January 1, 2020–March 28, 2024 are the dates for Measles in the United States

Precise News

Risk for widespread U.S. measles transmission remains low because of high population immunity.
** Results Reported Measles Cases and Outbreaks CDC was notified of 338 confirmed measles cases with rash onset during January 1, 2020–March 28, 2024 (Figure); cases occurred in 30 jurisdictions.
As of March 28, 2024, a total of 97 cases have been reported in 2024, representing 29% of all 338 measles cases reported during January 1, 2020–March 28, 2024, and more than a seventeenfold increase over the mean number of cases reported during the first quarter of 2020–2023 (five cases).
Imported Measles Cases Among all 338 cases, 326 (96%) were associated with an importation; 12 (4%) had an unknown source.
U.S. measles elimination reduces the number of cases, deaths, and costs that would occur if endemic measles transmission were reestablished.
As of March 28, 2024, a total of 97 confirmed measles cases have been reported in the United States in 2024, compared with a mean of five cases during the first quarter of each year during 2020–2023.
Second, case investigations resulting in discarded measles cases (i.e., a diagnosis of measles excluded) are not nationally reportable, which limits the ability to directly evaluate the sensitivity of measles case investigations.
Implications for Public Health Practice The U.S. measles elimination status will continue to be threatened by global increases in measles incidence and decreases in global, national, and local measles vaccination coverage.



In the United States, measles was declared eradicated in 2000. It is a highly contagious febrile rash illness. Importations of measles nevertheless persist, and U.S. S. Due to two protracted outbreaks among communities in New York and New York City that were not vaccinated, the measles elimination status was in jeopardy in 2019. To evaluate U.S. s. the measles elimination status following the 2019 outbreaks and to offer background information for comprehending the recent surges in measles cases, the CDC examined laboratory surveillance and epidemiologic data, as well as the effectiveness of the U.S. s. following these outbreaks, the measles surveillance program. The Centers for Disease Control and Prevention (CDC) was notified of 338 confirmed cases of measles between January 1, 2020, and March 28, 2024. Of these cases, 97 (or 29 percent) happened in the first quarter of 2024, which is more than seventeen times the mean number of cases reported in the same period both years. 336 case investigations contained data on ≥80% of critical surveillance indicators, 309 (91 percent) patients were unvaccinated or had an unknown vaccination status, and the median patient age among the 338 reported cases was 3 years (range = 0–64 years). The longest transmission chain throughout 2020–2023 lasted 63 days. By year’s end in 2023, with a robust surveillance system in place and no continuous measles virus transmission for a full year, U.S. S. The status of the measles was kept at elimination. Danger of widespread U.S. S. Due to strong population immunity, measles transmission is still rare. Nevertheless, given the spike in cases in the first quarter of 2024, more efforts are required to raise U. s. routine vaccination against the measles, mumps, and rubella, particularly in close-knit and undervaccinated communities. Among these initiatives are promoting vaccination prior to international travel and acting quickly to look into any suspected cases of measles.


Measles case reporting and classification.

State health departments notify the Centers for Disease Control and Prevention (CDC) of confirmed cases of measles via the National Notifiable Disease Surveillance System and by phone or email to the National Center for Immunization and Respiratory Diseases. The Council of State and Territorial Epidemiologists categorizes measles cases as either import-associated or internationally imported, depending on whether they were epidemiologically linked to an imported case or possessed viral genetic evidence of an imported measles genotype (1). Cases that lack any link to an imported case are classified as having an unknown source. Based on the standard guidelines for characterizing sequence variants provided by the World Health Organization (WHO)´ (3), unique sequences for this analysis were defined as those that differed by at least one nucleotide in the N-450 sequence (the 450 nucleotides encoding the carboxyl-terminal 150 nucleoprotein amino acids). The Advisory Committee on Immunization Practices recommendations (4) were followed in classifying unvaccinated patients as eligible for vaccination if they had not received any vaccinations. A surveillance system was considered to be functioning well if at least 80% of cases satisfied all three of the following criteria: the cases had to be classified as import-associated, the reports had to include full details on at least eight of the ten crucial surveillance indicators (i.e. E. location, gender, age, frequency of fever and rash, date of rash onset, immunization history, travel history, hospital stay, environment of transmission, and if the case was connected to an outbreak) (5), and laboratory-confirmed and verified.

Evaluation of the Transmission Chains.

