And the Air-Travel Risks Just Keep on Comin': This Time, Measles

Tomorrow's issue of the MMWR reports on the multistate outbreak of documented measles cases related to the travel of an infected 12-year-old Japanese baseball player to the 2007 Little League World Series in Williamsport, Pennsylvania. The boy, whose vaccination status was unknown, flew on an international flight from Japan to Detroit and then on a domestic flight from Detroit to Baltimore on August 13, after acquiring the infection from his brother in Japan. Subsequent, documented transmissions of measles from this index case (1) are outlined below.

Case 2: Another 12-year-old Japanese boy was in contact with the index case in Japan on August 12. He arrived in the United States on August 15 and attended the World Series as a spectator; he first became ill August 20.

Case 3: A 53-year-old woman, who sat in front of the index case on the domestic flight from Detroit to Baltimore, became ill with measles on August 25.

Case 4: A 25-year-old federal airport officer, who worked in the customs area of the Detroit airport on August 13, first developed measles symptoms on August 23. He had no documented history of measles vaccination.*

Case 5: A 40-year-old corporate sales rep met the index case on August 14 in Pennsylvania and developed measles symptoms on August 26. He had no documented measles vaccination.

Case 6: An 18-year-old college student attended a sales event in Texas with the 40-year-old rep on August 20. Despite having previously received 2 doses of MMR vaccine, he developed symptoms on September 9.

Case 7: A 19-year-old college student, the roommate of case 6, attended the same sales event of the 40-year-old rep on August 20. He also had a history of receiving 2 MMR vaccine doses but developed symptoms on September 10.

According to the MMWR, the viral genotype from the index case was identical to the genotypes obtained from cases 2, 3, 5, 6, and 7. (Amplification attempts to genotype case 4 were unsuccessful.) The report provides a useful graphic, which illustrates the chain of measles transmission, and reinforces the importance of vaccination regardless of travel history. While 2 doses of measles vaccine are reportedly 99% effective, the disease remains possible in those persons who have been vaccinated (namely, cases 6 and 7). The report also emphasizes that those individuals who were born before 1957—before the institution of routine MMR vaccination during childhood—may be susceptible to infection (eg, case 3). 

Although all of the affected individuals recovered, measles is not necessarily a benign illness. The 40-year-old rep required hospitalization for high fever and pneumonia and experienced an epileptic fit, according to the report. Widely reported is the statistic that approximately 1 measles case in 1000 is associated with the development of encephalitis.

*A coworker of the officer developed measles approximately 1 month later; however, it is unclear if this case is related to case 4, either directly or indirectly. (The typical incubation period for measles is 7-18 days.)