Tracing air travelers at risk for disease still tough

Jun 10, 2008 (CIDRAP News) – Five years after the SARS (severe acute respiratory syndrome) epidemic spread around the globe via air travel, significant barriers still stand in the way of tracking down and notifying airline passengers who may have been exposed to an infectious disease.

The process for contacting those passengers is complex, involving a mix of international, national, state, and local government agencies as well as private businesses. Studies conducted recently by staff at the US Centers for Disease Control and Prevention (CDC) and the Public Health Agency of Canada suggest that the process is not working well. And interviews with public health and air-travel experts confirm that there are jurisdictional and data-access challenges to tracing and alerting passengers.

Meanwhile, additional regulatory authority that could improve the flow of passenger data from airlines to public-health agencies has been stalled in public-comment revisions since mid-2006, though the CDC says it hopes to complete the revisions this year.

Research shows difficulties
The studies were presented at the International Conference on Emerging Infectious Diseases, a biennial conference that took place in Atlanta in April, but have not otherwise been published. They both focused on tracking passengers who may have been exposed to tuberculosis, a situation that presents particular challenges because people are likely to be infectious for a while before being diagnosed and thus may expose others before they know their own status.

Under regulations composed by the World Health Organization, passengers are considered at risk for contracting tuberculosis if they sit within two rows fore or aft of a contagious passenger for 8 hours or more (while flying or during a ground delay), a standard that is supported by a meta-analysis published in The Lancet in 2005.

Most flights of that length cross international borders, which greatly complicates contacting passengers, according to a study by Dr. Derek Scholten of the Public Health Agency of Canada and Dr. Karen Marienau, a medical officer with the CDC's Division of Global Migration and Quarantine. They interviewed participants in 130 contact-tracing investigations conducted by the United States and Canada in 2006 and 2007.

"Let's say we have someone who came into the United States from Paris on Air France, was in the U.S. for a few weeks and then returned to France, and is discovered to have been infectious on both inbound and outbound flights," Marienau said in an interview. "We would want to notify US citizens that were on that outbound flight, but we have to rely on French authorities contacting Air France and initiating the investigation."

A second study conducted by Marienau and five colleagues from the CDC's airport quarantine stations demonstrated that contact tracing within the United States also faces challenges. They looked at the results of 68 investigations of TB exposure on airlines carried out in the United States in the first 11 months of 2007, involving 2,062 passengers.

Under the rules governing interaction among federal, state and local agencies, passenger contact information flows from the airline to the CDC, through a state health agency and to a local health department that is responsible for tracking down passengers in their jurisdictions; local agencies are then supposed to tell the CDC their results.

The local health agencies that pursued the investigations in Marienau's study told the CDC that no contact information at all was available for 23% (478) of the passengers. And it is not clear how reliable the information provided for the other 77% was, because 88% of the 2,062 passengers who were potentially exposed were never tested for TB. (About 10% [211] took a TB test, and about 2% [38] were able to prove to investigators that they already knew their TB status.)

Not enough information came back from local health departments to indicate whether potential contacts were found and declined to be tested, or could not be found, Marienau said. While the study reveals problems in communication between local health agencies and the CDC, it also suggests that "despite our best efforts we are not getting complete or accurate locator information," she said.

Formal CDC request needed
How much information airlines collect from passengers and how fast they can pass it on are longstanding sore points with the CDC. The agency has legal authority to request passenger identity and whatever contact information the airlines possess via a mechanism called a "manifest order," a form letter signed by the CDC's director and sent to an airline by e-mail or fax.

"We can't release anything until we have the formal request from the CDC because of privacy issues," Barbara Martin, a registered nurse on Delta Airlines' medical team, said in an interview. "We can certify the index case was on a particular flight on a particular date, but beyond that, we can't tender information" until the manifest order is received, she said.

But putting together the information for legal release poses significant challenges. Airlines, Martin said, often don't have complete contact information for passengers. The amount of data available depends on how direct the customer relationship is. A member of an airline's frequent-flyer program will already have provided abundant information directly to the airline. However, someone who bought a ticket through an online discounter may have given that information only to the discounter, not to the airline as well. Traditional travel agents may supply their own contact information, rather than the passenger's; the same goes for corporate travel departments. Foreign travel agents may supply only a name and passport number.

