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HICNet Medical News Digest Mon, 06 Mar 1995 Volume 08 : 
Issue 06

Today's Topics:

 [MMWR] Trends in Sexual Risk Behavior Among High School Students
 [MMWR] Update: Influenza Activity
 [MMWR] Availability of Draft Recommendations for HIV Counseling...
 [MMWR] Erratum: Vol 44 #5
 [MMWR - March 3, '95] Exposure of Passengers and Flight Crew to ...

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

To: hicnews
Students

 Trends in Sexual Risk Behavior Among High School Students --
 United States, 1990, 1991, and 1993

 Since the early 1980s, adolescents in the United States have
experienced high rates of unintended pregnancies (1) and sexually
transmitted diseases (STDs) (2), including HIV infection (3). Since 
1990,
CDC's Youth Risk Behavior Surveillance System has enabled measurement of
priority health-risk behaviors among high school students at the 
national,
state, and local levels (4). This report examines data from the 1990, 
1991,
and 1993 national Youth Risk Behavior Survey (YRBS)* to describe trends 
in
selected self-reported sexual risk behaviors among U.S. high school
students.
 The YRBS employed a cross-sectional, three-stage, cluster sample of
students in grades 9-12 in public and private schools in all 50 states 
and
the District of Columbia. For 1990, 1991, and 1993, sample sizes were
11,631, 12,272, and 16,296, respectively, and the overall response rates
were 64%, 68%, and 70%, respectively. To enable separate analysis of 
black
and Hispanic students, schools with high proportions of these students 
were
oversampled; numbers of students in other racial groups were too small 
for
meaningful analysis. A weighting factor was applied to each student 
record
to adjust for nonresponse and oversampling. Trends were assessed only 
for
sexual risk behaviors measured by questions identically worded in each
survey year. To determine temporal differences, 95% confidence intervals
were calculated for each estimate by using SUDAAN (5).
 From 1990 to 1993, the percentages of high school students remained
constant for those who reported ever having had sexual intercourse 
(i.e.,
sexually experienced), ever having had sexual intercourse with four or 
more
partners, having had sexual intercourse during the 3 months preceding 
the
survey (i.e., sexually active), having used alcohol or drugs before last
sexual intercourse, and having used birth control pills at last sexual
intercourse (Table 1). In contrast, the percentage of those who reported
condom use at last sexual intercourse increased significantly, from 
46.2%
in 1991 to 52.8% in 1993 (Table 1); however, subgroup analyses indicated
a significant increase in condom use only among females (from 38.0% to
46.0%) and blacks (from 48.0% to 56.5%) (Table 2).

Reported by: Div of Adolescent and School Health, National Center for
Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note: During the 1980s, the proportion of adolescents who
reported being sexually experienced increased substantially in the 
United
States (6). The findings in this report indicate that, from 1990 through
1993, the proportion of high school students who reported being sexually
experienced remained stable, while an increasing percentage of sexually
active students used condoms, thereby reducing their risk for unintended
pregnancy and STDs, including HIV infection.
 The sex, grade, and race/ethnicity findings in this report may 
assist
in identifying groups with higher prevalences of sexual risk behaviors.
However, the underlying causes (e.g., education levels, economic 
factors,
or cultural influences) for within-subgroup differences could not be
addressed in this study.
 In 1991 and 1992, two health outcomes associated with sexual risk
behaviors--live births and gonorrhea--also declined. Live-birth rates 
among
15-19-year-olds decreased in 40 states and the District of Columbia,
increased in eight states, and were stable in two states. In addition,
rates of gonorrhea decreased among 15-19-year-old males in 45 states and
the District of Columbia and among 15-19-year-old females in 41 states 
and
the District of Columbia. Of the 41 areas reporting declines in live-
birth
rates, 34 also reported declines in gonorrhea rates for both males and
females; six other states reported declines for either males or females.
Overall, live-birth rates for adolescents decreased significantly (2%) 
(7),
and gonorrhea rates decreased significantly among both adolescent males 
and
adolescent females (20% and 13%, respectively) (8).
 The plateau in the proportion of high school students who reported
being sexually experienced, the increasing rates of condom use among 
high
school students, and the decreasing rates of live births and gonorrhea
among adolescents may reflect, in part, efforts to reduce risks for HIV
infection and other STDs among adolescents. For example, since 1986, CDC
has collaborated with local, state, and national health and education
agencies, national and community-based organizations, and the media to
increase development, implementation, and awareness of HIV-prevention
education programs for youth.
 Despite the decreases in live-birth rates and gonorrhea rates and 
the
increases in condom use, the findings in this report document that many
adolescents continue to be at risk for HIV infection, other STDs, and
unintended pregnancy because they engage in unprotected sexual 
intercourse.
Efforts to assist all adolescents in delaying first sexual intercourse 
and
increasing condom use among those who do engage in sexual intercourse 
must
be emphasized by health, education, and social service agencies and
providers.
 The data presented in this report and other data describing changes
in rates of pregnancy, abortion, live birth, and gonorrhea among
adolescents during the 1980s and 1990s have been summarized by state and
for the nation in a new CDC monograph**, Adolescent Health: State of the
Nation--Pregnancy, Sexually Transmitted Diseases, and Related Risk
Behaviors Among U.S. Adolescents (8).