Based on established epidemiologic connections, cases were categorized into three chains of transmission: isolated cases (single cases), two-case chains (two cases linked by epidemiology), and outbreaks (three or more linked by epidemiology). By calculating the time interval between each measles rash onset date in the chain, the possibility of missed cases within two-case chains and outbreaks was evaluated. Chains with more than one maximum incubation period (21 days) between cases may have a missing case. Following CDC policy and applicable federal law, this activity was reviewed by the organization and determined not to be research. *.


Records of Measles Cases and Epidemics.

The Centers for Disease Control and Prevention (CDC) was informed of 338 confirmed cases of measles that occurred in 30 jurisdictions between January 1, 2020, and March 28, 2024 (Figure). Twelve out of the thirteen cases in 2020 occurred before COVID-19 mitigating actions started in March of that same year. Out of the 170 cases that were reported in 2021 and 2022, 133 (78%) were linked to specific outbreaks: 49 cases in 2021—47 (96%) of which occurred among Afghan evacuees temporarily housed at U.S. s. military installations during Operation Allies Welcome, and an outbreak in central Ohio was linked to 86 (71%) of the 121 cases in 2022. Four outbreaks were linked to 28 (48 percent) of the 58 cases that occurred in 2023. As of March 28, 2024, 97 cases had been reported in 2024, accounting for 29% of the 338 cases of measles that were reported between January 1, 2020, and March 28, 2024. This is more than a seventeen-fold increase over the mean number of cases reported during the first quarter of 2020–2023, which was five cases.

traits of cases of measles that have been reported.

The age range of the patients was 0–64 years, with a median of 3 years. Of the 191 cases, or 58%, the patients were between the ages of 16 months and 19 years (Table). In total, 29 (9%) of the patients had previously received ≥1 MMR vaccination dose, while 309 (91%) were either unvaccinated (68%) or had an unknown vaccination status (23 percent). Of the 309 cases involving individuals who were either unvaccinated or whose vaccination status was unknown, 259 (84 percent) patients met the eligibility requirements for vaccination, 40 (13 percent) were between the ages of 6 and 11 months and were therefore not advised to receive a routine MMR vaccination, and 10 (3 percent) were too young to receive an MMR vaccination. Of the 155 hospitalized patients (46 percent) with measles, 109 (70 percent) were younger than 5 years old; 92 percent of these patients were either unvaccinated or had an unclear vaccination history. There were no recorded measles-related deaths to the CDC.

Cases of Measles Imported.

Of the 338 cases, 326 (96%) had an importation linked to them, while 12 (4%) had an unidentified source. 200 (61%) of the 326 cases connected to imports happened among U. S. residents who did not know their vaccination status or who were eligible for vaccination but chose not to receive one. 34 (37 percent) of the 93 (28 percent) measles cases that were directly imported from other nations happened in foreign visitors, and 59 (63 percent) occurred in U.S. S. inhabitants, 53 (90%) of whom were either unvaccinated or whose vaccination status was unknown despite being eligible for vaccination. In a U.S., one case (2 percent). s. occurred in one individual who was too young to receive the MMR vaccine, two (3%) in individuals who had already received one dose of the vaccine, and three (5%) in individuals who had already received two doses of the vaccine. WHO areas in Africa (24) and the Eastern Mediterranean (48) were the most frequent sources of cases that were imported from outside during the study period. Six cases of international importation from the European and South-East Asian WHO regions were reported during the first quarter of 2024. This is fifty percent more than the average number of importations from these regions between 2020 and 2023 (mean of two importations annually from each region).

Measures of Surveillance Quality.

All 338 case investigations had information on at least 80% of the critical surveillance indicators, with the exception of two, which had information on only 70% of the indicators. 219 (65%) case investigations had the date of the first case report to a health department available; 127 (58%) cases had the date of rash onset (IQR = 4 days before to 3 days after) at or before the time of case report. All told, 314 (93%) of the cases of measles were confirmed in the lab. Of those, 16 (5%) were confirmed by immunoglobulin M (serologic) testing alone, and 298 (95%) by real-time reverse transcription–polymerase chain reaction (rRT-PCR). Of the 298 rRT-PCR-positive specimens, 221 (74%) were successfully genotyped; of these, 177 (80%) had genotype B3 and 44 (20%) had genotype D8 and so on. (Supplementary Figure, https://stacks . cdc . gov/view/cdc/152776) Twenty-two distinct sequence identifiers (DSIds) (3) for genotype B3 and thirteen DSIds for genotype D8 were found. For any given DSId, the longest detection period was 15 weeks (DSId 8346).

Transmission Chains.

