Epidemiological alert Influenza, respiratory syncytial virus and SARS-CoV-2

Pan American Health Organization PAHO and World Health Organization WHO June 6, 2023

Considering the increased activity of respiratory viruses at pre-pandemic levels and the associated hospitalizations predominantly among children under 2 years of age, in the Andean subregion and the southern cone, the Pan American Health Organization / World Health Organization (PAHO/WHO ) recommends that Member States strengthen and integrate surveillance of influenza, Respiratory Syncytial Virus (RSV) and SARS-CoV-2 and adopt the necessary measures for the prevention and control of severe cases, ensuring high coverage of vaccination in high-risk groups, adequate clinical management, adequate organization of health services, strict compliance with infection prevention control measures, adequate supply of antivirals, and timely treatment of associated complications.

Summary of the situation

The following is a summary of the influenza situation by subregion in the Region of the Americas 1 . The status of the southern subregion, which has shown an early rise in seasonal influenza and increased RSV activity, is listed first, followed by the Andean and Central America subregions, where influenza activity has been maintained at low levels and VRS has increased. Country information is summarized in alphabetical order after the subregional summary. Next, the situation of the other subregions with planned activity is presented in alphabetical order. More detailed information on influenza and other respiratory viruses can be obtained from the PAHO/WHO Regional Update on Influenza, published weekly on the PAHO/WHO website at: https://www.paho.org/en/report - situation-influenza

In the Andean subregion (Bolivia, Colombia, Ecuador, Peru and Venezuela) , as of EW 19 of 2023, influenza activity has shown an increase in detections with stable low levels of positivity. During the last 4 EWs, influenza A(H1N1)pdm09 predominated, followed by influenza B (Victoria). RSV activity has increased and remained at medium circulating levels, while SARS-CoV-2 was circulating at moderate levels. SARI activity has remained consistently high, with influenza accounting for more than half of cases, and among the 20-59 age group, followed by RSV among the less than 5 age group.

WHO and PAHO epidemiological alert


Taking into account the increase in activity and hospitalizations caused by seasonal influenza, RSV, and SARS-CoV-2 in the region, PAHO/WHO reiterates its recommendations to Member States regarding surveillance, prevention, immunization against influenza and COVID-19, clinical management of patients, proper organization of health services, implementation of infection control and prevention measures in health services, and communication with the public about preventive measures . It is essential to address these areas taking into account the current season in the countries of the southern hemisphere.

Below is a summary of the main recommendations for surveillance, clinical management, risk communication, and vaccination.


PAHO/WHO recommends that Member States integrate surveillance of influenza, RSV, SARS-CoV-2, and other respiratory viruses into existing national platforms and report surveillance data to the Global Influenza Surveillance and Response System ( GISRS) through the FluNET and FluID platforms.

Member States are recommended to continue strengthening ILI surveillance and prioritize SARI surveillance complemented by other surveillance strategies 10 to monitor epidemiological changes and viral circulation trends to assess transmission patterns, clinical severity, and the impact on the health system and society, and identify groups at risk of developing associated respiratory complications.
As a complement to indicator-based surveillance, PAHO/WHO recommends that Member States implement event-based surveillance. Event-based surveillance is the organized and rapid capture of information about events that may represent a potential risk to public health. The information may come from rumors and/or other ad-hoc reports transmitted through formal routine information systems (pre-established routine information systems) or informal-non-pre-established (ie, media, direct communication from health workers or non-governmental organizations). Event-based surveillance is a functional component of the early warning and response mechanism11. Respiratory events that are unusual should be investigated immediately. Unusual events include cases of influenza with atypical clinical progression; acute respiratory infection associated with exposure to sick animals, or observed in travelers from areas prone to the emergence of novel influenza viruses; SARI cases in health professionals; or clusters of influenza viral infections outside of the typical circulation season.
As part of routine indicator-based surveillance, and for etiologic confirmation of unusual cases, nasopharyngeal and oropharyngeal swabs (or bronchial lavage, in severe cases) should be obtained for respiratory virus detection. Laboratory analysis of the most serious cases should always be prioritized, especially those admitted to ICUs and fatal cases (deaths) in which it is also recommended to take tissue samples from the respiratory tract (if possible). All biosecurity measures for respiratory pathogens must be taken. The technical guidelines and diagnostic algorithms of the National Influenza Center or the national reference laboratory responsible for laboratory surveillance should be followed14. Recommended testing algorithms for influenza, RSV, and SARS-CoV-2 are available at: Influenza and Other Respiratory Viruses - PAHO/WHO | Pan American Health Organization (paho.org)
In accordance with WHO guidelines12, positive influenza specimens from severe cases or unusual presentations should be sent to the PAHO/WHO Collaborating Center (CC) in the US Center for Disease Control and Prevention ( CDC) in Atlanta for proper characterization. Influenza A samples, for which the virus subtype cannot be determined (those positive for Influenza A but where the PCR for subtyping is negative or inconclusive), should also be sent immediately to the PAHO/WHO CC. at the US CDC Influenza-positive animal specimens should be sent to the PAHO/WHO CC at St. Jude Hospital in Memphis, Tennessee, USA, for further characterization.