References
1. Ventura SJ, Taffel SM, Mosher WD, Henshaw S. Trends in pregnancies 
and
pregnancy rates, United States, 1980-88. Hyattsville, Maryland: US
Department of Health and Human Services, Public Health Service, CDC, 
1992.
(Monthly vital statistics report; vol 41, no. 6, suppl).
2. Wasserheit J. Effect of changes in human ecology and behavior on
patterns of sexually transmitted diseases, including human 
immunodeficiency
virus infection. Proc Natl Acad Sci U S A 1994;91:2430-5.
3. Lindegren ML, Hanson C, Miller K, Byers RH Jr, Onorato I. 
Epidemiology
of human immunodeficiency virus infection in adolescents, United States.
Pediatr Infect Dis J 1994;13:525-35.
4. Kolbe LJ, Kann L, Collins JL. Overview of the Youth Risk Behavior
Surveillance System. Public Health Rep 1993;108(suppl 1):2-10.
5. Shah BV, Barnwell BG, Hunt PN, LaVange LM. SUDAAN user's manual, 
release
5.50. Research Triangle Park, North Carolina: Research Triangle 
Institute,
1991.
6. CDC. Premarital sexual experience among adolescent women--United 
States,
1970-1988. MMWR 1991;39:929-32.
7. NCHS. Advance report of final natality statistics, 1992. Hyattsville,
Maryland: US Department of Health and Human Services, Public Health
Service, CDC, 1994. (Monthly vital statistics report; vol 43, no. 5,
suppl).
8. CDC. Adolescent health: state of the nation--pregnancy, sexually
transmitted diseases, and related risk behaviors among U.S. adolescents.
Atlanta: US Department of Health and Human Services, Public Health 
Service,
1995; DHHS publication no. (CDC)099-4630.

* The YRBS was not conducted in 1992.
** Single copies of this document are available from CDC's Division of
Adolescent and School Health, National Center for Chronic Disease
Prevention and Health Promotion, Mailstop K-33, 4770 Buford Highway, NE,
Atlanta, GA 30341-3724; telephone (404) 488-5330.


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

To: hicnews

Update: Influenza Activity -- New York and United States, 1994-95 Season

 Influenza activity in the United States during the current 
influenza
season began in the Northeast, and during late January, spread to other
regions of the country. This report describes influenza outbreaks in
nursing homes in New York and summarizes national influenza surveillance
data from October 2, 1994, through February 11, 1995.

