Buenos Aires Confirms First Locally Acquired Mpox Clade Ib Case

Argentine health authorities recently announced the country's first locally acquired case of mpox clade Ib. This development in Buenos Aires raises concerns about the potential for community transmission of this variant in South America.

The emergence of locally acquired clade Ib in Argentina underscores the virus's ability to establish transmission chains through sexual networks involving international travelers.

Buenos Aires, a major South American tourism hub, welcomed about 1.5 million foreign visitors last year.

The case, announced in report #9 on March 16, 2026, involves a man living in Buenos Aires who has no recent international travel history but reported sexual contact with multiple partners, including travelers, before the onset of symptoms. The patient is currently receiving outpatient treatment and is recovering. Contact tracing has begun, and there are recommendations for 21 days of follow-up monitoring.

Argentina's Ministry of Health has characterized clade Ib as being more severe and contagious than previous strains. They are urging health authorities to strengthen surveillance, ensure proper isolation until lesions have scabbed over, and provide healthcare workers with appropriate personal protective equipment.

Mpox first gained global attention in May 2022, primarily due to clade IIb of the virus. That outbreak resulted in over 100,000 confirmed cases worldwide across 122 countries, mostly transmitted sexually among men who have sex with men. Clade Ib differs from the milder clade IIb in terms of transmissibility.

In Argentina alone, approximately 1,129 confirmed cases and two deaths were reported between 2022 and early 2023. As of 2026, eight countries in the Americas, including Argentina, have reported a total of 172 mpox cases, with no deaths recorded to date.

As of March 20, 2026, effective mpox vaccines (JYNNEOS) are generally available in most countries.