Lo que necesita saber
Resumen
Virus
Enfermedad
Todos los datos son preliminares y pueden variar a medida que se reciban más informes.
Las flechas direccionales indican los cambios entre la semana actual y la semana previa. Hay información adicional sobre las flechas en la parte inferior de esta página.
A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.1
Hay más información sobre la temporada de influenza actual y la temporada anterior para cada componente de vigilancia disponible en FluView Interactive.
Key Points
• La actividad de la influenza estacional es baja a nivel nacional.
• Percent positivity for influenza and the percentage of emergency department visits for influenza are stable at low levels.
• During Week 40, all 56 viruses reported by public health laboratories were influenza A. Of the 43 influenza A viruses subtyped during Week 40, 24 (55,8 %) were influenza A(H1N1)pdm09 and 19 (44,2 %) were A(H3N2).
• Two human infections with influenza A(H5) virus were reported by the California Department of Public Health.
• No influenza-associated pediatric deaths occurring during the 2024-2025 season were reported to CDC during Week 40.
• CDC recommends that everyone ages 6 months and older get an annual influenza (flu) vaccine, ideally by the end of October.1
• There are prescription flu antiviral drugs that can treat flu illness; those should be started as early as possible and are especially important for higher risk patients.2
• Influenza viruses are among several viruses contributing to respiratory disease activity. Los CDC brindan información actualizada e integrada about COVID-19, flu, and respiratory syncytial virus (RSV) activity on a weekly basis.
U.S. virologic surveillance
Nationally and in HHS regions 1 through 9, the percentage of respiratory specimens testing positive for influenza virus in clinical laboratories remained stable (change of <0.5 percentage points) compared to the previous week. In Region 10, the percent positive increased slightly compared to the previous week. Influenza A(H1N1)pdm09 and A(H3N2) viruses are co-circulating; however, the distribution of circulating viruses varies by region. Para obtener datos a nivel estatal y regional y la distribución de grupos de edad, visite FluView Interactive. Los virus que se sabe que están asociados a la vacunación reciente con la vacuna de virus vivo atenuado (LAIV) o hallados después de pruebas más exhaustivas como virus de vacunas no están incluidos, o no son virus de la influenza en circulación.
Laboratorios clínicos
A continuación se resumen los resultados de las pruebas realizadas por los laboratorios clínicos a nivel nacional. Los datos de laboratorios clínicos (el porcentaje de muestras positivas para virus de la influenza) se utilizan para monitorear si la actividad de la influenza está aumentando o disminuyendo.
| Semana 40 | Semana 39 | |
|---|---|---|
| Cant. de muestras analizadas | 53 699 | 53 424 |
| Cant. de muestras positivas (%) | 380 (0,7 %) | 264 (0,5 %) |
| Muestras positivas por tipo | ||
| Influenza A | 333 (87,6 %) | 208 (78,8 %) |
| Influenza B | 47 (12,4 %) | 56 (21,2 %) |
Laboratorios de Salud Pública
A continuación se resumen los resultados de las pruebas realizadas por laboratorios de salud pública a nivel nacional. Los datos de los laboratorios de salud pública se utilizan para monitorear la proporción de virus de influenza en circulación que pertenecen a cada subtipo/linaje de influenza.
| Semana 40 |
Semana 39 | |
|---|---|---|
| Cant. de muestras analizadas | 638 | 1 113 |
| Cant. de especímenes positivos | 56 | 154 |
| Muestras positivas por tipo/subtipo | ||
| Influenza A | 56 (100 %) | 147 (95,5 %) |
| Subtipificación | 43 (76,8 %) | 135 (91,8 %) |
| (H1N1)pdm09 | 24 (55,8 %) | 69 (51,1 %) |
| H3N2 | 19 (44,2 %) | 66 (48,9 %) |
| H3N2v† | 0 | 0 |
| H5* | 0 | 0 |
| No se realizó clasificación de subtipo | 13 (23,2 %) | 12 (8,2 %) |
| Influenza B | 0 | 7 (4,5 %) |
| Pruebas de linaje | 0 | 7 (100 %) |
| Línea Yamagata | 0 | 0 |
| Línea Victoria | 0 | 7 (100 %) |
| Lineage testing not performed | 0 | 0 |
*These data reflect specimens tested, and the number determined to be positive for influenza viruses at the public health labs (specimens tested is not the same as cases). The data do not reflect specimens tested only at CDC and could include more than one specimen tested per person. The guidance for influenza A/H5 virus testing recommends testing both a conjunctival and respiratory swab for people with conjunctivitis which has resulted in more specimens testing positive for influenza A/H5 virus than the number of human H5 cases. For more information on the number of people infected with A/H5 viruses, please visit the "¿Cómo los CDC están monitoreando los datos de la influenza entre las personas para comprender mejor la situación actual de la influenza aviar A (H5N1)?"
