PAHO warns of rise of yellow fever in the Americas

News brief

Yellow fever infections are on the rise in several Americas countries, with the virus expanding its reach outside the zone where cases are typically reported, the Pan American Health Organization (PAHO) said yesterday in an epidemiologic alert. PAHO is one of the regional offices of the World Health Organization (WHO).

aedes mosquitoes — *Damrongpan / iStock*

The increased cases began at the end of 2024 and continued into the first weeks of 2025, with 61 cases reported in 2024, 30 of them fatal. The number exceeds the total of both 2022 and 2023 for Bolivia, Brazil, Colombia, and Peru. In January, the region reported 17 more cases, 7 of them fatal.

PAHO said that, in 2024, cases were mainly reported from the Amazon region of Bolivia, Brazil, Colombia, Guyana, and Peru. The disease has now started spreading outside the zone, however, especially in Brazil's Sao Paulo state and Colombia's Tolima department. Peru has reported a death from yellow fever, and PAHO warned that other countries could be affected.

Most cases involved unvaccinated people

Officials said most of the 2024 cases occurred in people who weren't vaccinated, and they urged countries to strengthen their vaccination programs and to take steps to inform people who are traveling to high-risk areas.

With the change in transmission pattern, PAHO urged countries in areas near affected zones to step up surveillance to quickly detect suspected cases and isolate and treat affected patients.

Nearly 30% of cats, dogs owned by COVID patients had SARS-CoV-2 antibodies by 2021

News brief

Mary Van Beusekom, MS

Woman holding cat and dog — *adogslifephoto / iStock*

Nearly 30% of cats and dogs belonging to COVID-infected patients in central Texas tested positive for SARS-CoV-2 antibodies, signaling previous infection, from 2020 to 2021, according to a study published yesterday on the preprint server bioRxiv.

A team led by researchers from the Universidade Federal de Vicosa in Brazil and Texas A&M University sampled 579 pets from 281 households with at least one COVID-infected person from June 2020 to May 2021. The study has not yet been peer-reviewed.

"Among all the wild, domestic, and captive animals that can be infected, pets living in households with active human infections… are particularly at-risk because of their prolonged, close proximity and indoor relationships with humans," the authors wrote. "Therefore, it is critical to understand factors associated with higher risk of human-to-pet transmission to protect the health of companion animals."

Cats more vulnerable to infection

Nineteen of 396 dogs (4.8%) and 21 out of 157 cats (13.4%) tested positive for SARS-CoV-2 on reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In addition, 95 of 382 dogs (25%) and 52 of 146 cats (36%) had SARS-CoV-2 neutralizing antibodies. Twenty-six pets of 10 other species tested negative.

Characterizing animal infections using active SARS-CoV-2 surveillance in pets at risk of infection may aid in One Health pandemic prevention, response, and management.

In total, 164 pets (29%) tested positive for SARS-CoV-2 via molecular and/or serologic testing, and 110 (39%) of 281 households had one or more animals with acute or previous infections.

Relative to dogs, cats were more likely to be infected and had higher antibody levels. Viruses isolated from a subset of respiratory swabs revealed six different SARS-CoV-2 strains in dogs and cats, including the B.1.1 lineage in a cat 1 month before the first documented US human case.

Risk factors for human infection included sharing a bed and food and kissing. The frequency of clinical signs reported by owners of animals with acute infections were similar to those with uninfected pets, which the authors said suggests that not all reported signs were caused by COVID-19.

"Characterizing animal infections using active SARS-CoV-2 surveillance in pets at risk of infection may aid in One Health pandemic prevention, response, and management," the researchers concluded.

Case study: Mpox in nursing home worker resulted in no spread

News brief

Stephanie Soucheray, MA

Despite widespread exposure, residents in a Kentucky nursing home in 2023 did not contract mpox from an infected worker, suggesting that routine caregiving is not a robust risk factor for mpox transmission.

A study spotlighting the case was published last week in the American Journal of Infection Control. In 2023, a certified nursing assistant (CNA) worked three shifts while infectious with mpox, exposing as many as 56 residents to the virus.

"The ill CNA reported working in all areas of the facility, provided feeding, hygiene, and other care as needed, and was not restricted to specific patients or areas of the building," the authors wrote. "The CNA reported adherence to standard precautions, which in their role generally meant glove use, unless other personal protective equipment was required by resident isolation precautions."

Standard safety precautions worked

Officials from the Kentucky Department of Public Health notified residents of exposure and offered all residents Jynneos vaccine as post-exposure prophylaxis (PEP). Almost half of the residents (26) were vaccinated 10 and 15 days after exposure.

At 21 days after the last day of possible exposure, no residents had experienced fever or skin lesions consistent with mpox.

"At 21 days after the last day of possible exposure, no residents had experienced fever or skin lesions consistent with mpox, and temperature and skin checks were discontinued. The index patient, the CNA, fully recovered," the authors wrote.

Vaccination likely did not play a significant a role in limiting spread. Rather, close adherence to glove-wearing and other standard precautions likely protected residents, the authors said.

PEP with Jynneos has been shown to be most effective within 4 days of exposure.