Respiratory virus detectives: Guardians of health in Argentina

Across a vast network spanning the Americas, sentinel surveillance sites generate critical data to track the circulation of respiratory viruses, assess their severity, identify the most vulnerable populations, and evaluate how well vaccines and other preventive measures perform under real-world conditions.

— February 2026 —

At the San Luis Pediatric Hospital, Belén gently strokes her belly as she waits to receive the respiratory syncytial virus (RSV) vaccine. The vaccine will protect her baby from severe infections such as bronchiolitis, one of the leading causes of pediatric hospitalization. Unbeknownst to her, this expectant mother is just steps away from a sentinel unit, which is a clinical, epidemiological, and laboratory teams that is working to help demonstrate that the vaccine significantly reduces hospitalizations in infants.

Currently, Argentina has 41 sentinel surveillance sites distributed across the country. Each center produces essential information on severe acute respiratory infections, which primarily affect children under five years of age and adults over 65.

“These units, which are part of the Argentine Sentinel Surveillance Network for Severe Acute Respiratory Infections, allow us to better understand the evolution of these diseases and their real impact on the population,” explained Eva Jané Llopis, Argentina Country Representative of the Pan American Health Organization (PAHO).

“Argentina was one of the pioneers in implementing the RSV vaccine, and thanks to the work of these units, it was possible to evaluate the effectiveness of the vaccine,” she added.

Studies showed a 62% effectiveness in reducing respiratory hospitalizations among infants under six months of age, as well as more than a 70% reduction in intensive care admissions.

The work of sentinel respiratory virus units begins in the clinical area with sample collection in intensive care.

National efforts and a broader network

Across the Americas, nearly 6,000 sentinel surveillance sites feed into two major networks coordinated by PAHO: SARInet plus, for the epidemiological surveillance of severe respiratory infections, and REVELAC-i, to measure the effectiveness of influenza and other respiratory virus vaccines.

Through these networks, countries share data and laboratory samples that make it possible to monitor the circulation of pathogens such as influenza virus, RSV, and SARS-CoV-2; measure the incidence of severe acute respiratory infections; identify the most affected populations; and evaluate whether vaccines and other interventions are working as expected.

This information guides decision-making: from defining the annual composition of the influenza vaccine to reorganizing health services when cases increase, as well as planning bed and resource availability, procuring medicines, or adjusting vaccination strategies. Each sentinel surveillance unit is an essential link in these regional and global collaboration networks.

In the province of San Luis, located in central-western Argentina, two units operate: one at the San Luis Pediatric Hospital, and another at the Dr. Ramón Carrillo Central Hospital.

“Both are highly complex facilities that receive referrals of pediatric and adult patients from across the province,” said Edgar Ribba, Director of Epidemiology for San Luis. Each unit is organized into three components: clinical, epidemiological, and laboratory.

The sample is labeled and sent to the laboratory under strict biosafety measures to be refrigerated until analysis.

What is a typical day like in a sentinel unit?

At the San Luis Pediatric Hospital, everything begins at Inpatient and Intensive Care Services. Silence dominates the environment, and it is a “quiet” day—although staff avoid using that word, since the situation can change within minutes.

When a patient meets the criteria for severe acute respiratory infection, the health team completes a detailed form, including personal information, medical history, vaccination status, symptom onset, and treatment received.

This form accompanies the sample collected via nasopharyngeal swab, which is stored in a special refrigerated container and sent to the laboratory under strict biosafety measures.

“The information collected by sentinel units about etiological agents is very important for designing epidemiological action plans to follow in inpatient wards and intensive care units, in isolation areas, and in patient cohorting,” described Gabriela Pérez, Head of Pediatrics at the hospital.

In the laboratory of this sentinel unit, samples are divided into two parts: one is processed locally, and the other is sent to the Provincial Public Health Laboratory, strategically located across from the hospital. There, samples are identified to ensure traceability, and genetic material is extracted to perform molecular RT-PCR (real-time polymerase chain reaction) tests to detect influenza, SARS-CoV-2, and RSV.

At the Public Health Laboratory of the Province of San Luis, various tests are performed to detect influenza, SARS-CoV-2, and respiratory syncytial virus.

Positive samples are then referred to the National Institute of Infectious Diseases (INEI) “Dr. Carlos Malbrán” for more advanced complementary studies of genomic characterization and subsequent submission to regional and global collaborating centers.

In parallel, the epidemiological component reviews the form and, using an algorithm, confirms whether the case meets the sentinel definition of severe acute respiratory infection. If so, and after completing the form with information from the digital medical record and consulting the medical team, the data are entered into the National Health Surveillance System (SNVS 2.0).

“We also verify vaccination history, both in pediatric patients and in the mothers of infants under six months of age, which is a key piece of information for effectiveness studies,” added Angélica Ramón from the Epidemiology Department of the San Luis Pediatric Hospital. With this information, they compare how many vaccinated and unvaccinated children become severely ill and thus determine, in real life, how well the vaccine is working.

In Argentina, sentinel units are part of the Ministry of Health’s “mosaic” surveillance strategy. Their contributions not only strengthen the local response but also support regional and global studies on the burden of these diseases and the effectiveness and impact of vaccination.

“Being part of the sentinel unit is a source of pride and a great responsibility because important data for protecting the health of the San Luis community and the population at large come from our work. All of this represents an enormous challenge and commitment,” said Eliana Rosales, Director of the Public Health Laboratory of San Luis.

At the hospital, Belén finishes her appointment and prepares to return home. She now has the vaccine to protect her baby against respiratory syncytial virus and feels reassured. Meanwhile, across different parts of the country and throughout the Americas, teams of “virus detectives” remain alert and vigilant, collecting data that help save lives and build more effective responses to respiratory infections.

Closing session of the 2025 evaluation series of sentinel surveillance units for severe acute respiratory infections through the use of PAHO tools.

Argentina

Influenza, SARS-CoV-2, RSV and other respiratory viruses