†When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a "variant" influenza virus. La mayoría de las infecciones en seres humanos por variantes del virus de la influenza ocurren después de una exposición a cerdos, pero puede haber contagio entre personas. Es importante destacar que en la mayoría de los casos, las variantes del virus de la influenza no han demostrado tener la capacidad de propagarse fácilmente y de manera continua de persona a persona.
Additional virologic surveillance information for current and past seasons:
Infecciones por el nuevo virus de influenza A
Two human infections with influenza A(H5) viruses were reported to CDC this week by the California Department of Public Health. These cases are associated with an ongoing outbreak of HPAI A(H5N1) virus in dairy cows.
Both individuals are aged >18 years and work at commercial dairy cattle farms where highly pathogenic avian influenza (HPAI) A(H5N1) virus had been detected in cows. These individuals work on different farms and there is no known link or contact between them or between the two cases reported from California last week. These individuals had mild symptoms which they reported to the local health department. Specimens were collected from both persons and were initially tested at the local public health laboratory using the Centers for Disease Control and Prevention (CDC) influenza A(H5) assay before being sent to CDC for further testing. Specimens from both individuals were positive for influenza A(H5) virus using diagnostic rRT-PCR at CDC. Additional analysis including genetic sequencing is underway.
In response to these detections, additional case investigations and surveillance activities are being conducted by public health officials.
Eighteen cases of human infections with influenza A(H5) viruses have been reported in the United States during 2024. Eight of these occurred in individuals working with dairy cows, nine in individuals associated with poultry depopulation and disposal, and one in an individual with an unknown source of exposure. An ongoing outbreak of avian influenza A(H5N1) continues in domestic dairy cows and poultry, and monitoring for additional human cases is ongoing.
Information about avian influenza is available at https://www.cdc.gov/flu/avianflu/index.htm.
Interim recommendations for Prevention, Monitoring, and Public Health Investigations are available at https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html.
The latest case reports on avian influenza outbreaks in wild birds, commercial poultry, backyard or hobbyist flocks, and mammals in the United States are available from the USDA at https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/2022-hpai.
Additional information regarding human infections with novel influenza A viruses:
Caracterización de virus de la influenza
CDC performs genetic y antigenic characterization of U.S. viruses submitted from state and local public health laboratories according to the Right Size Roadmap submission guía. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing the current season's influenza vaccines. Los datos también se utilizan para monitorear los cambios en la evolución que se producen constantemente en los virus de la influenza que circulan en seres humanos. CDC also tests susceptibility of circulating influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the polymerase acidic protein (PA) endonuclease inhibitor baloxavir. The HA clade and subclades were assigned using Nextclade (Nextclade (nextstrain.org).
Los CDC han caracterizado genéticamente 571 virus de la influenza de muestras obtenidas desde el 19 de mayo del 2024.