New York
 The first influenza outbreak reported to CDC during the 1994-95 
season
occurred in a 300-bed skilled-nursing facility in Long Island, New York.
On November 30, 1994, eight residents on one 20-bed corridor developed
influenza-like illness (ILI) (i.e., fever greater than or equal to 100 F
[greater than or equal to 38 C] and cough). On December 1, 
nasopharyngeal
swab specimens from these eight residents were submitted for rapid 
antigen
testing; within 5 hours after transport to the laboratory, influenza 
type
A was detected by enzyme immunoassay in six specimens. On the evening of
December 1, 293 of the 299 residents in the facility each received 100 
mg
of amantadine hydrochloride as treatment for the eight ill residents and
as prophylaxis against influenza A infection for the other 285 
residents.
Most (285 [95%]) residents had received influenza vaccine before the
outbreak. On December 2, as part of the nursing home's contingency plan 
for
influenza outbreaks, amantadine dosages were modified for individual
residents based on estimated creatinine clearance (1,2), and prophylaxis
was continued for 14 days. Other outbreak-control measures included
confining ill residents to their rooms for at least 72 hours after the
initiation of amantadine treatment and prophylaxis, confining all 
residents
to their individual units, suspending group activities, and minimizing 
the
assignment of nursing staff to multiple units. The amantadine dosage
subsequently was discontinued for five residents and reduced for 13
residents because of side effects (primarily confusion and agitation); 
for
most patients, side effects resolved within 48 hours of dosage 
adjustment.
 During the first 48 hours of amantadine prophylaxis and treatment, 
six
additional residents developed ILI. Of the 14 residents who developed
outbreak-associated ILI, five subsequently developed clinical pneumonia.
During the 2-week period of amantadine prophylaxis, sporadic cases of
febrile respiratory illness occurred in other units of the facility;
however, there was no clustering of cases.
 Tissue culture of all eight nasopharyngeal specimens yielded 
influenza
type A(H3N2). These isolates were further characterized at CDC; all were
antigenically similar to the A/Shangdong/09/93 strain included in the 
1994-
95 influenza vaccine.
 Influenza surveillance in New York state indicated increasing 
activity
beginning in late November 1994. From December 1, 1994, through February
11, 1995, outbreaks associated with influenza type A(H3N2) in 46 other
nursing homes were reported to the New York State Department of Health
(NYSDOH); of these, 16 were reported from nursing homes in Long Island. 
For
all 16 facilities, influenza type A infection was documented by rapid
antigen detection; in 13 facilities, amantadine was administered as an
outbreak-control measure. Outbreaks in five other nursing homes were 
caused
by influenza type B and, in two nursing homes, by influenza types A and 
B.
Based on findings of virologic surveillance in New York, influenza has
occurred in persons in all age groups during the 1994-95 season. Of the 
385
influenza virus isolates reported by laboratories in New York this 
season,
332 (86%) have been type A.

United States
 From November 27, 1994, through January 21, 1995, most influenza
activity was reported from the Northeast (3). However, during January 22-
February 11, regional or widespread activity was reported from states in
every region.
 Through February 11, World Health Organization collaborating
laboratories reported 1282 influenza virus isolates; of these, 923 (72%)
isolates have been type A and 359 (28%) have been type B. Of the 
influenza
A isolates that have been subtyped, all have been type A(H3N2).
 The proportion of deaths attributable to pneumonia and influenza
reported from 121 U.S. cities slightly exceeded the epidemic threshold
during six of the 19 weeks from October 2, 1994, through February 11, 
1995,
but has not exceeded the threshold for any 2 consecutive weeks.

Reported by: IH Gomolin, MD, Gurwin Jewish Geriatric Center, Commack, 
New
York; HB Leib, MS, RJ Gallo, S Kondracki, G Brady, G Birkhead, MD, DL
Morse, MD, State Epidemiologist, New York State Dept of Health.
Participating state and territorial epidemiologists and state public 
health
laboratory directors. World Health Organization collaborating 
laboratories.
Sentinel Physicians Influenza Surveillance System of the American 
Academy
of Family Physicians. WHO Collaborating Center for Surveillance,
Epidemiology, and Control of Influenza, Div of Viral and Rickettsial
Diseases, National Center for Infectious Diseases, CDC.

