The Weekly Epidemiological Record (WER) was first issued in 1926 by the Health Office of the League of Nations. It was entrusted to the World Health Organization (WHO) when it was created in 1948 and has appeared every week since then.
It serves as an essential instrument for the rapid and accurate dissemination of epidemiological information on cases and outbreaks of diseases under the IHR and on other communicable diseases of public health importance, including emerging or re-emerging infections.
An electronic version of the WER is accessible every Friday and can be downloaded free of charge.
Inside this issue
Highlighted signals and events
During epidemiological week 25 (15 June to 21 June 2026), WHO Public Health Intelligence (PHI) teams conducted digital event based surveillance (DEBS) to support the early detection and assessment of potential public health threats. During the reporting period, approximately 666 000 raw signals were scanned and triangulated through DEBS. From this large pool of signals, 36 signals and/or events met assessment thresholds and underwent further analysis and categorization. Of the 36 categorized signals, 33 represented unique signals, with the remaining entries reflecting updates or parallel reports of the same signals. Of these, 23 signals and/or events were escalated for operational attention.
In the reporting week, four new events were verified through PHI activities. In addition, one Disease Outbreak News (DON) was published, along with one Rapid Risk Assessment (RRA). A summary of identified raw signals, assessed signals, and published outputs is presented in the tables below.
| Screened signals1 | Signals categorized2 | Unique signals3 | Signals escalated4 |
| 666 000 | 36 | 33 | 23 |
1 Signals screened: Total volume of raw signals reviewed from across multiple sources during the reporting period.
2 Signals categorized: Number of signals categorized for further detailed WHO assessment and actions during the reporting period.
3 Unique signals: Count of distinct signals after removing duplicate or repeated entries from different sources within the same epidemiological week.
4 Signals escalated: Subset of categorized signals that triggered escalation actions.
| Region | Hazard |
| Africa | • Measles • Bacterial meningitis • Yellow fever • Cholera • Not yet diagnosed disease |
| Americas | • Missing radioactive source • Yellow fever • Diphtheria • Dengue • Contaminated infant formula (botulism) |
| Eastern Mediterranean | • Measles |
| Europe | • Salmonellosis |
| South-East Asia | • Malaria • Avian influenza A(H5N1) (zoo) |
| Western Pacific | • Mass mortality of seals due to A(H5N1) • Influenza A(H9) • Earthquake • Dengue |
5 The absence of listed signals indicates that no publicly available signals were identified during the reporting period and does not imply absence of signal activity overall.
| Disease Outbreak News (1) | |
| • | Ebola disease caused by Bundibugyo virus, Democratic Republic of the Congo & Uganda |
| Rapid Risk Assessment (1) | |
| • | WHO Rapid Risk Assessment - Yellow fever, Global v.1 |
Ebola disease caused by Bundibugyo virus, Democratic Republic of the Congo and Uganda
The Bundibugyo virus disease (BVD) outbreak in the Democratic Republic of the Congo continues to evolve rapidly, with increasing case numbers and geographic spread. As of 22 June, a cumulative of 1094 confirmed cases, including 277 deaths, have been reported from the Democratic Republic of the Congo. Uganda has reported 20 confirmed cases including two deaths, as well as one probable case who has died. To date, 115 patients in the Democratic Republic of the Congo and 15 patients in Uganda have been reported to have recovered. In Uganda, the outbreak remains epidemiologically linked to transmission originating in the Democratic Republic of the Congo, with evidence of both imported infections and secondary transmission among contacts and healthcare workers, but without any documented community transmission.
The outbreak in the Democratic Republic of the Congo is spread across 34 health zones in three provinces: Ituri, North Kivu and South Kivu. The outbreak remains concentrated in Ituri province, which accounts for over 90% of reported confirmed cases. The highest number of confirmed cases in Ituri province are reported from Bunia (296 cases), Mongbwalu (237 cases), Rwampara (225 cases), and Nyankunde (86 cases) health zones. Laboratory confirmation continues to be a constraint, and case detection is still severely constrained by insufficient human resources, limited logistics, and insecurity; thus, the full extent of the outbreak remains unknown. New health zones continue to be reported, although some of the newly reporting health zones’ cases had a date of onset as early as early May. Due to challenges in linking epidemiological and laboratory testing data, 17 confirmed positive cases remain to be allocated to health zones, further underscoring the incomplete understanding of the extent of the outbreak. Many cases remain unlinked epidemiologically, and many infectious cases are still in the community, as bed capacity and community acceptance of treatment centres and of safe and dignified burial remain challenging. Thus, the degree of community transmission remains very high.
Daily updates to case counts can be found here: Alert and Response.
Hantavirus outbreak linked to cruise ship travel, Multiple locations
The Andes hantavirus outbreak linked to cruise ship travel aboard the M/V Hondius remains limited to cases reported amongst passengers or crew members, with no evidence of transmission since the complete disembarkation and disinfection of the ship. The case count stands at a total of 13 cases, of which 12 are confirmed and one is probable; including three deaths (two confirmed and one probable).
Amongst the 10 living cases under treatment for hantavirus pulmonary syndrome, eight are reported to have recovered and been discharged, while two remain hospitalized.
The main epidemiological activity at this stage of the outbreak remains the contact tracing of the final disembarked contacts from the ship, as the contacts from earlier exposures (e.g., plane travel from Saint Helena and South Africa, United Kingdom Overseas Territories and South Africa; and disembarkation in Tenerife, Spain) have ended their 42-day follow-up period. There are thus around 50 contacts remaining, and the last contacts will complete their 42-day follow-up period on 1 July 2026, after which, assuming no further contacts become cases, the outbreak will be considered over.