| Subtipo de virus o linaje | Caracterización genética | ||||
|---|---|---|---|---|---|
| Cantidad total de subtipo/linaje sometida a prueba |
Clado HA |
Cantidad (% de subtipo/linaje sometido a prueba) |
Subclado HA |
Cantidad (% de subtipo/linaje sometido a prueba) |
|
| A/H1 | 197 | ||||
| 5a.2a | 93 (47,2 %) | C.1 | 1 (0,5 %) | ||
| C.1.9 | 92 (46,7 %) | ||||
| 5a.2a.1 | 104 (52,8 %) | C.1.1 | 2 (1 %) | ||
| D | 92 (46,7 %) | ||||
| D.2 | 1 (0,5 %) | ||||
| D.3 | 5 (2,5 %) | ||||
| D.4 | 4 (2 %) | ||||
| A/H3 | 310 | ||||
| 2a.3a | 1 (0,3 %) | G.1.3.1 | 1 (0,3 %) | ||
| 2a.3a.1 | 309 (99,7 %) | J.1 | 10 (3,2 %) | ||
| J.2 | 299 (96,5 %) | ||||
| B/Victoria | 64 | ||||
| 3a.2 | 64 (100 %) | C.5 | 1 (1,6 %) | ||
| C.5.1 | 51 (79,7 %) | ||||
| C.5.6 | 8 (12,5 %) | ||||
| C.5.7 | 4 (6,3 %) | ||||
| B/Yamagata | 0 | ||||
| Y3 | 0 | Y3 | 0 | ||
CDC antigenically characterizes influenza viruses by hemagglutination inhibition (HI) assay (H1N1pdm09, H3N2, and B/Victoria viruses) or neutralization-based HINT (H3N2 viruses) using antisera that ferrets make after being infected with reference viruses representing the 2024-2025 Northern Hemisphere recommended cell or recombinant-based influenza vaccine viruses. Las diferencias antigénicas en los virus se determinan al comparar la capacidad de los anticuerpos generados contra los virus de referencia de la vacuna de reconocer los virus en circulación generados en cultivo celular. Los antisueros de hurones son útiles porque los anticuerpos que se generan contra un virus en particular por lo general pueden reconocer pequeños cambios en las proteínas de la superficie de otros virus. En pruebas de HI, los virus con propiedades antigénicas similares tienen diferencias en la titulación de anticuerpos de menos o igual a 4 veces con respecto al virus de referencia (candidato para la vacuna). Con la HINT, los virus con propiedades antigénicas similares tienen diferencias de titulación de neutralización de anticuerpos menor o igual a 8 veces. Viruses selected for antigenic characterization are a subset of the recent genetically characterized viruses and are chosen based on the genetic changes in their surface proteins and may not be proportional to the number of such viruses circulating in the United States.
Virus de la influenza A
- A (H1N1)pdm09: 54 A(H1N1)pdm09 viruses were antigenically characterized by HI, and 53 (98,1 %) were well-recognized (reacting at titers that were within 4-fold of the homologous virus titer) by ferret antisera to cell-grown A/Wisconsin/67/2022-like reference viruses representing the A(H1N1)pdm09 component for the cell- and recombinant-based influenza vaccines.
- A (H3N2): 118 A(H3N2) viruses were antigenically characterized by HI or HINT, and 95 (80,5 %) were well-recognized (reacting at titers that were within 4-fold of the homologous virus titer in HI or reacting at titers that were less than or equal to 8-fold of the homologous virus in HINT) by ferret antisera to cell-grown A/Massachusetts/18/2022-like reference viruses representing the A(H3N2) component for the cell- and recombinant-based influenza vaccines.
Virus de la influenza B
- B/Victoria: 24 influenza B/Victoria-lineage virus were antigenically characterized by HI, and all were well-recognized (reacting at titers that were within 4-fold of the homologous virus titer) by ferret antisera to cell-grown B/Austria/1359417/2021-like reference viruses representing the B/Victoria component for the cell- and recombinant-based influenza vaccines.
- B/Yamagata: No influenza B/Yamagata-lineage viruses were available for antigenic characterization.
Evaluación de la susceptibilidad del virus a los medicamentos antivirales
Los CDC evalúan la susceptibilidad de los virus de la influenza a los medicamentos antivirales, incluidos los inhibidores de la neuraminidasa (oseltamivir, zanamivir y peramivir) y el inhibidor de la endonucleasa de la subunidad PA (baloxavir), mediante el análisis de secuencias de última generación que se complementa con ensayos de laboratorio. Puede encontrar información sobre los métodos de análisis de susceptibilidad a los antivirales en Vigilancia de la influenza en los EE. UU.: propósito y métodos.