Editorial Note: Influenza vaccination is 70%-90% effective in preventing
ILI in young, healthy adults when the vaccine antigens closely match the
circulating influenza virus strains. Because of the decreased 
immunologic
response among the elderly, the vaccine is less effective in preventing 
the
occurrence of ILI in nursing home residents (i.e., 30%-40% effective) 
(4).
However, vaccination of nursing home residents is associated with a
substantial (i.e., 50%-60% effectiveness) reduction in the occurrence of
serious complications and hospitalization and with preventing death (up 
to
80% effective); in addition, vaccination reduces the risk for outbreaks 
in
nursing home settings (4,5). Antiviral agents are recommended as an 
adjunct
to vaccination in controlling influenza type A. To control influenza A
outbreaks in the nursing home setting, antiviral drugs should be
administered to all residents, regardless of influenza vaccination 
status.
 Influenza outbreak-control measures used in the New York nursing 
home
(e.g., rapid influenza A antigen detection and prompt initiation of
antiviral treatment and prophylaxis to all residents) were based on
recommendations of the Advisory Committee on Immunization Practices 
(ACIP)
(3,6) and CDC and are actively promoted by NYSDOH. Although annual
influenza vaccination of nursing home residents is considered a standard
of care, use of antiviral agents as an adjunct to vaccination is less
common, reflecting, in part, concern about side effects and, until
recently, the protracted time required for laboratory confirmation of
influenza type A.
 The use of amantadine as an adjunct for the control of influenza 
type
A outbreaks in New York during the current season illustrates the
usefulness of education about and promotion of the use of antiviral 
agents
and rapid influenza diagnostic methods. In September 1994, NYSDOH mailed
information to all health-care facilities in New York urging health-care
providers to administer vaccine in accordance with the recommendations 
of
the ACIP, to use rapid antigen-detection testing and viral culture when
institutional outbreaks of ILI are initially recognized, and to use
amantadine when appropriate. On December 20, the NYSDOH sent an 
electronic
mail message to these institutions to report the rapid identification of
influenza type A in the first nursing home outbreak and to reinforce the
recommendations for influenza control measures in health-care 
facilities.
 Recommendations of the ACIP for use of amantadine and rimantadine, 
the
two antiviral drugs currently available for treatment and prophylaxis of
influenza type A, were published in MMWR on December 30, 1994 (4). These
recommendations also provide information for assisting health-care
providers in selecting the appropriate drug for specific patient groups 
but
do not recommend preferential use of either drug.
 As influenza activity continues to increase in the United States,
health-care providers should be informed about findings of local, state,
and national influenza surveillance and be familiar with methods for 
rapid


 

(Continued from last message)
viral diagnosis. Updated information about national influenza 
surveillance
is available through the CDC Information System by voice or fax (404)
332-4551. In addition, providers should develop contingency plans to
control influenza outbreaks that include the use of rapid diagnosis. 
When
possible, policy decisions regarding use of amantadine and rimantadine
should be made before outbreaks occur.

References
1. Gomolin IH, Leib HB, Arden NH, Sherman FT. Control of influenza
outbreaks in the nursing home: guidelines for diagnosis and management. 
J
Am Geriatr Soc 1995;43:71-4.
2. ACIP. Prevention and control of influenza: part II, antiviral agents--
recommendations of the Advisory Committee on Immunization Practices 
(ACIP).
MMWR 1994;43(no. RR-15).
3. CDC. Update: influenza activity--United States, 1994-95 season. MMWR
1995;44:84-6.
4. Arden NH, Patriarca PA, Kendal AP. Experiences in the use and 
efficacy
of inactivated influenza vaccine in nursing homes. In: Kendal AP, 
Patriarca
PA, eds. Options for the control of influenza. New York: Alan R. Liss,
1986:155-68.
5. Patriarca PA, Weber JA, Parker RA, et al. Efficacy of influenza 
vaccine
in nursing homes: reduction in illness and complications during an
influenza A(H3N2) epidemic. JAMA 1985;253: 1136-9.
6. ACIP. Prevention and control of influenza: part I, vaccines--
recommendations of the Advisory Committee on Immunization Practices 
(ACIP).
MMWR 1994;43(no. RR-9).


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

To: hicnews
Counseling...

 Availability of Draft Recommendations for HIV Counseling and 
Testing
 for Pregnant Women

 CDC is requesting public review and comment on the draft document 
U.S.
Public Health Service Recommendations for HIV Counseling and Testing for
Pregnant Women. This document is available from the CDC National AIDS
Clearinghouse, P.O. Box 6003, Rockville, MD 20849-6003; telephone (800)
458-5231 or (301) 217-0023. Written comments must be received by April 
10,
1995, and should be mailed to CDC's Technical Information Activity,
Division of HIV/AIDS, Mailstop E-49, 1600 Clifton Road, NE, Atlanta, GA
30333; fax (404) 639-2007.


