Hantavirus global briefing — September 22, 2026: an urban rat reservoir in Salvador, and a second Andes Sur case in Neuquén

Global hantavirus activity reported between 19 and 22 September 2026 (display timezone UTC+08:00), the interval since the September 19 edition, left the alert layer where it was and moved the science. No agency issued a new hantavirus position in the window, and no national series this briefing follows week to week published a new issue. The window's one new peer-reviewed measurement was taken indoors, in a city.

Zeppelini and colleagues trapped 120 Norway rats across four low-income communities of Salvador, Brazil, and modelled what predicted hantavirus positivity in the 108 that were tested. Older animals and sites with accumulated materials were positively associated with hantavirus positivity; rodent-control campaigns and male sex came out as protective factors. 1 The reservoir work behind it in earlier editions came from rural settings: Argentine provincial trapping, a Kazakh steppe survey and European bank voles.

One human event belongs on the record with an earlier date than the window. Neuquén province in Argentina confirmed its second hantavirus case of 2026 on 2 September, in a person who fell ill under surveillance as a close contact of the province's fatal first case, and the provincial laboratory confirmed Andes Sur variant transmission between the two. 2

The only human numbers this edition can stand behind come from Germany and Argentina, and both series stand where the last edition left them. Germany's statutory table for week 37 reads 5 notifications in the week, 215 for the year to date and 217 over the same stretch of 2025. 3 Argentina's national bulletin has not moved past week 35, so its hantavirosis row holds at 58 events for 2026 against a 2022–2025 median of 41. 4

The human picture: four denominators, none renewed

Four figures currently stand for human hantavirus disease in the regions this briefing watches most closely. Each uses a different frame, and the dates matter as much as the numbers: three of the four were last refreshed in August.

Measure	Frame and cut-off	Figure
Germany, statutory notifications	Robert Koch Institute Epidemiologisches Bulletin 38/2026, reporting week 37, published 17 September 2026 3	5 in the week; 215 for weeks 1–37 of 2026; 217 for the same period of 2025
Argentina, national hantavirosis quick table	Boletín Epidemiológico Nacional 825, week 35 (30 August–5 September 2026) 5	58 events accumulated in 2026, against a 2022–2025 median of 41; above the expected range for the year, within it across the last four weeks
Chile, national hantavirus bulletin	Ministry of Health Boletín Epidemiológico de Hantavirus, week 31, reported 24 August 2026 6	49 confirmed cases and 19 deaths, case fatality 39%; 44 cases and 8 deaths across the whole of 2025
Americas region	PAHO, 2025 and 2026 to mid-April 7	229 confirmed cases and 59 deaths in 2025 across eight countries; 94 cases and 13 deaths in 2026 through mid-April

Germany's cumulative column absorbs late reports, so the five notifications recorded in week 37 sit alongside ten added to the year-to-date total since the previous bulletin. 3 The two-notification gap between 215 and 217 will therefore keep shifting.

Chile's bulletin remains the fullest national picture any Southern Cone country has published this year. Its 2026 case count already runs 11% above the whole of 2025, deaths stand at more than twice last year's eight, and the reported geographic range runs from the O'Higgins region south to Magallanes. 6 Of the 19 people who died, 68% were men and the median age was 37.

The Argentine row still carries no provincial breakdown, so the national figure supports no statement about where inside the country the 58 events fell. 5 Provincial detail arrives through other channels, and Neuquén's is the one that moved.

