National Update on Measles Cases and Outbreaks - United States, January 1-October 1, 2019.

During January 1-October 1, 2019, a total of 1,249 measles cases and 22 measles outbreaks were reported in the United States. This represents the most U.S. cases reported in a single year since 1992 (1), and the second highest number of reported outbreaks annually since measles was declared eliminated* in the United States in 2000 (2). Measles is an acute febrile rash illness with an attack rate of approximately 90% in susceptible household contacts (3). Domestic outbreaks can occur when travelers contract measles outside the United States and subsequently transmit infection to unvaccinated persons they expose in the United States. Among the 1,249 measles cases reported in 2019, 1,163 (93%) were associated with the 22 outbreaks, 1,107 (89%) were in patients who were unvaccinated or had an unknown vaccination status, and 119 (10%) measles patients were hospitalized. Closely related outbreaks in New York City (NYC) and New York State (NYS; excluding NYC), with ongoing transmission for nearly 1 year in large and close-knit Orthodox Jewish communities, accounted for 934 (75%) cases during 2019 and threatened the elimination status of measles in the United States. Robust responses in NYC and NYS were effective in controlling transmission before the 1-year mark; however, continued vigilance for additional cases within these communities is essential to determine whether elimination has been sustained. Collaboration between public health authorities and undervaccinated communities is important for preventing outbreaks and limiting transmission. The combination of maintenance of high national vaccination coverage with measles, mumps, and rubella vaccine (MMR) and rapid implementation of measles control measures remains the cornerstone for preventing widespread measles transmission (4).

Increase in Measles Cases - United States, January 1-April 26, 2019.

As of April 26, 2019, CDC had reported 704 cases of measles in the United States since the beginning of 2019, representing the largest number of cases reported in the country in a single year since 1994, when 963 cases occurred, and since measles was declared eliminated* in 2000 (1,2). Measles is a highly contagious, acute viral illness characterized by fever and a maculopapular rash; complications include pneumonia, encephalitis, and death. Among the 704 cases, 503 (71%) were in unvaccinated persons and 689 (98%) occurred in U.S. residents. Overall, 66 (9%) patients were hospitalized. Thirteen outbreaks have been reported in 2019, accounting for 663 cases, 94% of all reported cases. Six of the 13 outbreaks were associated with underimmunized close-knit communities and accounted for 88% of all cases. High 2-dose measles vaccination coverage in the United States has been critical to limiting transmission (3). However, increased global measles activity poses a risk to U.S. elimination, particularly when unvaccinated travelers acquire measles abroad and return to communities with low vaccination rates (4). Health care providers should ensure persons are up to date with measles, mumps, rubella (MMR) vaccine, including before international travel, and rapidly report all suspected cases of measles to public health authorities.

International Importations of Measles Virus into the United States During the Postelimination Era, 2001-2016.

BACKGROUND: Although measles was declared eliminated from the United States in 2000, measles cases and outbreaks continue to occur, resulting from importations of the disease from countries where it remains endemic. METHODS: We describe the epidemiology of international importations of measles virus into the United States during the postelimination era. RESULTS: From 2001 to 2016, 553 imported measles cases were reported to the Centers for Disease Control and Prevention. A median of 28 importations occurred each year (range: 18-80). The median age of imported case-patients was 18 years (range: 3 months-75 years); 87% were unvaccinated or had an unknown vaccination status. US residents (as opposed to foreign visitors) accounted for 62% of imported measles cases. Overall, 62% of all imported case-patients reported travel to countries in the Western Pacific and European Regions of the World Health Organization during their exposure periods. The number of measles importations from specific countries was related to the incidence of measles in and the volume of travel to and from the source country. CONCLUSIONS: Our findings emphasize the importance of measles vaccination of US residents aged ≥6 months before international travel according to the Advisory Committee on Immunization Practices recommendations and supporting global measles elimination efforts.

Increase in Acute Flaccid Myelitis - United States, 2018.

