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Letter
SARS Transmission and Commercial
Aircraft
J. Gabrielle Breugelmans,* Phillip Zucs,* Klaudia Porten,* Susanne
Broll,* Matthias Niedrig,* Andrea Ammon,* and Gérard Krause*![Comments](https://webarchive.library.unt.edu/eot2008/20081018142537im_/http://cdc.gov/ncidod/eid/images/email.gif)
*Robert Koch-Institut, Berlin, Germany
Suggested citation
for this article:
Breugelmans JG, Zucs P, Porten K, Broll S, Niedrig M, Ammon A, et al.
SARS transmission and commercial aircraft [letter]. Emerg Infect Dis
[serial on the Internet]. 2004 Aug [date cited]. Available from:
http://www.cdc.gov/ncidod/EID/vol10no8/04-0093.htm
To the Editor: Severe acute respiratory syndrome (SARS) is an
emerging transmissible disease first reported in Asia in February 2003.
The disease is characterized by acute onset of fever with nonproductive
cough, myalgia, shortness of breath, or difficulty breathing (1).
Approximately 14% of case-patients require mechanical ventilation (1,2).
The syndrome is caused by the previously unrecognized SARS-associated
coronavirus (SARS-CoV) (3). The primary mode of SARS
transmission is through close person-to-person contact. In March 2003,
the World Health Organization (WHO) issued two travel advisories to SARS-affected
countries. Despite these advisories, probable case-patients traveled by
air internationally, thereby spreading the disease globally. The extent
of risk posed by probable cases for in-flight transmission of SARS is
unclear.
A study was conducted by the Robert Koch Institute in Berlin, Germany,
to document SARS transmission during international flights. On April 11,
2003, the Institute was notified that a probable SARS-infected person
had flown from Hong Kong to Frankfurt, Germany, on March 30 to 31, 2003,
and then traveled extensively in Europe after onset of symptoms. In 5
days, the traveler, a 48-year-old Hong Kong businessman, had flown on
seven flights throughout Europe (Table). On March
31, symptoms of SARS, including fever and general malaise developed; whether
he had a cough at this time is unclear. He was admitted to a hospital
in Hong Kong on April 8, and mechanical ventilation was initiated. He
was reported to WHO as a suspected SARS patient on April 9 and diagnosed
with SARS on April 10. Polymerase chain reaction analysis conducted on
the patient's nasopharyngeal aspirate showed positive results for SARS-CoV
on April 14.
Passenger manifests from the seven flights on which the patient had flown
were requested by the local health departments and the Institute. In a
previous study, Kenyon et al. indicated that airline passengers seated
within two rows of an infectious tuberculosis patient were at greatest
risk for infection (4). To determine an association between
seating proximity to the SARS patient and transmission of SARS, a study
that included all airline passengers seated within four rows (i.e., front,
back, and same row) of the index patient (4) was conducted.
Passengers >18 years of age who lived in Germany were contacted
by the Institute and asked to participate in the study; all participants
gave informed consent for inclusion in the study. Passengers in other
countries were not included in the study because contact information was
not available. Passengers <18 years of age were not included in the
study; ethical approval from an Institutional Review Board, which would
have delayed the study, would have been necessary. Contact information
for study participants was forwarded to local health departments so that
public health officials could provide follow-up care. Study participants
were interviewed approximately 3 months after their flights because contact
information was not available earlier. A standardized questionnaire was
developed to collect information on demographics, flight details, countries
visited before the flights, use of mask, and symptoms. Furthermore, 5–10
mL of whole blood was drawn and tested for SARS-CoV antibodies by using
immunofluorescence assay.
A total of 250 passengers were identified and selected for the study.
Contact information was available for 109 passengers; 69 of the 109 were
living in Germany. Sixty-two of those 69 passengers were contacted, and
41 passengers agreed to participate in the study. Thirty-six participants
completed questionnaires and had blood samples taken. The male-to-female
ratio was 3:5, and the median age was 41 years (25–59 years). Contact
information was not available for five passengers, which made their inclusion
in the study impossible. All serologic samples (N = 36) tested were negative
for SARS-CoV immunoglobulin G antibodies, and none of the 36 passengers
reported symptoms characteristic of SARS. Ten passengers complained of
cough, headache, and muscle aches. One passenger reported a cough, muscle
aches, and fever, but symptoms started 10 days after the flight. An analysis
of the seating arrangement showed that the study participants were randomly
distributed around the index patient.