Neuquén: a second case, and transmission traced between two people

Neuquén's index case for 2026 was a 26-year-old man who lived in the rural centre of the province and worked on the land in the Pehuén district. He reached the Aluminé hospital with a fever above 38°C, muscle pain, breathing difficulty and severe abdominal pain, was transferred to intensive care in Zapala, needed mechanical ventilation, and died after 48 hours of hospital care. Hydatid cysts complicated his diagnosis. 2

Public health teams then traced the people who had shared a household, a journey or a care episode with him, and isolated 15 of them preventively while the investigation ran across Ruca Choroy, Aluminé and Zapala. One of those contacts developed early symptoms while under surveillance. The provincial laboratory confirmed hantavirus, and the province classified the infection as transmission between people. The patient was admitted in Zapala, and the remaining contacts stayed in strict home isolation with passive and active follow-up by the provincial epidemiology directorate. 2

Andes Sur circulates in Neuquén, Río Negro and Chubut. Among the recognised hantaviruses it is the one with documented transmission between people, generally through prolonged close contact. The province averages about two cases a year, with a peak of eight in 2001 and a stretch without notifications between 2014 and 2016. 2 The 2 September confirmation makes Neuquén's 2026 count two cases and one death.

The alert layer: no agency moved

WHO's newest hantavirus notice remains the 2 July posting that closed the cruise-ship event at 13 cases, three deaths and a case fatality ratio of 23%, with all contacts completing the 42-day follow-up. 8 The WHO emergency-event index for that outbreak lists five notices and no sixth, the most recent dated 2 July. 9

ECDC's communicable disease threats report for 12–18 September, published on 18 September, covers Ebola, malaria, botulism, avian influenza A(H9N2), influenza A(H5), respiratory virus epidemiology in the EU/EEA, West Nile virus, chikungunya, dengue, Crimean-Congo haemorrhagic fever, Vibrio, measles and expert deployments. Hantavirus and Andes virus sit outside that list, and the same report remains the newest issue the agency has published. 10 The week-39 issue is the next one due, on 25 September.

PAHO's epidemiological alert list carries nothing hantavirus-related newer than its December 2025 alert on hantavirus pulmonary syndrome; the newest entry on that list is a 26 August update on avian influenza A(H5). 11

The European Commission's outbreak page still carries no entry later than its 4 September flash report of the Health Security Committee working group, and its standing assessment holds: the risk to the general population in the EU/EEA from imported Andes virus is very low. 12

In Washington, the CDC's situation page remains an archive shell dated 7 July 2026, with national case reporting current through 2023. 13 The agency's last hantavirus-specific clinician notice is the 18 May health update on testing, which describes the cruise-linked cluster and reports no confirmed Andes virus cases in the United States. 14

The reservoir moves indoors: 108 rats in Salvador

One hundred and twenty Norway rats were trapped across four urban poor communities in Salvador, in Bahia state, Brazil. Of those, 109 were modelled for Leptospira and 108 for hantavirus. Environmental and demographic variables went into generalised linear models, and a stepwise procedure using Akaike's information criterion selected the terms that survived. 1

Model	Sample	Terms selected
Hantavirus positivity	108 rats	Age and presence of accumulated materials positively associated; rodent-control campaigns and male sex protective 1
Leptospira positivity	109 rats	Age, Calodium hepaticum scars, wounds, accumulated materials, open sewer canals and unpaved soil positively associated 1

Two things about this study matter for surveillance reading, and both are about what kind of result it is. The associations are model outputs from a single cross-sectional trapping round, so they describe which animals and which sites were more likely to test positive, and they establish nothing about what causes infection. The authors say as much in their own framing: different subsets of environmental and demographic factors shape pathogens with different epidemiology, so control programmes that work for one may miss the other. 1

The abstract reports no overall hantavirus prevalence for the 108 rats and no virus species identification for the animals that tested positive. Norway rats are the reservoir for Seoul virus, which causes a milder form of haemorrhagic fever with renal syndrome and circulates worldwide with its host. 15 The protective finding on rodent-control campaigns is the study's most directly actionable term, and it comes from an association observed in a single trapping round. 1

The study's setting is what separates it from the reservoir work this briefing has carried before. The West Kazakhstan survey posted on 18 September sampled rural districts and pooled lung tissue into testing units; 16 the Czech vole study counted co-infections in an overpopulated field population. The Salvador sample came from rats living alongside people in the same neighbourhoods, which is the exposure setting that Seoul virus surveillance is built around.