Viruses collected in the United States since May 19, 2024, were tested for antiviral susceptibility are as follows:
| Medicamentos antivirales | Virus en total | A/H1 | A/H3 | B/Victoria | ||
|---|---|---|---|---|---|---|
| Inhibidores de neuraminidasa | Oseltamivir | Virus sometidos a prueba | 559 | 194 | 305 | 60 |
| Inhibición reducida | 0 | 0 | 0 | 0 | ||
| Inhibición altamente reducida | 2 (0,4 %) | 2 (1 %) | 0 | 0 | ||
| Peramivir | Virus sometidos a prueba | 559 | 194 | 305 | 60 | |
| Inhibición reducida | 0 | 0 | 0 | 0 | ||
| Inhibición altamente reducida | 2 (0,4 %) | 2 (1 %) | 0 | 0 | ||
| Zanamivir | Virus sometidos a prueba | 559 | 194 | 305 | 60 | |
| Inhibición reducida | 0 | 0 | 0 | 0 | ||
| Inhibición altamente reducida | 0 | 0 | 0 | 0 | ||
| Inhibidor de la endonucleasa dependiente de la cápsula de la subunidad PA | Baloxavir | Virus sometidos a prueba | 545 | 177 | 304 | 64 |
| Susceptibilidad reducida | 0 | 0 | 0 | 0 | ||
Two A(H1N1)pdm09 viruses had NA-H275Y amino acid substitution conferring highly reduced inhibition by oseltamivir and peramivir.
Altos niveles de resistencia a los adamantanos (amantadina y rimantadina) persisten entre los virus de influenza A (H1N1)pdm09 e influenza A (H3N2) (los adamantanos no son efectivos contra los virus de influenza B). Therefore, use of these antivirals for treatment and prevention of influenza virus infection is not recommended and data from adamantane resistance testing are not presented.
Outpatient and Emergency Department Illness Surveillance
Outpatient respiratory illness visits
The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for respiratory illness referred to as influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and will therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms, including influenza virus, SARS-CoV-2, and RSV. It is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, SARS-CoV-2, and other respiratory virus activity.
Nationally, during Week 40, 1,9 % of patient visits reported through ILINet were due to respiratory illness that included fever plus a cough or sore throat, also referred to as ILI. This week's percentage remained stable (change of ≤ 0.1 percentage points) compared to Week 39 and is below the national baseline of 3 %. All 10 HHS regions are below their respective baselines. The percentage of visits for ILI remained stable in regions 1, 3, 4, 5, 7, 8, and 9, increased slightly in regions 6 and 10, and decreased slightly in region 2 in Week 40 compared to Week 39. Hay varios virus respiratorios en circulación y el aporte relativo de la infección por el virus de la influenza a las ILI varía según el lugar.
Outpatient respiratory illness visits by age group
Aproximadamente un 70 % de los participantes de ILINet informan tanto la cantidad de pacientes que consultaron por enfermedades respiratorias como la cantidad total de pacientes de una semana, clasificadas por grupo de edad. Based on these data, the percentage of visits for respiratory illness decreased for two age groups (0-4 years, 50-64 years) and remained stable (change of ≤ 0.1 percentage point) for three age groups (5-24, 25-49 years, and 65+ years) in Week 40 compared to Week 39.
Outpatient respiratory illness activity map
Los datos recopilados en ILINet se usan para medir la actividad de ILI* por estado/jurisdicción y áreas estadísticas básicas (CBSA).
| Nivel de actividad | Cantidad de jurisdicciones | Cantidad de CBSA | ||
|---|---|---|---|---|
| Semana 40 (Semana que finaliza el 5 de octubre del 2024) |
Semana 39 (Semana que finaliza el 28 de septiembre del 2024) |
Semana 40 (Semana que finaliza el 5 de octubre del 2024) |
Semana 39 (Semana que finaliza el 28 de septiembre del 2024) |
|
| Muy alto | 0 | 0 | 0 | 0 |
| Alto | 0 | 0 | 0 | 2 |
| Moderado | 0 | 0 | 3 | 2 |
| Bajo | 0 | 1 | 29 | 29 |
| Mínimo | 55 | 54 | 672 | 646 |
| Datos insuficientes | 0 | 0 | 225 | 250 |
*La información recopilada por ILINet puede representar desproporcionadamente a ciertas poblaciones dentro de una jurisdicción o CBSA y, por lo tanto, puede no describir con exactitud el panorama completo de la actividad de la influenza para toda la jurisdicción o CBSA. Las diferencias en la información presentada por los CDC y por algunos departamentos de salud probablemente representan distintos niveles de completitud en la información; la información presentada por el departamento de salud probablemente sea la más completa.
