Flight related tuberculosis contact investigations in the United States: comparative risk and economic analysis of alternate protocols.

BACKGROUND: In-flight transmission risk of Mycobacterium tuberculosis is not well defined, although studies suggest it is low. The impact of flight-related tuberculosis (TB) contact investigations (TBCIs) on TB prevention and control is not well established, and they compete for resources with activities with established benefits. We sought to determine the risks and cost-benefits of using more restrictive criteria in comparison to the Centers for Disease Control and Prevention (CDC) 2008 protocol for TBCIs. METHODS: The risk-benefits of a modified CDC protocol were analyzed in comparison to the 2008 CDC protocol using data from flight-related TBCIs conducted in the United States from 2007 through 2009. We predicted the numbers and characteristics of case-travelers that would be identified using each protocol's criteria, and results of the associated passenger-contacts' TB screening tests. The economic analysis compared the costs of TBCIs to avoided costs of TB treatment and mortality using a Return on Investment model. RESULTS: The estimated in-flight transmission risk using a modified CDC protocol was 1.4%-19% versus 1.1%-24% for the 2008 protocol. Numbers of TBCIs and immediate costs to health departments were reduced by half. Long-term cost-benefits were comparable. CONCLUSIONS: CDC's modified protocol appears to be a feasible alternative that will conserve public health resources without jeopardizing the public's health.

Economics of United States tuberculosis airline contact investigation policies: a return on investment analysis.

BACKGROUND: In 2011, the Centers for Disease Control and Prevention modified its 2008 protocol for flight-related tuberculosis contact investigation initiation. The 2011 Modified protocol was implemented and replaced the 2008 CDC protocol based on comparative epidemiologic and economic analyses; this publication reports the economic analysis results. METHODS: A return on investment model compared relative changes in tuberculosis disease treatment costs resulting from expenditures on tuberculosis contact investigations and latent tuberculosis infection treatment for the 2008 CDC and Modified protocols. RESULTS: At moderate/high rates of latent tuberculosis infection and tuberculosis disease, positive returns on investment indicated each $1.00 spent on tuberculosis contact investigations and latent tuberculosis treatment resulted in more than $1.00 of savings from reduced tuberculosis disease treatment costs. Low rates of latent tuberculosis infection and tuberculosis disease resulted in negative returns on investment, indicating economic losses from tuberculosis disease treatment costs. There were smaller economic losses at low latent tuberculosis infection and tuberculosis disease rates with the Modified protocol in comparison to the 2008 CDC protocol, while both identified comparable numbers of persons at risk for tuberculosis. CONCLUSION: The Modified protocol for conducting flight-related tuberculosis contact investigations represents a better use of resources and protects public health.

Measles transmission during air travel, United States, December 1, 2008-December 31, 2011.

BACKGROUND: Flight-related measles contact investigations in the United States are coordinated by the Centers for Disease Control and Prevention (CDC). To evaluate the efficiency of CDC's measles protocol, we analyzed data from contact investigations conducted December 2008-December 2011. METHODS: Cases were defined as travelers diagnosed with measles that were infectious at the time of the flight. Passengers seated within 2 rows of the case-traveler and all babies-in-arms were defined as contacts. Contact information obtained from airlines was distributed to US health departments; reporting of outcomes was requested. We cross-referenced the National Notifiable Diseases Surveillance System and CDC's National Center for Immunization and Respiratory Diseases to identify unreported cases in passenger-contacts and in passengers not identified as contacts. RESULTS: Our evaluation included 74 case-travelers on 108 flights. Information for 2673 (79%) of 3399 passenger-contacts was provided to health departments; 9 cases of secondary measles were reported. No additional cases were identified. CONCLUSION: Our evaluation provided evidence of measles transmission related to air travel. CDC's protocol efficiently identifies passengers most at risk of exposure and infection for flights into and within the United States.

Influenza A(H1N1)pdm09 during air travel.

The global spread of the influenza A(H1N1)pdm09 virus (pH1N1) associated with travelers from North America during the onset of the 2009 pandemic demonstrates the central role of international air travel in virus migration. To characterize risk factors for pH1N1 transmission during air travel, we investigated travelers and airline employees from four North American flights carrying ill travelers with confirmed pH1N1 infection. Of 392 passengers and crew identified, information was available for 290 (74%) passengers were interviewed. Overall attack rates for acute respiratory infection and influenza-like illness 1-7 days after travel were 5.2% and 2.4% respectively. Of 43 individuals that provided sera, 4 (9.3%) tested positive for pH1N1 antibodies, including 3 with serologic evidence of asymptomatic infection. Investigation of novel influenza aboard aircraft may be instructive. However, beyond the initial outbreak phase, it may compete with community-based mitigation activities, and interpretation of findings will be difficult in the context of established community transmission.

No evidence of mumps transmission during air travel, United States, November 1, 2006-October 31, 2010.