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

To: hicnews

 Erratum: Vol. 44, No. 5
 In the article "Update: AIDS Among Women--United States, 1994," on
page 81, the sentence beginning on the fourth line was incorrect. The
sentence should read, "Women with AIDS reported in 1994 represented 24% 
of
the cumulative total of 58,428 cases among women."


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

To: hicnews
...

 Exposure of Passengers and Flight Crew to Mycobacterium 
tuberculosis
 on Commercial Aircraft, 1992-1995

 From January 1993 through February 1995, CDC and state health
departments completed investigations of six instances in which 
passengers
or flight crew traveled on commercial aircraft while infectious with
tuberculosis (TB). All six of these investigations involved symptomatic 
TB
patients with acid-fast bacillus (AFB) smear-positive cavitary pulmonary
TB, who were highly infectious at the time of the flight(s). In two
instances, Mycobacterium tuberculosis isolated from the index patients 
was
resistant to both isoniazid and rifampin; organisms isolated from other
cases were susceptible to all antituberculous medications. In addition, 
in
two instances, the index patients were aware of their TB at the time of
travel and were in transit to the United States to obtain medical care.
However, in none of six instances were the airlines aware of the TB in
these passengers. This report summarizes the investigations by CDC and
state health departments and provides guidance about notification of
passengers and flight crew if an exposure to TB occurs during travel on
commercial aircraft.

 Investigation 1. A flight attendant had documented tuberculin skin 
test
(TST) conversion in 1989 but had not received preventive therapy (1). 
While
working on numerous domestic and international flights from May through
October 1992, she developed a progressively severe cough, and pulmonary 
TB
was diagnosed in November 1992. An investigation by CDC included TSTs of
212 flight crew who worked with the flight attendant from May through
October and 247 flight crew who had not been exposed to her. The 
prevalence
of positive TSTs among flight crew exposed to the flight attendant 
during
August through October was higher than among crew exposed from May 
through
June (25.6% versus 4.1%; p less than 0.01) and among unexposed flight 
crew
(1.6%; p less than 0.01). TST conversion was documented in two crew 
members
exposed only in August and October, respectively. TST positivity and
conversions were not associated with aircraft type, but were associated
with cumulative flight time exposure of greater than 12 hours. TST
reactivity was assessed in 59 passengers registered in the airline's
frequent flyer program who had traveled on flights worked by the flight
attendant with TB during August-October. Of these, four (6.7%) were TST
positive; all had traveled in October. The investigation indicated that 
the
index patient transmitted M. tuberculosis to other members of the flight
crew, but evidence of transmission to passengers was inconclusive (1).

 Investigation 2. During 1993, the Minnesota Department of Health
conducted an investigation of a foreign-born (i.e., born outside the 
United
States or Canada) passenger with pulmonary TB who traveled in the first
class section of an aircraft during a 9-hour flight from London to
Minneapolis in December 1992 (2). Of the 343 crew and passengers on the
aircraft, TST results were obtained for 59 (61%) of 97 U.S. citizens and
20 (8%) of 246 non-U.S. citizens. TSTs were positive for eight (10%)
persons--all of whom had received bacille Calmette-Guerin (BCG) vaccine 
or
had a history of past exposure to M. tuberculosis. The investigation
indicated no evidence of transmission of TB during the flight (2).

 Investigation 3. In March 1993, a foreign-born passenger with 
pulmonary
TB traveled on a 1/2-hour flight from Mexico to San Francisco. This
investigation included efforts by the San Francisco Department of Public
Health to obtain information by mail from all 92 passengers on the 
flight;
17 persons could not be contacted because of invalid addresses. TSTs 
were
positive in 10 (45%) of the 22 persons who were contacted and completed 
TST
screening; nine of these TST-positive persons were born outside the 
United
States. The other was a 75-year-old passenger who may have become 
infected
with M. tuberculosis while residing outside the United States or during 
a
period when TB was prevalent in the United States. The San Francisco
Department of Public Health found no conclusive evidence of transmission
during this flight.

