The Centers for Disease Control and Prevention (CDC) is investigating an outbreak of mumps that began in Iowa in December 2005. As of April 10, 2006, more than 500 possible cases had been reported in Iowa, and other cases that were thought to be linked to the Iowa outbreak were being investigated in Illinois, Kansas, Minnesota, Missouri, Nebraska, and Wisconsin.

Two persons who were diagnosed with mumps and were potentially infectious traveled on Northwest Airlines and American Airlines flights between March 26 and April 2, 2006. The full CDC report contains a complete list of flights and is available online athttp://www.cdc.gov/mmwr/preview/mmwrhtml/mm55d411a1.htm?s_cid=mm55d411a1_e.

Mumps is characterized by a nonspecific prodrome, including myalgia, anorexia, malaise, headache, and fever, followed by acute onset of unilateral or bilateral tender swelling of parotid or other salivary glands. An estimated 60 to 70 percent of mumps infections produce typical acute parotitis. Approximately 20 percent of infections are asymptomatic, and nearly 50 percent are associated with nonspecific or primarily respiratory symptoms. Complications include orchitis, oophoritis, mastitis, meningitis, encephalitis, spontaneous abortion, and deafness. Transmission occurs by direct contact with respiratory droplets or saliva. The incubation period is 14 to 18 days, and the infectious period is from three days before symptom onset until nine days after symptom onset.

The risk for transmission of respiratory infectious diseases during air travel may depend on several factors, including immunity of passengers, infectiousness of the organism, degree of shedding of the pathogen by infectious passengers, hygienic practices of infectious passengers, proximity of others to infectious passengers, hygienic practices of the other passengers and flight crew, flight duration, and cabin environment of the aircraft. Although exposure and transmission of mumps during commercial air travel has not been described previously, transmission of other respiratory pathogens during air travel has been reported.