Since November 2006, flight-related mumps contact investigations were conducted in the United States only for flights ≥5 h long after an investigation showed minimal risk of mumps transmission on flights <5 h. Because the transmission risk on longer flights had not been evaluated, we investigated whether there was evidence to support the guidelines. We examined data from mumps contact investigations that were initiated by the US Centers for Disease Control and Prevention (CDC) from November 2006 to October 2010. We also cross-referenced passenger-contact data with data on mumps cases in the National Notifiable Diseases Surveillance System (NNDSS). Twenty-seven cases met inclusion criteria. Of 246 passengers identified as contacts, 166 (67%) were distributed to a US health department for contact tracing. Outcomes were reported for 21 (13%) of those 166 passengers. No secondary cases of mumps among passenger contacts were reported or identified by cross-referencing NNDSS data. The findings suggested that in-flight risk of mumps transmission is not high. Furthermore, these investigations have low yield, are resource intensive, there is no post-exposure prophylaxis, and mumps transmission has not been eliminated in the United States. Therefore, CDC discontinued conducting flight-related mumps contact investigations in May 2011.

Rubella contact tracing associated with air travel.

This report reviews U.S. guidelines for the identification of persons exposed to rubella during air travel. In response to an individual with rubella who traveled on multiple flights, CDC conducted an airline contact investigation that was expanded beyond customary protocol to assess if current operating procedures are adequate. Of 250 potentially exposed airline passengers, 215 (86%) were contacted and none developed a rubella-like rash, arguing against the need to notify passengers beyond the standard protocol in most cases.

Tuberculosis investigations associated with air travel: U. S. Centers for Disease Control and Prevention, January 2007-June 2008.

INTRODUCTION: Contact investigations conducted in the United States of persons with tuberculosis (TB) who traveled by air while infectious have increased. However, data about transmission risks of Mycobacterium tuberculosis on aircraft are limited. METHODS: We analyzed data on index TB cases and passenger contacts from contact investigations initiated by the U.S. Centers for Disease Control and Prevention from January 2007 through June 2008. RESULTS: Contact investigations for 131 index cases met study inclusion criteria, including 4550 passenger contacts. U.S. health departments reported TB screening test results for 758 (22%) of assigned contacts; 182 (24%) had positive results. Of the 142 passenger contacts with positive TB test results with information about risk factors for prior TB infection, 130 (92%) had at least one risk factor and 12 (8%) had no risk factors. Positive TB test results were significantly associated with risk factors for prior TB infection (OR 23; p<0.001). No cases of TB disease among passenger contacts were reported. CONCLUSION: The risks of M. tuberculosis transmission during air travel remain difficult to quantify. Definitive assessment of transmission risks during flights and determination of the effectiveness of contact-tracing efforts will require comprehensive cohort studies.

Three air travel-related contact investigations associated with infectious tuberculosis, 2007-2008.

BACKGROUND: The potential for transmission of Mycobacterium tuberculosis during air travel has garnered considerable attention in the media and among public health authorities due to high-profile cases of international travelers with infectious tuberculosis (TB). METHODS: During 2007 and 2008, state and local health officials were asked to locate and conduct diagnostic follow-up for airline passengers considered contacts of three travelers, two with multidrug-resistant (MDR) TB and one considered highly contagious, who undertook air travel while infectious with TB disease. RESULTS: Public health departments in 21 states located and evaluated 79 (60%) of the 131 passenger contacts identified; 52 (40%) were lost to follow-up. Eight (10%) contacts had a history of TB disease or latent TB infection and were not retested. Sixteen (23%) of 71 contacts tested had positive TB test results suggesting latent TB infection, 15 of whom were from countries reporting estimated TB disease rates of greater than 200 cases/100,000 persons. CONCLUSIONS: Passenger contacts' positive test results may represent prior TB infection acquired in their countries of residence or may be a result of new TB infection resulting from exposure during air travel.

Laboratory diagnosis of two scrub typhus outbreaks at Camp Fuji, Japan in 2000 and 2001 by enzyme-linked immunosorbent assay, rapid flow assay, and Western blot assay using outer membrane 56-kD recombinant proteins.

Two scrub typhus outbreaks occurred among U.S. Marines training at Camp Fuji, Japan, between October 25 and November 3, 2000 and October 17 and November 30, 2001. Nine cases in approximately 800 Marines in 2000 and eight cases in approximately 900 Marines in 2001 (approximate attack rates = 1.1% and 0.9%, respectively) reported with signs and symptoms of fever, rash, headache, lymphadenopathy, myalgia, and eschar. Serologies and rapid response to doxycycline treatment indicated they had scrub typhus. Sixty-four convalescent serum samples (18 suspected cases and 46 negative controls) from U.S. Marines training at Camp Fuji during the outbreaks were assessed by enzyme-linked immunosorbent assay (ELISA), rapid flow assay (RFA), and Western blot assay for evidence of infection with Orientia tsutsugamushi, the causative agent of scrub typhus. All but one suspected case had serologic evidence of scrub typhus and all 46 control sera were non-reactive to O. tsutsugamushi antigens. The recombinant 56-kD antigen (r56) from the Karp, Kato and Gilliam strains of O. tsutsugamushi in an ELISA format provided better results than Karp r56 alone (ELISA and RFA) or whole cell antigen preparation from Karp, Kato and Gilliam (ELISA).