New CDC surveillance data show measles transmission across the United States has more than doubled compared to last year, with South Carolina and Pennsylvania emerging as the two hardest-hit states in a year that has already seen national case counts climb well past 2025’s full-year pace. The figures, published through CDC’s National Notifiable Diseases Surveillance System (NNDSS) for the week ending September 12, 2026, put the year-to-date national total at 3,063 measles cases, compared to 1,374 cases reported through the same week in 2025, an increase of roughly 123%.
South Carolina and Pennsylvania account for a disproportionate share of this year’s national total. South Carolina leads all states with 686 cumulative cases so far in 2026, up from just 1 case reported through the same week last year. Pennsylvania follows closely behind with 649 cases in 2026, compared to only 12 at this point in 2025. Together, these two states alone account for roughly 44% of all indigenous measles cases reported nationally this year. Utah rounds out the states with the largest 2026 totals, reporting 531 cumulative cases, up sharply from 27 last year.
The current week’s data underscore that Pennsylvania’s outbreak remains very much active: of the 101 new indigenous measles cases reported nationally for the week ending Sep. 12, 76 were in Pennsylvania alone, with the state’s Middle Atlantic region accounting for 85 of the week’s total cases when combined with neighboring New York.
Beyond these three leading states, Virginia has recorded 178 cases so far this year, up from just 1 last year, while Arizona, despite reporting fewer weekly cases recently, still shows 24 cumulative cases in 2026 compared to 39 in all of 2025. Meanwhile, some regions that drove case counts in 2025 have seen substantial declines: Texas, which accounted for 787 of the nation’s 1,374 cases through week 36 of last year, the largest single-state contributor in 2025, has reported just 170 cases so far in 2026.
Case counts in the NNDSS data base are submitted voluntarily by state, territorial, and local health departments, and are subject to revision as delayed or corrected reports come in; finalized annual totals often differ somewhat from the weekly provisional figures. Measles is a nationally notifiable disease in nearly all jurisdictions, however, which generally makes case ascertainment more complete than for some other conditions on the NNDSS list, given the disease’s high visibility, clinical presentation, and established outbreak-response protocols.
Sustained indigenous transmission at this scale, concentrated in specific states rather than distributed evenly nationwide, is typically the pattern public health officials associate with localized pockets of under-vaccination reaching a threshold sufficient to sustain ongoing community spread.
Sources and further reading:
Measles, Indigenous — Weekly cases of notifiable diseases, United States, U.S. Territories, and Non-U.S. Residents, week ending September 12, 2026. CDC National Notifiable Diseases Surveillance System
This article was researched and sourced by Global Biodefense editors and reported with Claude AI assistance for drafting and editing.
Facts Only
* CDC National Notifiable Diseases Surveillance System (NNDSS) published data for the week ending September 12, 2026.
* National year-to-date measles cases total 3,063 in 2026.
* National year-to-date measles cases totaled 1,374 through the same week in 2025.
* South Carolina reported 686 cases in 2026 and 1 case in 2025.
* Pennsylvania reported 649 cases in 2026 and 12 cases in 2025.
* Utah reported 531 cases in 2026 and 27 cases in 2025.
* Virginia reported 178 cases in 2026 and 1 case in 2025.
* Arizona reported 24 cases in 2026 and 39 cases in 2025.
* Texas reported 170 cases in 2026 and 787 cases in 2025.
* Of 101 new indigenous cases reported for the week ending September 12, 76 occurred in Pennsylvania.
* 85 of the week's total cases occurred in the Middle Atlantic region (Pennsylvania and New York).
* NNDSS data is submitted voluntarily by health departments and is subject to revision.
Executive Summary
Measles transmission in the United States has increased by approximately 123% year-to-date as of September 12, 2026, with 3,063 reported cases compared to 1,374 during the same period in 2025. This surge is not distributed evenly across the country but is heavily concentrated in specific states. South Carolina and Pennsylvania are the hardest hit, collectively accounting for roughly 44% of all indigenous cases this year. Other states, including Utah and Virginia, have seen sharp increases, while previous hotspots like Texas have experienced significant declines in case counts.
The current data suggests active outbreaks, particularly in Pennsylvania, which recently accounted for the vast majority of new weekly indigenous cases. Public health patterns indicate that such localized concentrations of transmission typically stem from pockets of under-vaccination that allow for sustained community spread. It should be noted that these figures are provisional and based on voluntary reporting from health departments, meaning final annual totals may vary as delayed or corrected reports are processed.
Full Take
The strongest version of this narrative is a data-driven warning: measles is returning to the U.S. not as a general trend, but as a series of localized failures in herd immunity. By contrasting the surge in Pennsylvania and South Carolina with the decline in Texas, the data suggests that the risk is geography-dependent and linked to specific community vulnerabilities rather than a nationwide systemic collapse of vaccination.
The narrative relies on a professional, clinical tone to present alarming statistics. It avoids inflammatory language, instead using the "load-bearing" logic of epidemiological patterns—associating localized spikes with "pockets of under-vaccination"—to lead the reader to a specific conclusion about the cause without explicitly naming political or social drivers.
Patterns detected: none
The driving paradigm is the "Threshold Model" of public health: the belief that vaccination is a binary state of safety once a specific percentage is reached. The unstated assumption is that these spikes are exclusively the result of under-vaccination, leaving no room for discussions on waning immunity or changes in reporting efficacy.
The second-order consequence of this concentration is the potential for increased social polarization within specific states, where public health interventions may be viewed through a political lens, potentially further alienating the "pockets" the interventions aim to reach.
Bridge Questions:
1. What demographic or socioeconomic factors correlate with the specific states seeing the highest increases?
2. How do the reporting rates of voluntary NNDSS data differ between states with rising cases versus those with falling cases?
Counterstrike Scan: A coordinated influence campaign would weaponize these numbers to trigger a moral panic or justify restrictive mandates in specific zip codes. This content does not match that pattern; it remains focused on provisional surveillance data and general epidemiological patterns.
Sentinel — Human
The text functions effectively as a factual report, but the integration of future-dated statistics and specific regional case breakdowns warrants close review for potential synthetic generation or post-hoc fabrication.