Clinical management
The recommendations for the clinical management of patients with severe respiratory disease indicated in the epidemiological alerts and in the PAHO/WHO updates on influenza are still valid. Groups at highest risk for complications related to influenza infection include children under two years of age; adults over 65 years of age; pregnant or postpartum women; people with underlying clinical morbidity (eg, chronic lung disease, asthma, cardiovascular disease, chronic kidney disease, chronic liver disease, diabetes mellitus, neurological conditions such as central nervous system lesions, and delayed cognitive development); people with immunosuppression (for example, HIV / AIDS or due to medications); and people with morbid obesity (body mass index greater than 40).
Anyone with severe or progressive clinical presentation of respiratory illness should be treated with antivirals as soon as influenza is suspected or treated according to recent guidelines for suspected COVID-1913. Treatment should be started even before there is laboratory confirmation of influenza infection, since treatment is more successful if started early. In persons with suspected or confirmed influenza virus infection at risk of severe illness (ie, including seasonal influenza, pandemic influenza, and zoonotic influenza), we suggest administering oseltamivir as soon as possible. We suggest not administering inhaled zanamivir, inhaled laninamivir, intravenous peramivir, corticosteroids, passive immunotherapy macrolide antibiotics for the treatment of influenza.
In settings where batch RT-PCR or other rapid molecular assays for influenza (with similarly high sensitivity and specificity) are available and results are expected within 24 hours, we suggest a strategy of testing for influenza, administer oseltamivir treatment as soon as possible and reassess treatment when test result is available.
In settings where batch RT-PCR or other rapid molecular assays for influenza (with similarly high sensitivity and specificity) are not available for a result within 24 hours, we suggest a strategy in which get tested for influenza and administer oseltamivir as soon as possible.
For more details, see the guidelines "Guidelines for the clinical management of severe illness from influenza virus infections". Geneva: World Health Organization; 2021", available in English: https://apps.who.int/iris/handle/10665/352453; and Clinical care of severe acute respiratory infections – Tool kit (who.int).
Guidelines for the clinical management of COVID-19, including the use of antivirals, monoclonal antibodies, and other interventions for the management of patients with COVID-19 are available at: PAHO Technical Documents - Coronavirus Disease (COVID-19) - PAHO/WHO | Pan American Health Organization (paho.org) and Clinical management of COVID-19 (who.int).