In August 2018, CDC noted an increased number of reports of patients having symptoms clinically compatible with acute flaccid myelitis (AFM), a rare condition characterized by rapid onset of flaccid weakness in one or more limbs and spinal cord gray matter lesions, compared with August 2017. Since 2014, CDC has conducted surveillance for AFM using a standardized case definition (1,2). An Epi-X* notice was issued on August 23, 2018, to increase clinician awareness and provide guidance for case reporting.

Clinical evaluation and validation of laboratory methods for the diagnosis of Bordetella pertussis infection: Culture, polymerase chain reaction (PCR) and anti-pertussis toxin IgG serology (IgG-PT).

INTRODUCTION: The appropriate use of clinically accurate diagnostic tests is essential for the detection of pertussis, a poorly controlled vaccine-preventable disease. The purpose of this study was to estimate the sensitivity and specificity of different diagnostic criteria including culture, multi-target polymerase chain reaction (PCR), anti-pertussis toxin IgG (IgG-PT) serology, and the use of a clinical case definition. An additional objective was to describe the optimal timing of specimen collection for the various tests. METHODS: Clinical specimens were collected from patients with cough illness at seven locations across the United States between 2007 and 2011. Nasopharyngeal and blood specimens were collected from each patient during the enrollment visit. Patients who had been coughing for ≤ 2 weeks were asked to return in 2-4 weeks for collection of a second, convalescent blood specimen. Sensitivity and specificity of each diagnostic test were estimated using three methods-pertussis culture as the "gold standard," composite reference standard analysis (CRS), and latent class analysis (LCA). RESULTS: Overall, 868 patients were enrolled and 13.6% were B. pertussis positive by at least one diagnostic test. In a sample of 545 participants with non-missing data on all four diagnostic criteria, culture was 64.0% sensitive, PCR was 90.6% sensitive, and both were 100% specific by LCA. CRS and LCA methods increased the sensitivity estimates for convalescent serology and the clinical case definition over the culture-based estimates. Culture and PCR were most sensitive when performed during the first two weeks of cough; serology was optimally sensitive after the second week of cough. CONCLUSIONS: Timing of specimen collection in relation to onset of illness should be considered when ordering diagnostic tests for pertussis. Consideration should be given to including IgG-PT serology as a confirmatory test in the Council of State and Territorial Epidemiologists (CSTE) case definition for pertussis.

Evaluation of Level of Agreement in Bordetella Species Identification in Three U.S. Laboratories during a Period of Increased Pertussis.

While PCR is the most common method used for detecting Bordetella pertussis in the United States, most laboratories use insertion sequence 481 (IS481), which is not specific for B. pertussis; therefore, the relative contribution of other Bordetella species is not understood. The objectives of this study were to evaluate the proportion of other Bordetella species misidentified as B. pertussis during a period of increased pertussis incidence, determine the level of agreement in Bordetella species detection between U.S. commercial laboratories and the CDC, and assess the relative diagnostic sensitivity of CDC's PCR assay when using a different PCR master mix. Specimens collected between May 2012 and May 2013 were tested at two U.S. commercial laboratories for B. pertussis and B. parapertussis detection. Every fifth specimen positive for IS481 and/or IS1001 with cycle threshold (CT) values of ≤35 was sent to CDC for PCR testing that identifies Bordetella species. Specimens with indeterminate or negative results in the CDC PCR were tested using an alternate PCR master mix. Of 755 specimens, there was agreement in species identification for 83.4% (n = 630). Of the specimens with different identifications (n = 125), 79.2% (n = 99) were identified as indeterminate B. pertussis at CDC. Overall, 0.66% (n = 5) of the specimens were identified as B. holmesii or B. bronchiseptica at CDC. Of 115 specimens with indeterminate or negative results, 46.1% (n = 53) were B. pertussis positive when tested by an alternate master mix, suggesting a possible increase in assay sensitivity. This study demonstrates good agreement between the two U.S. commercial laboratories and CDC and little misidentification of Bordetella species during the 2012 U.S. epidemic.