The Pan American Health Organization (PAHO) urged countries in Central America, Mexico, and the Caribbean to strengthen their efforts to prevent dengue infections, given that those areas are entering their increased transmission season and that countries in South America have reported record activity this year.

In a May 24 epidemiologic alert, PAHO said the Americas region this year has already reported more than 8.1 million dengue cases, a 3.3-fold increase over the same period last year. More than 3,600 deaths have been reported among the cases. The hardest-hit countries include Brazil, Argentina, Paraguay, Peru, Colombia, and Mexico.

In Mexico and some Central America countries, dengue cases are already up between 2.5 and 6 times higher than the same time in 2023. In the Caribbean region, cases are up 5.7-fold from the previous year.

PAHO urged countries to focus on early diagnosis and proper management to prevent severe illness and death. It also urged public health officials to emphasize the importance of eliminating mosquito breeding sites and for people to avoid mosquito bites by wearing insect repellent and clothing to protect the arms and legs.

Immunity obtained through infections and post-exposure vaccination—not preventive vaccination—was likely the driving force of reduced mpox transmission in the Netherlands in 2022, according to new work from the Dutch National Institute for Public Health and the Environment (RIVM) published late last week in Eurosurveillance. The researchers also say behavior change also likely played a role.

The Netherlands reported its first mpox case on May 20, 2022, at the beginning of a global outbreak, and by December 31, 2023, a total of 1,294 cases had been documented.  As in other countries, 94% of cases were among men who have sex with men (MSM), and 99% of cases occurred in males. 

The primary preventive vaccination (PPV) program was launched on July 25, 2022, but the researchers showed that cases were already declining by early July among MSM.

Vaccine protection almost 70%

Overall, 29,851 PPV doses were administered from July 25, 2022 to April 30, 2023. The overall vaccine uptake rate was 45.8%, with 35.4% of the target population being fully vaccinated. The effectiveness of preventive vaccination was estimated at 68.2%.

The authors said the PPV program started at the peak of mpox transmission in the Netherlands.  

"By the time PPV would be effective, the incidence was already down to [about] five cases per day, making it unlikely that PPV contributed significantly to the decline of the outbreak," the authors said. 

The role of behavioural change could unfortunately not be adequately studied with the available data, but based on other studies it should not be ignored.

Infection-acquired immunity in a substantial proportion of those most at risk was the main factor in declining cases, with behavioral changes also likely playing a role, the authors concluded. "The role of behavioural change could unfortunately not be adequately studied with the available data, but based on other studies it should not be ignored," they noted.