 Investigation 4. In March 1993, CDC investigated a case of pulmonary
TB in a refugee who traveled on flights from Frankfurt, Germany, to New
York City (8-1/2 hours) and then to Cleveland, Ohio (1-1/2 hours) (3). 
Of
219 passengers and flight crew on both flights, 169 (77%) were U.S.
residents; 142 (84%) of the U.S. residents completed TST screening. TSTs
were positive in 32 (23%), including five persons who had converted from
negative on initial postexposure testing to positive on follow-up 
testing.
Of the 32 TST-positive persons, 29 had received BCG or were born and had
resided in countries where TB is endemic, including all five TST
converters. The five passengers who were TST converters had been seated 
in
sections throughout the plane. Because none of the U.S.-born passengers 
on
this flight had TST conversions, the investigation indicated that, 
although
transmission could not be excluded, the positive TSTs and conversions
probably were associated with prior M. tuberculosis infection, a boosted
immune response from prior exposure to TB, or prior BCG vaccination.

 Investigation 5. In March 1994, a U.S. citizen with pulmonary TB and
an underlying immune disorder who had resided long term in Asia traveled
on flights from Taiwan to Tokyo (3 hours), to Seattle (9 hours), to
Minneapolis (3 hours), and to Wisconsin (1/2 hour). Of 661 passengers on
these four flights, 345 (52%) were U.S. residents. The Wisconsin 
Division
of Health contacted the 345 U.S. residents and received reports about 
TST
results from 87 (25%) persons; of these, 14 (17%) had a positive TST. 
All
14 persons had been seated more than five rows away from the index 
patient;
nine of these persons had been born in Asia (including two with a known
prior positive TST). Of the five who were TST-positive and U.S.-born, 
one
was known to have had a positive TST previously, two had resided in a
country with increased endemic risk for TB, and two were aged greater 
than
or equal to 75 years. The investigation indicated that, although
transmission of TB during flights could not be excluded, the positive 
TSTs
may have resulted from prior M. tuberculosis infection.

 Investigation 6. In April 1994, a foreign-born passenger with 
pulmonary
TB traveled on flights from Honolulu to Chicago (7 hours, 50 minutes) 
and
to Baltimore (2 hours), where she lived with friends for 1 month. During
that month, her symptoms intensified; she returned to Hawaii by the same
route. Investigation in Baltimore determined that TST conversion had
occurred in the 22-month-old child of her friends. The four flights
included a total of 925 passengers and crew who were U.S. residents, of
whom 755 (82%) completed TST screening; of these, 713 (94%) were U.S.-
born.
The investigation by CDC indicated no evidence of transmission on the
flight from Honolulu to Chicago or the flight from Chicago to Baltimore.
Of the 113 persons who had traveled on the flight from Baltimore to
Chicago, TSTs were positive in three (3%), including two who were
foreign-born. However, of the 257 persons who traveled from Chicago to
Honolulu (8 hours, 38 minutes), TSTs were positive in 15 (6%), including
six who had converted; two of these six persons apparently had a boosted
immune response, while the other four had been seated in the same 
section
of the plane as the index patient. Because of TST conversions among
U.S.-born passengers, the investigation indicated that
passenger-to-passenger transmission of M. tuberculosis probably had
occurred.

Reported by: C Hickman, MPH, KL MacDonald, MD, MT Osterholm, PhD, State
Epidemiologist, Minnesota Dept of Health. GF Schecter, MD, TB Control
Program, San Francisco Dept of Public Health; S Royce, MD, DJ Vugia, MD,
Acting State Epidemiologist, California State Dept of Health Svcs. ME
Proctor, PhD, JP Davis, MD, State Epidemiologist for Communicable 
Diseases,
Bur of Public Health, Wisconsin Div of Health. S Bur, MPH, D Dwyer, MD,
Maryland Dept of Health and Mental Hygiene. Surveillance and 
Epidemiologic
Investigations Br, and Program Services Br, Div of Tuberculosis
Elimination, National Center for Prevention Svcs; Div of Field
Epidemiology, Epidemiology Program Office; Div of Quarantine, National
Center for Infectious Diseases, CDC.

