Adria D Mathis1, Nakia S Clemmons1, Susan B Redd1, Huong Pham1, Jessica Leung1, Adam K Wharton1, Raydel Anderson1, Rebecca J McNall2, Elizabeth Rausch-Phung3, Jennifer B Rosen4, Debra Blog3, Jane R Zucker4,5, Bettina Bankamp1, Paul A Rota1, Manisha Patel1, Paul A Gastañaduy1. 1. Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. 2. Division of Laboratory Systems, Center for Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. 3. New York State Department of Health, Albany, New York, USA. 4. New York City Department of Health and Mental Hygiene, Long Island City, New York, USA. 5. Immunization Services Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Abstract
BACKGROUND: Measles elimination (interruption of endemic measles virus transmission) in the United States was declared in 2000; however, the number of cases and outbreaks have increased in recent years. We characterized the epidemiology of measles outbreaks and measles transmission patterns after elimination to identify potential gaps in the US measles control program. METHODS: We analyzed national measles notification data from 1 January 2001 to 31 December 2019. We defined measles infection clusters as single cases (isolated cases not linked to additional cases), 2-case clusters, or outbreaks with ≥3 linked cases. We calculated the effective reproduction number (R) to assess changes in transmissibility and reviewed molecular epidemiology data. RESULTS: During 2001-2019, a total of 3873 measles cases, including 747 international importations, were reported in the United States; 29% of importations were associated with outbreaks. Among 871 clusters, 69% were single cases and 72% had no spread. Larger and longer clusters were reported since 2013, including 7 outbreaks with >50 cases lasting >2 months, 5 of which occurred in known underimmunized, close-knit communities. No measles lineage circulated in a single transmission chain for >12 months. Higher estimates of R were noted in recent years, although R remained below the epidemic threshold of 1. CONCLUSIONS: Current epidemiology continues to support the interruption of endemic measles virus transmission in the United States. However, larger and longer outbreaks in recent postelimination years and emerging trends of increased transmission in underimmunized communities emphasize the need for targeted approaches to close existing immunity gaps and maintain measles elimination. Published by Oxford University Press for the Infectious Diseases Society of America 2021.
BACKGROUND: Measles elimination (interruption of endemic measles virus transmission) in the United States was declared in 2000; however, the number of cases and outbreaks have increased in recent years. We characterized the epidemiology of measles outbreaks and measles transmission patterns after elimination to identify potential gaps in the US measles control program. METHODS: We analyzed national measles notification data from 1 January 2001 to 31 December 2019. We defined measles infection clusters as single cases (isolated cases not linked to additional cases), 2-case clusters, or outbreaks with ≥3 linked cases. We calculated the effective reproduction number (R) to assess changes in transmissibility and reviewed molecular epidemiology data. RESULTS: During 2001-2019, a total of 3873 measles cases, including 747 international importations, were reported in the United States; 29% of importations were associated with outbreaks. Among 871 clusters, 69% were single cases and 72% had no spread. Larger and longer clusters were reported since 2013, including 7 outbreaks with >50 cases lasting >2 months, 5 of which occurred in known underimmunized, close-knit communities. No measles lineage circulated in a single transmission chain for >12 months. Higher estimates of R were noted in recent years, although R remained below the epidemic threshold of 1. CONCLUSIONS: Current epidemiology continues to support the interruption of endemic measles virus transmission in the United States. However, larger and longer outbreaks in recent postelimination years and emerging trends of increased transmission in underimmunized communities emphasize the need for targeted approaches to close existing immunity gaps and maintain measles elimination. Published by Oxford University Press for the Infectious Diseases Society of America 2021.
Authors: Nina B Masters; Adria D Mathis; Jessica Leung; Kelley Raines; Nakia S Clemmons; Kathryn Miele; S Arunmozhi Balajee; Tatiana M Lanzieri; Mona Marin; Deborah L Christensen; Kevin R Clarke; Miguel A Cruz; Kathleen Gallagher; Shannon Gearhart; Alida M Gertz; Onalee Grady-Erickson; Caroline A Habrun; Gimin Kim; Michael H Kinzer; Shanna Miko; M Steven Oberste; Julia K Petras; Emily G Pieracci; Ian W Pray; Hannah G Rosenblum; James M Ross; Erin E Rothney; Hannah E Segaloff; Leah V Shepersky; Kimberly A Skrobarcek; Anna M Stadelman; Kelsey M Sumner; Michelle A Waltenburg; Michelle Weinberg; Mary Claire Worrell; Noelle E Bessette; Lilian R Peake; Marshall P Vogt; Meredith Robinson; Ryan P Westergaard; Richard H Griesser; Joseph P Icenogle; Stephen N Crooke; Bettina Bankamp; Scott E Stanley; Paul A Friedrichs; Larry D Fletcher; Iván A Zapata; Herbert O Wolfe; Pritesh H Gandhi; Julia Y Charles; Clive M Brown; Martin S Cetron; Nicki Pesik; Nancy W Knight; Francisco Alvarado-Ramy; Michael Bell; Leisel E Talley; Lisa D Rotz; Paul A Rota; David E Sugerman; Paul A Gastañaduy Journal: MMWR Morb Mortal Wkly Rep Date: 2022-04-29 Impact factor: 35.301