Research triage

Ecological drivers of hantavirus in an urban Norway rat population — EcoHealth, September 21

Authors and group: Carlos G. Zeppelini is first author, at the Institute of Collective Health of the Federal University of Bahia and the Swedish University of Agricultural Sciences in Umeå, with co-authors from the Federal University of Bahia, Fundação Oswaldo Cruz and Fiocruz Bahia, the London School of Hygiene and Tropical Medicine, Yale School of Public Health and the University of Liverpool.
Design: Cross-sectional trapping survey with generalised linear models and stepwise selection by Akaike's information criterion. One hundred and twenty Norway rats trapped in four urban poor communities, tested for Leptospira and hantavirus.
Dates: Published online 21 September 2026. DOI 10.1007/s10393-026-01836-z.
What it reports: Hantavirus positivity modelled on 108 rats, with age and accumulated materials positively associated and rodent-control campaigns and male sex protective. Leptospira positivity modelled on 109 rats, with a different set of terms selected, associating that pathogen with infestation markers such as open sewer canals and unpaved soil.
Limits: Single trapping round, so the design yields associations only. The abstract reports no overall hantavirus prevalence and no virus species identification for the positive animals, which leaves open which hantavirus was circulating.
Original: Differences in Ecological Drivers for Leptospira and Hantavirus in an Urban Norway Rat Population, EcoHealth

Hantaviruses at an inflection point — Frontiers in Virology, September 18

Authors and group: Ilyes Zatla, an independent researcher in Tlemcen, Algeria, as sole author. Published 18 September 2026 in the section Fundamental Virology.
Design: Narrative review. PubMed, Scopus, Web of Science, Google Scholar, and WHO, CDC and ECDC reports were searched through May 2026, with priority given to peer-reviewed articles, systematic reviews, surveillance reports and official outbreak communications. Studies without scientific validation and duplicate reports were excluded.
Dates: Published 18 September 2026. DOI 10.3389/fviro.2026.1883348.
What it reports: A synthesis of taxonomy, replication biology, transmission routes, reservoir ecology, pathogenesis, diagnostics and management, framed through a One Health programme of integrated human, animal and environmental surveillance, reservoir monitoring and intersectoral coordination. The review records rising hantavirus case numbers in Argentina across 2025–2026 and states that the drivers are still under investigation. Its reservoir table pairs each virus with its host — Hantaan with Apodemus agrarius, Seoul with Rattus norvegicus, Puumala with Myodes glareolus, Dobrava-Belgrade with Apodemus flavicollis, Sin Nombre with Peromyscus maniculatus, Andes with Oligoryzomys longicaudatus — and gives reported case-fatality ranges from under 1% for Seoul and Puumala to 35–50% for Andes.
Limits: A single-author narrative review with no protocol registration and no systematic quality appraisal, so its synthesis carries the author's selection. It reports no new case denominator, no field measurement and no experimental result. The search closed in May 2026, which places the September literature outside it.
Original: Hantaviruses at an inflection point: scientific evidence, spillover risk, and One Health approach, Frontiers in Virology

Watchpoints

Argentina's week-36 bulletin. The index page's newest issue is week 35. A new issue would show whether the 58-against-41 row holds or moves, and would carry the first provincial breakdown since week 35. 4
ECDC week 39, due 25 September. No hantavirus item has appeared in the weekly report through the 18 September issue. A first appearance on the active-threat list would be the clearest signal that European assessment had changed. 10
RKI Bulletin 39/2026, due 24 September. Germany's year-to-date column gained ten notifications in one week, so the 215-against-217 comparison will keep shifting as late reports land. 3
Neuquén's contact monitoring. The second case surfaced inside a monitored group, and the province has been following the remaining contacts in home isolation. A third case, or the closure of the monitoring period, settles whether the transmission chain stopped at two. 2
Typing the Salvador rats. Species identification on the stored Salvador samples would turn a pair of model associations into a named virus with a known clinical picture, and would fix which hantavirus circulates alongside people in that city. 1