92 transmission chains were identified from the 338 measles cases (Table); 62 (67 percent) of these chains consisted of single cases, 10 (11 percent) of two-case chains, and 20 (22 percent) of outbreaks involving three or more cases. Of the 20 outbreaks, seven (or 35%) happened in 2024. §^ The median length of transmission was 20 days (range = 6–63 days), and the median outbreak size was six cases (range = three–86 cases). No two cases in any of the thirty two-case chains or outbreaks had more than one maximum incubation period (21 days) between them.


As of the end of 2023, measles elimination has remained in place in the United States due to the lack of endemic measles virus transmission for a continuous 12-month period in the presence of an efficient surveillance system. U. s. When measles is eradicated, endemic measles transmission is prevented, which lowers the number of cases, deaths, and expenses. Examination of nearly every U.S. s. Measles cases reported since January 2020 have been linked to imports, have full details on important surveillance variables, have been laboratory-confirmed by rRT-PCR, and have been genotyped. These results show that the U.S. s. The system for monitoring measles cases is working effectively. Isolated cases and a range of transmission chain sizes were found, indicating that persistent measles transmission would be quickly discovered. Nonetheless, a fresh threat to eradication is posed by the sharp rise in cases of measles reported in the first quarter of 2024.

The majority of measles importations were cases among travelers to and from nations in the WHO’s Eastern Mediterranean and African regions, which in 2021–2022 had the highest reported measles incidence (6). From November 2022 to October 2023, there were 49 countries, up 123 percent, reporting significant or disruptive outbreaks. According to global estimates, the percentage of children under one year old who received a first-dose measles vaccination dropped from 86 percent in 2019 to 83 percent in 2022, potentially harming nearly 22 million children (6).

As was the case in years prior to postelimination (7), the majority of imported cases of measles were among unvaccinated U. S. citizens. There is a greater chance of importations into the United States due to rising global measles incidence and falling vaccination coverage. S. neighborhoods, as seen in the first quarter of 2024, bolster the CDC’s advice that people get the MMR vaccine prior to traveling abroad (4).

To sustain measles elimination, high rates of MMR vaccination at the local and national levels must be maintained. Peril of extensive U.S. s. There is still a low rate of measles transmission due to high population immunity; however, the national 2-dose MMR vaccination coverage has not reached the Healthy People 2030 target of 95% (the estimated population-level immunity required to prevent sustained measles transmission) (8) for three years running, making about 250,000 kindergarteners susceptible to the disease annually (9). Additionally, 12-state coverage estimates for 2-dose MMR vaccinations were less than 90% in the District of Columbia and 12 states had exemption rates exceeding 5% among kindergarten students in 2022–2023 (9). As demonstrated by the 2022 outbreak in central Ohio, where 42% of hospitalized cases and 94% of unvaccinated cases were unvaccinated, clusters of unvaccinated individuals put communities at risk for significant outbreaks (10). Public health organizations may be able to identify undervaccinated communities for focused interventions to increase vaccination coverage while preparing for potential measles outbreaks by tracking MMR vaccination coverage at the county and zip code levels. In contrast to the average of five cases reported in the first quarter of each year between 2020 and 2023, there have been 97 confirmed cases of measles reported in the United States as of March 28, 2024. Like the cases recorded between 2020 and 2023, the majority of the cases recorded in 2024 involved individuals under the age of 20, who were either unvaccinated or whose vaccination status was uncertain, and were linked to an import. The prevention of measles and its complications, as well as the maintenance of high national measles vaccination coverage, including improving coverage in undervaccinated populations, depend on the timely detection of cases, the prompt implementation of control measures, and the maintenance of U.S. S. status of elimination.


There are a minimum of three restrictions that apply to the report’s findings. Initially, it is possible that importations were not fully reported, as 4% of cases that were reported during the study period had an unknown source. Furthermore, measles cases that were discarded as a result of case investigations (i.e. E. , a diagnosis of measles excluded) are not required to be reported nationally, which makes it more difficult to assess how sensitive measles case findings are. Nonetheless, surveillance is still sensitive enough to identify lone cases and outbreaks, and strong molecular epidemiology adds more proof that there hasn’t been a persistent measles outbreak in the US. Last but not least, for 35% of case investigations, the date of the initial case report to a health department was unavailable.

consequences for the practice of public health.

The USA. s. Global rises in measles incidence and declines in global, national, and local measles vaccination coverage will continue to jeopardize the status of the measles elimination. The United States has a high level of population immunity, so there is little chance of the disease spreading widely. Nevertheless, in order to keep the disease eradicated, steps must be taken to boost routine MMR vaccination coverage, promote vaccination prior to travel abroad, identify communities at risk for measles transmission, and quickly look into suspected cases.

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