One in three suspected Havana fevers tested positive for Oropouche in 2024

Oropouche fever, an arboviral illness spread by Culicoides paraensis biting midges, established itself across Cuba during 2024, and a newly published investigation shows how deeply it penetrated the capital even as dengue testing kept obscuring it. Writing in the US Centers for Disease Control and Prevention journal Emerging Infectious Diseases, researchers at the Pedro Kourí Tropical Medicine Institute report that of 549 suspected cases logged in Havana between 1 June and 7 September 2024, 189 — 34.4% — were confirmed as Oropouche virus infection by real-time PCR [s1].

That share matters because Havana is a stress test for surveillance. The province holds roughly 2.12 million people, about a fifth of Cuba's population, and serves as the country's densest urban core and principal travel hub [s1]. An outbreak that takes hold there can seed the rest of the island quickly, and in 2024 it did.

From two provinces to the whole country

Cuba's Ministry of Public Health reported an Oropouche outbreak on 27 May 2024, first detected in Santiago de Cuba and Cienfuegos provinces, where acute febrile illness exceeded seasonal levels and dengue testing kept coming back negative [s1]. The national surveillance system flagged a possible emerging pathogen, and the National Reference Laboratory confirmed Oropouche virus circulation by PCR [s1]. Within three months the outbreak had spread nationwide, reaching 109 municipalities across all 15 provinces [s1]. By the end of 2024, the febrile surveillance system had identified 24,259 suspected cases, of which 626 were confirmed as Oropouche fever [s1].

The Havana slice of that picture is the investigators' focus. Incidence in the province reached 8.9 per 100,000 population, rising to 10.2 per 100,000 among adults aged 27 to 59 years [s1]. No cases were severe, and three infants tested positive [s1] — a detail the authors flag because Oropouche has drawn scrutiny elsewhere in the Americas over possible vertical transmission and effects in pregnancy.

Dengue kept the virus hidden

The central obstacle was not the pathogen but the diagnostic reflex built around a different one. Cuba experiences frequent dengue outbreaks that peak during May to November, exactly when the Oropouche signal emerged [s1]. Dengue IgM screening runs across 30 regional laboratories, while confirmatory PCR for Oropouche is centralised at the Havana institute, so a febrile patient who screened negative for dengue could still spend time in a system oriented toward the wrong virus [s1]. The case definition the investigators used reflected that reality: fever above 38°C with headache and at least one further symptom — myalgia, arthralgia, chills, low back pain or photophobia — plus a negative dengue IgM result and a link to an area of confirmed transmission within the previous two weeks [s1]. In practice, a patient entered the Oropouche count only after dengue had been ruled out first, so the virus was being measured through the gaps in another disease's surveillance net rather than on its own terms.

Testing capacity was itself a constraint. After Oropouche circulation was confirmed, the laboratory could not screen every suspected case universally and moved to testing a subset because of reagent shortages and operational limits [s1]. That means the confirmed count understates true infections, and the 34.4% positivity should be read as the yield of a strained system rather than a precise attack rate.

Why a Caribbean foothold is worth watching

Oropouche virus activity rose sharply across the Americas in 2024, surfacing in countries with no previously documented local transmission [s1]. Cuba's experience illustrates the practical problem that expansion creates: in settings where dengue, chikungunya, Zika and now Oropouche cocirculate, a surveillance system tuned to one arbovirus can let another move through a population before it is named. The Havana reference laboratory already monitors several of these viruses together, which is how the new signal was caught at all [s1].

The investigation does not describe an unusually dangerous illness — the Havana cases were mild and none were severe [s1]. Its value is as a map of how fast a new arbovirus can saturate a dense, well-connected capital, and of the diagnostic blind spots that let it. For countries across the region reorganising laboratory networks around multiplex arboviral testing, the lesson is that negative dengue results are not an all-clear, and that the window between first detection and nationwide spread can be measured in weeks rather than seasons. The three positive infants, flagged without elaboration in the report, are the kind of signal that only a system actively looking for Oropouche would record at all [s1] — and the main argument for keeping it in the testing panel as the virus settles into the Caribbean.