Editorial Note: The investigations described in this report were 
undertaken
to determine whether exposure to persons with infectious pulmonary TB 
was
associated with transmission of M. tuberculosis to others traveling on 
the
same aircraft. Two of these investigations indicated that transmission
occurred (investigation 1, from flight attendant to other flight crew, 
and
investigation 6, from passenger to passenger). In investigation 6,
transmission occurred on the return to Hawaii, when the index passenger 
was
most symptomatic and on the longest flight. All persons with TST
conversions were seated in the same section of the aircraft as the index
passenger, suggesting that transmission was associated with seating
proximity. Because the origins of all foreign-born passengers were
countries in which TB is endemic and/or where BCG vaccine is routinely
used, TST results from these passengers do not reliably represent recent
infection. Among persons who could be contacted during the other
investigations, low response rates constrained the interpretation of
findings from those investigations.
 Investigations such as those described in this report are subject 
to
two substantial constraints. First, because the investigation may be
initiated several weeks to months following the time of the flight and
exposure, passengers may not be readily located. With the exception of
persons who are enrolled in frequent flyer programs, airline companies 
do
not routinely maintain residence addresses or telephone numbers for
passengers. Second, the time elapsed between the flight and when public
health authorities and airline companies become aware of an exposure and
when passengers are notified and tested limits the use of TSTs to assess
for conversion. To interpret prevalent positive TST results, other 
possible
reasons for a positive TST result must be considered, including prior
exposure to TB, residence or birth in countries in which TB is endemic, 
and
BCG vaccination. In the United States, an estimated 4%-6% of the total
population is TST positive (4), and in developing countries, the 
estimated
prevalence of M. tuberculosis infection ranges from 19.4% (in the 
Eastern
Mediterranean region) to 43.8% (in the Western Pacific region) (5).
 To prevent exposures to TB aboard aircraft, when travel is 
necessary,
persons known to have infectious TB should travel by private 
transportation
(i.e., not by commercial aircraft or other commercial carrier). In
addition, patients with infectious TB should at least be sputum
smear-negative for AFB before being placed in indoor environments 
conducive
to transmission (6). Three negative sputum smear examinations of 
specimens
on separate days in a person on effective anti-TB therapy indicate an
extremely low potential for transmission, and a negative culture 
virtually
precludes potential for transmission (6). Decisions about a TB patient's
infectiousness and ability to travel should be made on an individual 
basis.
 The risk for M. tuberculosis transmission on an aircraft does not
appear to be greater than in other confined spaces. Based on a
consideration of current evidence indicating low risk for transmission 
of
TB on aircraft, need for notification of passengers and flight crew 
members
may be guided by three criteria. First, the person with TB was 
infectious
at the time of the flight. Persons who, at the time of flight, are
symptomatic with AFB smear-positive, cavitary pulmonary TB or laryngeal 
TB
are most likely to be infectious. Evidence of transmission to household 
and
other close contacts also indicates infectiousness. Second, exposure was
prolonged (e.g., duration of flight exceeded 8 hours). Third, priority
should be given to notifying passengers and flight crew who were at
greatest risk for exposure based on proximity to the index passenger 
(for
example, depending on the aircraft design, proximity may be defined as
seating or working in the same cabin section as the infected passenger).
Notification should be conducted by the airline in coordination with 
local
and state TB-control programs.

References
1. Driver CR, Valway SE, Morgan WM, Onorato IM, Castro KG. Transmission 
of
M. tuberculosis associated with air travel. JAMA 1994;272:1031-5.
2. McFarland JW, Hickman C, Osterholm MT, MacDonald KL. Exposure to
Mycobacterium tuberculosis during air travel. Lancet 1993;342:112-3.
3. Miller MA, Valway SE, Onorato IM. Assessing tuberculin skin test
conversion after exposure to tuberculosis on airplanes [Abstract]. In:
Program and abstracts of the annual meeting of the American Public 
Health
Association. San Francisco: American Public Health Association, 1993.
4. CDC. National action plan to combat multidrug-resistant tuberculosis.
MMWR 1992;41(no. RR-11):1-48.
5. Sudre P, ten Dam G, Kochi A. Tuberculosis: a global overview of the
situation today. Bull World Health Organ 1992;70:149-59.
6. American Thoracic Society. Control of tuberculosis in the United 
States.
Am Rev Respir Dis 1992;146:1623-33.


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End of HICNet Medical News Digest V08 Issue #06
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