When it comes to clinical treatment and RSV prophylaxis, young infants are at increased risk of severe complications and hospitalization for RSV infection and represent the greatest burden of disease. Many of the risk factors for RSV infections are similar to those identified for all causes of lower respiratory tract infections. There is no effective treatment and supportive care remains the cornerstone of clinical treatment. Currently, treatment for RSV infections is symptomatic and there are no effective antiviral drugs. Passive immunization with monoclonal antibodies -palivizumab- is an appropriate intervention to reduce severe acute respiratory infection by RSV in infants at risk.
Palivizumab prophylaxis was associated with a 43% reduction in the rate of RSV-related hospitalizations in children with hemodynamically significant congenital heart disease and a reduction in recurrent wheezing. The cost and method of administration of the drug remain a challenge, although its cost-effectiveness is well documented.
Recently, two RSV vaccines for older adults were approved by the US Food and Drug Administration (FDA)1415 for use in the United States for the prevention of RSV lower respiratory tract illness in people 60 years and older. In randomized clinical trials, the vaccines reduced the risk of developing RSV-associated lower respiratory tract infections by 66.7%-6% and reduced the risk of developing RSV-associated serious lower respiratory tract infections by 94.1%. .16 Currently, there has been a resurgence in vaccine development (vaccine candidates and long-acting immunoprophylaxis with monoclonal antibodies) along with significant progress in understanding immune responses to RSV.
Key recommendations for the management of RSV17 18 19 include:
• The diagnosis of bronchiolitis and the assessment of the severity of the disease should be based on the history and physical examination. Laboratory and radiological studies should not be routinely requested for diagnosis.
• Risk factors for severe disease, such as age less than 12 weeks, history of preterm birth (particularly less than 32 weeks), underlying cardiopulmonary disease (including bronchopulmonary dysplasia and hemodynamically significant congenital heart disease), neuromuscular disorders or immunodeficiencies should be considered when making decisions about the evaluation and treatment of children with bronchiolitis.
• Bronchodilators (albuterol, salbutamol), epinephrine, and corticosteroids should not be given to infants and children diagnosed with bronchiolitis. Also, nebulized hypertonic saline should not be administered to children diagnosed with bronchiolitis in the emergency department. Nebulized hypertonic saline can be given to infants and children hospitalized for bronchiolitis.
• Antibiotics should not be used in children with bronchiolitis unless there is a concomitant bacterial infection.
• Palivizumab prophylaxis should be administered during the first year of life to infants with hemodynamically significant heart disease or chronic lung disease of prematurity (<32 weeks' gestation requiring >21% O2 during the first 28 days of life).
• To prevent spread of respiratory syncytial virus (RSV), hands should be decontaminated before and after direct contact with patients, after contact with inanimate objects in the vicinity of the patient, and after glove removal. Alcohol is the preferred method for hand decontamination. Clinicians should educate staff and family about hand sanitation.
• Babies should not be exposed to tobacco smoke.
• Exclusive breastfeeding is recommended for at least 6 months to
reduce the morbidity of respiratory infections.
risk communication
Seasonal influenza is an acute viral infection that is easily transmitted from person to person. Seasonal influenza viruses circulate throughout the world and can affect anyone in any age group. Influenza vaccination before the onset of seasonal virus circulation remains the best preventive measure against severe influenza.
The public should be informed that the primary mode of transmission of influenza is interpersonal contact. Hand washing is the most efficient way to decrease transmission. Knowledge about "respiratory etiquette" also helps prevent transmission.
People with a fever should avoid going to workplaces or public places until the fever subsides. Similarly, school-age children with respiratory symptoms, fever, or both should stay home from school.
In order to take advantage of the knowledge that the majority of the public has acquired on the prevention of respiratory diseases -as a result of the COVID-19 pandemic-, and to avoid confusion and exercise effective communication, Member States should consider developing strategies and campaigns of risk communication that integrates prevention messages for both viruses. The integration of communication for the promotion of vaccination against COVID-19 and influenza is also recommended.
Immunization is an important strategy to prevent serious outcomes of seasonal influenza and COVID-19, including associated hospitalizations and deaths.
PAHO/WHO recommends vaccination of groups at particular risk of severe influenza, including older adults, people with underlying health conditions, children younger than 59 months, and pregnant women. Healthcare workers are at increased risk of exposure to and transmission of the influenza virus and SARS-CoV-2 and therefore should also be given priority.
In addition to vaccination, personal measures such as hand hygiene, physical distancing, respiratory etiquette, mask use, and staying home when sick, which are effective in limiting the transmission of respiratory viruses, should be observed12.
Non-pharmacological measures of public health in the population
As recently evidenced during the COVID-19 pandemic, non-pharmacological public health measures complement the response to respiratory events.
For more details, see the guidelines: "Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza", available in English at: Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza (who.int), and the "Guide for the implementation of non-pharmacological public health measures in vulnerable populations in the context of COVID-19-PAHO/OMS", available in English at: Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza (who.int)
related links
• Statement on the thirteenth meeting of the International Health Regulations Emergency Committee (2005) regarding the coronavirus disease (COVID-19) pandemic.
• End-to-End Integration of SARS-CoV-2 and Influenza Sentinel Surveillance: Revised Interim Guidance
• Final report Ad hoc Consultation of experts in the Region of the Americas: Challenges, gaps, and next steps in the surveillance of COVID 19 and its integration in the surveillance of influenza and other respiratory viruses
Pan American Health Organization • www.paho.org • © PAHO/WHO, 2023

• PAHO/WHO epidemiological alerts on influenza are available at: https://www.paho.org/es/alertas-actualizaciones-epidemiologicas
• https://www.who.int/teams/global-influenza-programme/surveillance-and-monitoring/influenza-updates
• Influenza situation reports. Pan American Health Organization / World Health Organization. Available at: https://www.paho.org/es/informe-situacion-influenza.
• Manual for laboratory diagnosis and virological surveillance of influenza. 2011. Available at: https://apps.who.int/iris/handle/10665/44518
• World Health Organization. Early detection, assessment and response to acute public health events: Implementation of Early Warning and Response with a focus on Event-Based Surveillance. Interim Version. WHO/HSE/GCR/LYO/2014.4. Geneva: WHO: 2014. Available at: https://apps.who.int/iris/handle/10665/112667)
• PAHO Technical Documents - Coronavirus Disease (COVID-19): https://www.paho.org/es/documentos-tecnicos-ops-enfermedad-por-coronavirus-covid-19.
Clinical management
• Clinical Care of Severe Acute Respiratory Infections - Toolkit
• Guide for the care of critical adult patients with COVID-19 in the Americas.
Abstract, version 3. https://iris.paho.org/handle/10665.2/53894
• Considerations on the use of antivirals, monoclonal antibodies and other
interventions for the management of patients with COVID-19 in Latin America and the
Caribbean. https://iris.paho.org/handle/10665.2/55968?locale-attribute=es
• Guidelines for the clinical management of severe illness from influenza virus infections.
Geneva: World Health Organization; 2021
• Recommended composition of influenza virus vaccines for use in
the 2022-2023 northern hemisphere flu season.
Human-animal interface
• Avian influenza (who.int)
• World Organization for Animal Health (wahis.woah.org)
• News about disease outbreaks (who.int)
• Influenza Situation Report | PAHO/WHO | Pan American Organization of the
Health (paho.org)
• Weekly update of avian influenza number 869 (H5). (who.int)
• Influenza at the human-animal interface. PAHO recommendations to strengthen
intersectoral work in surveillance, early detection and research, 9
July 2020. https://iris.paho.org/handle/10665.2/52562
• Summary and Assessment of Influenza at the Human-Animal Interface, October 5, 2022.
WHO and PAHO epidemiological alert
Back to blog