In addition, whatever information flows through those channels tends to be home or business contact information. Very few passengers think to provide airlines with itinerary details. One location where a passenger intends to stay is usually demanded by immigration authorities for admittance to a country; but because it is collected by a different agency, sometimes one belonging to a different government, airlines cannot access it easily.

Plus, all the information on a passenger is not stored in a single place. A flight manifest may contain name, flight number, date, and seat number—but any additional contact information resides in other systems. That is both for privacy reasons and because the costs of storing the manifest plus all the contact data for every flight every day would be enormous, said Katherine Andrus, assistant general counsel at the Air Transport Association.

Proposed changes stir controversy
The CDC has attempted to influence what information airlines collect and how it is stored and delivered, but has not succeeded so far. In November 2005, within a broad "notice of proposed rulemaking" on communicable-disease control, it proposed several changes to the federal regulations governing passenger data (42 CFR parts 70.4 and 70.5). It asked that airlines operating interstate flights out of certain airports be required to request contact information from passengers, maintain it in a database linked to the flight manifest for 60 days after the flight, and transmit it to the CDC electronically within 12 hours of a manifest order.

The proposal was controversial. Airlines charged that the database would infringe on customer privacy, and also said it would duplicate data storage that they maintain to satisfy Department of Homeland Security requirements. (Airlines are required to transmit names and passport numbers to DHS before international flights depart.)

In public comments on the rule change, the University of Pittsburgh Medical Center's (UPMC's) Center for Biosecurity—a think tank co-founded by the former leader of the WHO's smallpox-eradication effort—strongly opposed the additional data collection, saying: "It will cause legitimate public concern that government would be able to track citizens' movements and have access to their personal information based on the suspicion of a person's having a contagious illness or having had contact with someone who had a contagious illness."

However, in June 2004, the Project on the Public and Biological Security at the Harvard School of Public Health found that Americans are willing to give up some data privacy in exchange for enhanced protection against contagion. The project polled 1,006 adults (including 633 who said they took at least one flight within the United States per year and 240 who said they took at least one cross-border flight per year) and found that 94% would want to be contacted if they might have been exposed to a serious contagious disease on an airplane.

Among the international travelers, 88% said they would be willing to give the airline their cell phone or pager number or e-mail address, and 73% said they would be willing to provide details of their destinations. Among the domestic fliers, 93% said they would be willing to provide contact information. However, they did expect the data to be protected: 37% of domestic passengers and 38% of international fliers said they were "very concerned" their privacy might be breached.

The poll results are paradoxical. According to airlines and the CDC, there is a wide gap between the proportion of passengers who said they would want to be contacted and the number who now provide contact information. The Harvard poll suggests why: Passengers think it is already available. Half of the international passengers and 52% of the domestic fliers said they thought public health authorities would be able to access emergency-contact information quickly if needed.

In the 15 months since public comment on the proposed rule closed, the CDC has been negotiating with the airlines and DHS over how much of the data collected for security purposes could also be used for public-health tracking if necessary. Ten out of 13 pieces of information needed for contact investigations are already gathered by DHS and could be shared between agencies, placing a smaller data-delivery burden on the airlines, Dr. Martin Cetron, director of the CDC's quarantine division, said in an interview. A final rule is expected by the end of 2008.

See also:

WHO "Tuberculosis and Air Travel" guidelines, 2006

Mangili A, Gendreau MA. Transmission of infectious diseases during commercial air travel. Lancet 2005 Mar 12;365(9463):989-96 [Abstract]

SJ Olsen, HL Chang, TY Cheung, et al. Transmission of severe acute respiratory syndrome on aircraft. N Engl J Med 2003 Dec 18;349(25):2416–22 [Full text]

CDC's 2005 proposal for changes in rule governing airline passenger data (see pages 8-10, parts 70.4 and 70.5)

Nov 22, 2005, CIDRAP News story "CDC updating disease-control rules affecting travelers"

Poll results from the Project on the Public and Biological Security, Harvard School of Public Health

Studies presented at the International Conference on Emerging Infectious Diseases, April 2008 (246 pages); see abstracts listed below
Scholten D, et al. Challenges to contact tracing investigations following international airline travel by persons with infectious tuberculosis, pp 187-8
Marienau KJ, et al. Exposure to infectious tuberculosis (TB) during air travel: outcome of passenger contact investigations initiated June-October 2007, p 206 (Note: Numbers listed in the abstract were changed after accumulation of more data), p 206

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