WASHINGTON, United States (CMC) – The Pan American Health Organization (PAHO) has reiterated the importance of strengthening vaccination and surveillance systems in light of the resurgence of pertussis across several countries in the region.

PAHO is also warning about the emergence and spread of antibiotic-resistant strains.

The UN body raised the matter during a recent meeting with the Latin American and Caribbean Network for Antimicrobial Resistance Surveillance (ReLAVRA+), where the latest findings and response strategies to this highly contagious disease were discussed.

“Vaccination, surveillance, and the responsible use of antibiotics are critical to preventing pertussis from becoming a serious public health threat again,” said Pilar Ramón-Pardo, head of PAHO’s Special Programme on Antimicrobial Resistance.

“We still have time to contain this issue, but we must act now: increase vaccination coverage, strengthen early detection, and enhance our outbreak response capacity,” she added.

PAHO said one of the main challenges is that standard treatment relies on macrolide antibiotics, such as azithromycin, clarithromycin, and erythromycin. However, genetic mutations in Bordetella pertussis, particularly in the 23S rRNA gene, are reducing the effectiveness of these drugs, complicating treatment for patients and prevention among close contacts.

During the COVID-19 pandemic, the widespread and inappropriate use of antibiotics like azithromycin may have contributed to the emergence of resistant strains.

Since 2024, cases have been detected thanks to strengthened surveillance and diagnostic systems, including molecular testing and standardised methods in reference laboratories. These advancements, supported by international partnerships, have been key to identifying and containing these cases.

PAHO said given the widespread use of these antibiotics and high international mobility, there is a risk of broader spread if health responses are not reinforced.

It said antimicrobial resistance (AMR) occurs when bacteria develop mechanisms to evade the effects of drugs, rendering them ineffective. In the case of pertussis, this can limit treatment options, hinder outbreak control, and increase the risk of severe complications, particularly in areas with low vaccination coverage.

Pertussis, also known as whooping cough, can be prevented with three doses of the DPT vaccine in children under one year of age, with boosters during childhood and adolescence. However, in infected individuals, especially infants, it can lead to severe illness, with risks of complications or even death.

PAHO said the disease has resurged in the Americas and while 4,139 cases were reported in 2023, the number soared to 43,751 in 2024. In the first seven months of 2025, nine countries reported over 18,595 cases and 128 deaths.

PAHO said the resurgence is linked to declining vaccination rates and underscores the need for strengthened, standardised surveillance.

During the pandemic, regional coverage for the first (DTP1) and third (DTP3) doses of the vaccine dropped to historic lows of 87 per cent and 81 per cent in 2021, respectively. By 2023, a partial recovery was observed (90 per cent and 88 per cent), but these rates remain below the 95 per cent recommended by PAHO, with significant disparities within countries.

In addition to childhood vaccination, PAHO recommends vaccinating pregnant women, especially during outbreaks, and healthcare workers in contact with newborns.

PAHO said strengthening national reference laboratories with reliable, standardised diagnostic methods is essential for timely detection of resistance and guiding health authorities’ responses.

It said collaborative initiatives like PAHO’s ReLAVRA+ network and PAHO’s Genomic Surveillance Regional Networks (PAHOGen), along with other strategic partnerships, have enabled standardised methodologies and expanded surveillance capacity in several countries in the region.

PAHO said given this scenario, it is urging countries to bolster their diagnostic capacity, enhance technical training for health personnel, maintain or increase vaccination coverage, and establish active, standardised surveillance systems to enable a rapid and effective response to antimicrobial resistance.