Additional ongoing epidemiological activities include continued efforts to identify the source of the initial zoonotic spillover in South America, as efforts to date to overlay the travel route of the index case with the known distribution of Andes hantavirus have been unfruitful; and a cohort study of shipboard contacts to identify specific risk factors for infection.
For additional information on the evolution of the outbreak, please see the WHO Disease Outbreak News
Featured Content
100 Years of the Weekly Epidemiological Record
By the Editors of the Weekly Epidemiological Record
The Weekly Epidemiological Record premiered in April 1926 as a publication of the Health Office of the League of Nations, with simple telegraphed reports of case numbers and locations of the then five notifiable diseases – cholera, plague, smallpox, yellow fever and typhus. In April 2016, the WER marked its 90th anniversary (see WER Volume 91 Issue 13 pp 169-176 for a thorough treatment of the first 90 years). At that time, the global public health landscape already stood at a moment of uneasy transition: the West African Ebola epidemic had recently drawn to a close, Zika virus had revealed the complex links between infection, pregnancy and long-term disability, and antimicrobial resistance was steadily rising from a technical concern to a defining global threat. Few at the time could have anticipated how fully the next decade would test the foundations of epidemiological surveillance, international cooperation and public trust.
The past 10 years
Over the past decade, the WER has continued its quiet but unwavering presence, appearing weekly and documenting the shifting landscape of global health risks. As it has done since 1926, the WER has faithfully chronicled both progress and peril.
Between 2016 and 2019, the WER reflected a world grappling with a growing diversity of public health challenges. Long-standing communicable diseases remained stubbornly entrenched in many settings, while new and re-emerging threats demanded constant vigilance. Reports on measles resurgences, yellow fever and cholera outbreaks, and the continuing effort to eliminate poliomyelitis appeared alongside increasingly detailed analyses of vaccination policy and programme performance. During these years, the WER also regularly reported on certification milestones: countries achieving malaria-free status, progress towards the elimination of neglected tropical diseases, and strengthening surveillance systems under the International Health Regulations (IHR).
At the same time, the WER increasingly documented risks extending beyond classical infectious disease outbreaks. Climate-sensitive health threats, including changes in the geographic range of vector-borne diseases, appeared with growing frequency. Articles examining vaccine safety, influenza strain selection, and antimicrobial resistance underscored the expanding technical complexity of public health decision-making in an interconnected world.
COVID-19: a defining moment
Then, in early 2020, a novel coronavirus emerged and rapidly escaped containment. Within weeks, COVID-19 had transformed from a cluster of unexplained pneumonia cases into the defining global health crisis of a generation. Although the WER was no longer the primary vehicle for real-time outbreak notification – this role had shifted to WHO’s Disease Outbreak News and the Event Information Site under the IHR – the WER assumed a new importance as a stable platform for authoritative policy guidance and technical synthesis.
Throughout the pandemic years, the WER published critical outputs on vaccine evaluation and use, safety surveillance, and the recommendations of the Strategic Advisory Group of Experts (SAGE) on Immunization. As vaccines were developed at unprecedented speed, the WER became a global reference point for evidence-based guidance on product characteristics, target populations and evolving booster strategies, helping Member States navigate both scientific uncertainty and intense public scrutiny.
Beyond COVID-19: a crowded risk landscape
The COVID-19 era also made one reality unmistakable: pandemics do not pause other health threats. While COVID-19 dominated headlines, outbreaks of Ebola, Marburg virus disease, dengue, measles and the emerging global threat of mpox took their toll. Often through the lens of its long-standing tradition of publishing vaccine position papers, updates on progress towards disease elimination, and summaries of Disease Outbreak News, the WER persistently highlighted these concurrent risks, reminding readers that preparedness must be broad, sustained and adaptable.
Influenza – long familiar, yet perpetually unpredictable – continued to demand annual global coordination, with the WER publishing recommendations on vaccine composition that directly informed manufacturing and immunization policies worldwide.
Information as an intervention
Looking back from 2026, the past decade underscores a lesson as old as the WER itself: information is not ancillary to epidemic control—it is instrumental. Timely, reliable and widely accessible epidemiological intelligence shapes decisions that save lives. In an era of instantaneous communication and widespread misinformation, the value of a trusted, methodical and transparent record has only grown.
As the world faces an uncertain future marked by climate change, demographic shifts, technological transformation and persistent inequity, the need for such an anchor is clear. The last ten years have shown that health threats emerge faster, spread wider and reverberate more deeply than ever before. They have also shown that cooperation, grounded in shared evidence, remains humanity’s most reliable defense. Sadly, the past year has brought radical upheaval to the world of global public health, with massively shrinking budgets for overseas development assistance, increased skepticism of multilateralism, and increasing political instability.
New WER format
Against this backdrop, the WER has adapted too. With this issue we embark on a more modern format for the WER which refocuses on the WER’s roots as a timely method for disseminating epidemiological information about emerging health threats: coverage of WHO’s 24/7 public health intelligence activities to detect signals of potential public health events, and real-time updates about ongoing outbreaks of global concern, and for existing situation reports and other products to be consolidated in one place. Meanwhile, we retain the critical in-depth chronicling of major vaccine policy decisions, progress towards disease elimination, and other recurrent content for which the WER has come to be known. And as the format and scope adapts, we honor the legacy of all of those who have contributed to the WER over the last 100 years.
As it has done for a full century now, the Weekly Epidemiological Record continues to appear – documenting the unfolding history of global public health, one week at a time. While its format has evolved – from telegraphed bulletins to digital publication – the essence of the WER remains unchanged.