No SARS transmission was shown among contacted passengers seated in close
proximity to the index patient; these results suggest that in-flight transmission
of SARS is not common. These results are consistent with other studies
that assessed the risk for in-flight transmission of SARS (5,6).
The results also suggest that SARS-CoV is not efficiently transmitted,
as reflected in its basic reproduction number R0 (range 2–4)
(7). The SARS-infected patient on the indicated flights
was in his first week of illness; infectivity is greatest in the second
week (8). Therefore, the likelihood of SARS transmission
on the indicated flights was not high. These results are further supported
by the fact that all contacts were asymptomatic 13 days after their last
contact with the SARS patient. No information was available on healthcare
contacts. Although we did not observe any SARS transmission, we cannot
rule out the possibility that it may have occurred. We had no contact
information on 56% of the passengers on the indicated flights and, therefore,
had to exclude them from the investigation. Obtaining complete contact
information from the remaining passengers was difficult, which severely
impeded the investigation. Similarly, we were unable to contact crew members
and had to exclude them. Recent studies have documented SARS transmission
to passengers seated more than four rows away from an index patient (5,9);
thus, studying the passenger proximity to the patient may not be sufficient.
Because of these limitations, our final sample size was small and probably
biased. Since we did not observe any evidence to indicate in-flight transmission
of SARS, we were unable to assess the importance of seat assignment proximity
as a risk factor.
The study shows that the roles of public health authorities and the aviation
industry should be to "harmonise the protection of public health
without the need to avoid unnecessary disruption of trade and travel"
in public health emergencies such as global SARS transmission (10).
We recommend strengthening the collaboration between national health authorities
and the airline industry. Furthermore, the International Air Transport
Association should establish procedures to ensure that complete contact
information is available for all passengers and that rapid notification
can be accomplished in case of potential exposure to infectious diseases.
Acknowledgments
We thank René
Gottschalk and Angela Wirtz for supporting negotiations with the airline;
Bettina Supthut for data collection on all study participants in Munich,
Germany; and the staff of participating state local health departments
Germany and all participating airline passengers.
The Robert Koch
Institute supported this investigation. At the time of the study, all
authors were employed by this institute.
References
- Booth CM, Matukas LM, Tomlinson GA, Rachlis AR, Rose
DB, Dwosh HA, et al. Clinical
features and short-term outcomes of 144 patients with SARS in the greater
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S, et al. Identification
of a novel coronavirus in patients with severe acute respiratory syndrome.
N Engl J Med. 2003;348:1967–76.
- Kenyon TA, Valway SE, Ihle WW, Onorato IM, Castro KG. Transmission
of multidrug-resistant Mycobacterium tuberculosis during a long
airplane flight. N Engl J Med. 1996;334:933–8.
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Table.
Flight itinerary of SARS patienta |
|
Departure city
|
Arrival city
|
Date/time departure
|
Date/time arrival
|
Duration (h:min)
|
|
Hong Kong
|
Frankfurt
|
March 30/23:10
|
March 31/05:35
|
12:25
|
Frankfurt
|
Barcelona
|
March 31/09:05
|
March 31/11:10
|
2:05
|
Onset of symptoms after arrival in Barcelona on
March 31, 2003
|
Barcelona
|
Frankfurt
|
April 2/07:05
|
April 2/09:15
|
2:10
|
Frankfurt
|
London
|
April 2/10:15
|
April 2/11:30
|
2:15
|
London
|
Munich
|
April 3/15:25
|
April 3/18:10
|
1:45
|
Munich
|
Frankfurt
|
April 4/14:50
|
April 4/16:00
|
1:10
|
Frankfurt
|
Hong Kong
|
April 4/17:40
|
April 5/10:35
|
9:55
|
|
aSARS, severe acute respiratory
syndrome. |
|