Role of Nosocomial Transmission in a Measles Outbreak — Arizona, 2008

Background:
Due to high measles vaccination coverage levels, measles elimination was declared in the U.S. in 2000. However, measles importations continue and can lead to outbreaks, mostly in community settings. On February 12, a visiting Swiss National was admitted to Hospital A with rash and pneumonia. Measles was confirmed on February 19. Through July 21st, 13 additional measles cases were identified, many in healthcare settings.

Objectives:
We sought to determine factors contributing to this nosocomial outbreak.

Methods:
We classified measles cases according to the CDC/CSTE case definitions. We defined healthcare settings (HS) as locations that provided medical care and healthcare personnel (HCP) as persons who worked in healthcare settings.

Results:
The 14 confirmed measles case-patients ranged in age from 8 months to 50 years; five (36%) were hospitalized. All 14 case-patients were unvaccinated; seven (50%) acquired measles in HS. Of the 11 (79%) case-patients who accessed healthcare services while infectious, none were masked while waiting to see a provider and nine (82%) who had presented with rash and fever were not isolated promptly. In Hospital A, 421 (22%) of 1,872 HCP lacked evidence of measles immunity. Twenty-six (6%) of 404 HCP tested before vaccination were measles IgG seronegative including one who acquired measles.

Conclusions:
Failure to implement existing vaccine policy recommendations combined with delays in diagnosis and implementation of airborne precautions contributed to this outbreak, the largest U.S. nosocomial outbreak since 1988. Because patients with measles are likely to seek healthcare, healthcare providers should consider measles in patients with a rash illness and institute immediate airborne isolation. Ensuring HCP and the public are vaccinated in accordance with policy recommendations are paramount in preventing spread from imported measles.