this setting, on a
> per trip basis, the results would be obvious.''
>
> SOURCE: Clinical Infectious Diseases 1999;28:52-56, 57-58.
>
>
