The Morbidity and Mortality Weekly Report (MMWR) is a series of epidemiological science periodicals published by the United States Centers for Disease Control and Prevention (CDC). The MMWR series comprises 4 publications: the Weekly Report (MMWR Weekly), published weekly on Thursdays, and 3 titles presenting longer-form reports published on an ad hoc basis: MMWR Recommendations and Reports, MMWR Surveillance Summaries, and MMWR Supplements. MMWR was originally established as Weekly Health Index in 1930, changing its title to Weekly Mortality Index in 1941 and Morbidity and Mortality in 1952. It acquired its current name in 1976. It is the main vehicle for publishing public health information and recommendations that have been received by the CDC from state health departments. Material published in the report is in the public domain and may be reprinted without permission. , the journal’s acting editor-in-chief is Leonard Jack, who also serves as editor-in-chief of the CDC's peer-reviewed journal Preventing Chronic Disease.
Publication history
MMWR has its roots in the establishment of the Public Health Service (PHS). On January 3, 1896, the Public Health Service began publishing Public Health Reports. Morbidity and mortality statistics were published in Public Health Reports until January 20, 1950, when they were transferred to a new publication of the PHS National Office of Vital Statistics called the Weekly Morbidity Report. In 1952, NOVS changed the name of this publication to the Morbidity and Mortality Weekly Report, which continues through the current day (2026).
Notable articles
Several notable articles have been published in the report including:
- The spread of hepatitis A among attendees of jam band concert tours (September 2003)
- Several dozen deaths in teens participating in what is called the "choking game" (February 2008)
- A report about the elevated death rate among fishermen in the Pacific Northwest (April 2008)
- Improvements in public health after the implementation of municipal smoking bans (January 2009)
- The initial reports of a novel swine flu virus which led to the 2009 flu pandemic (April 24, 2009)
On the other hand, there have been articles that have been controversial, such as a report stating a low concerns for risks of elevated blood levels of lead in Washington, DC (April 2004). The article was notable and later criticized for not emphasizing the risks, and now is available together with two amending "notices to the readers" by CDC from 2010.
First report of AIDS
Five cases of Pneumocystis carinii pneumonia (PCP) were reported in what turned out to be the first reporting of AIDS in the medical literature (June 5, 1981). Los Angeles-based general practitioner Joel Weisman and immunologist Michael S. Gottlieb of the UCLA Medical Center had encountered a series of gay male patients with symptoms that appeared to be immune system disorders including significant loss of weight and swollen lymph nodes, accompanied by fever and rashes, in addition to two patients with chronic diarrhea, depressed white blood cell counts and fungal infections. Gottlieb diagnosed these and a number of his other patients as having pneumocystis pneumonia. A report they jointly wrote and published in the June 5, 1981, issue of Morbidity and Mortality Weekly Report, described their patients as "5 young men, all active homosexuals, [who] were treated for biopsy-confirmed Pneumocystis carinii pneumonia at 3 different hospitals in Los Angeles, California" of which "[t]wo of the patients died" by the time of the original report. This notice has been recognized as the first published report marking the official start of the AIDS pandemic and as "the first report on AIDS in the medical literature".
Drinking water lead report controversy
Background
Between 2001 and 2003, various tests showed that the lead content in drinking water in Washington DC more that 10% of the tests were higher than 15 ppb (parts per billion), which was the "action level" fixed by U.S. Environmental Protection Agency (EPA) for stagnant first draw water, and not indicative of typical usage. Some of the tests were prompted by EPA's lead and copper rule, while others were conducted by professor Marc Edwards, while trying to find the causes of an increased rate of pinhole leaks in copper water pipes. He found some rather high values in a few households, sometimes exceeding 1250 PPM. From 2002 on the matter started to be noted by news media.
Lead is well known to have toxic effects, especially for embryos and small children. Even in small doses, lead poisoning may lead to permanent intelligence deficiencies and concentration difficulties.
Report details
On March 30, 2004, an "MMWR dispatch", Blood Lead Levels in Residents of Homes with Elevated Lead in Tap Water – District of Columbia, 2004 was made available on the MMWR web site. It was then published by CDC as "MMWR Weekly, April 2, 2004 / 53(12); 268–270".
The results of Marc Edwards et al. came from analysis of the same raw data as those underlying the 2004 CDC report. In 2007, Edwards wrote to the CDC's associate director of science, James Stephens, questioning the report's conclusions and methodology, and the competence of its principal author. In 2008, Stephens answered him: "We have examined CDC's role in the study and have found no evidence of misconduct."
In 2009, the United States House of Representatives' Science and Technology Committee opened a congressional investigation into the 2004 CDC report. Starting in June 2020, Michael Caputo, the HHS assistant secretary for public affairs, and his chief advisor Paul Alexander tried to change, delay, suppress, and retroactively edit MMWR stories about the effectiveness of potential treatments for COVID-19, the transmissibility of the virus, and other issues where the president had taken a public stance. Caputo claimed this was necessary because MMWR reports were being tainted by "political content"; he demanded to know the political leanings of scientists who reported that hydroxychloroquine had little benefit as a treatment while Trump was saying the opposite. On September 14, 2020, the Select Subcommittee on the Coronavirus Crisis of the U.S. House of Representatives requested "transcribed interviews" with seven CDC and HHS personnel "to determine the scope of political interference with CDC's scientific reports and other efforts to combat the pandemic, the impact of this interference on CDC's mission, whether this interference is continuing, and the steps that Congress may need to take to stop it before more Americans die needlessly."
MMWR had its first-ever break in its 60-year history in 2025 when the January 23 and 30 releases were not published, due to the second Trump administration’s "pause" on public communications by all branches of HHS. The pause elicited widespread criticism, including from former MMWR editors. MMWR resumed publishing February 6 with two articles about potential health risks of recent Los Angeles area wildfires, coming days after Trump had criticized California governor Gavin Newsom over his handling of the January 2025 Southern California wildfires. Content scheduled in the skipped issues, including three studies about the then-ongoing avian flu outbreak, appeared in subsequent weeks.
In July 2025 MedPage Today reported that all scientific articles in the journal were required to obtain clearance from HHS Secretary Robert F. Kennedy Jr. prior to publication, although HHS disputed the claim.
MMWR stopped publishing October 1, 2025 at the start of the US federal government shutdown, and on October 10 MMWR staff were laid off. The firings were part of mass layoffs in 2025 ordered by Trump administration, which had stated its intent to lay off federal workers in "Democrat" programs, but were reversed the next day. MMWR resumed publication November 20, 2025, the week following funding and reopening of the US government. MMWR also missed its February 5, 2026 publishing date because of the January 31 - February 3 lapse in appropriations.
The Washington Post reported on April 9, 2026 that Jay Bhattacharya, acting directory of the CDC, had delayed a report that showed that the COVID-19 vaccine reduced the likelihood of hospitalizations and emergency room visits by half in the previous winter. The report had passed the CDC's scientific review process and was originally scheduled for release March 25, but Bhattacharya expressed doubts over its methodology. The Post reported on April 22 that the study had been fully rejected and that acting and former CDC officials believe it was rejected because it conflicted with the anti-vaccine views Robert F. Kennedy Jr. and that "MMWR is not currently a peer-reviewed journal, but we are working on changing that." The study was subequently published in manuscript form online.