Additional information about medically attended visits for ILI for current and past seasons:
National Syndromic Surveillance System (NSSP)
The percentage of emergency department (ED) visits with a discharge diagnosis of influenza reported in NSSP was 0,2 % overall during Week 40. This week's percentage remained stable overall and among all age groups compared to the previous week.
Additional information about emergency department visits for flu for current and past seasons:
Vigilancia de hospitalización
FluSurv-Net
La Red de Vigilancia de Hospitalizaciones por Influenza (FluSurv-NET) lleva adelante tareas de vigilancia basadas en la población para detectar hospitalizaciones relacionadas con la influenza, y confirmadas por laboratorio, en determinados condados en 14 estados y representa aproximadamente el 9 % de la población estadounidense. Los datos de hospitalizaciones en FluSurv-NET son preliminares.
A total of 15 laboratory-confirmed influenza-associated hospitalizations were reported by FluSurv-NET sites between October 1 (the start of FluSurv-NET enrollment for the 2024-2025 season) and October 5, 2024. La tasa de hospitalizaciones observada en la semana 40 fue de 0.0 por cada 100 000 habitantes.
Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
National healthcare safety network (NHSN) hospitalization surveillance
Effective November 1, 2024, all acute care and critical access hospitals will be required to report the number of patients admitted with laboratory-confirmed influenza to NHSN. These data will be updated weekly in FluView and on FluView Interactive once sufficient data has been collected. Public datasets, including data reported on a voluntary basis prior to November 1, can be found here: https://data.cdc.gov/Public-Health-Surveillance/Weekly-United-States-Hospitalization-Metrics-by-Ju/aemt-mg7g/about_data.
Additional NHSN Hospitalization Surveillance information:
Vigilancia de mortalidad
Based on NCHS mortality surveillance data available on October 10, 2024, 0,06 % of the deaths that occurred during the week ending October 5, 2024 (Week 40), were due to influenza. This percentage remained stable (≤ 0.1 percentage point change) compared to week 39. Los datos presentados son preliminares y pueden cambiar a medida que se reciba y se procese más información.
Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
Mortalidad infantil asociada a la influenza
No se han reportado a los CDC muertes pediátricas asociadas a la influenza durante la temporada 2024-2025.
Additional pediatric mortality surveillance information for current and past seasons:
Información de vigilancia adicional sobre la influenza a nivel nacional e internacional
En aumento: 
En disminución: 
Estable: 
Clinical Labs: Up or down arrows indicate a change of greater than or equal to 0.5 percentage points in the percent of specimens positive for influenza compared to the previous week.
Enfermedad respiratoria en pacientes ambulatorios (ILINet): las flechas ascendentes y descendentes indican un cambio igual o mayor a 0.1 punto porcentual en el porcentaje de visitas debido a una enfermedad respiratoria (ILI) en comparación con la semana previa.
Hospitalizaciones en NHSN: las flechas ascendentes y descendentes indican un cambio igual o mayor al 5 % de la cantidad de pacientes hospitalizados con influenza confirmada en laboratorio en comparación con la semana anterior.
Mortalidad del NCHS: las flechas ascendentes y descendentes indican un cambio igual o mayor a 0.1 puntos porcentuales del porcentaje de muertes por influenza en comparación con la semana anterior.
FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. Estas aplicaciones interactivas de FluView Interactive permiten a las personas crear interpretaciones visuales personalizadas de los datos sobre la influenza, además de hacer comparaciones entre las temporadas de influenza, las regiones, los grupos de edad y una variedad de otros datos demográficos.
National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.
U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information.
Organización Mundial de la Salud:
Hay información adicional de vigilancia de la influenza generada por naciones participantes que forman parte de la OMS disponible a través de FluNet y la Informes de epidemiología mundial.
Centros de colaboración de la OMS para la influenza:
Australia, China, Japón, el Reino Unido y los Estados Unidos (CDC en Atlanta, Georgia)
Europa:
La información más actualizada sobre la influenza en Europa está disponible a través de la OMS/Europa y los Centros para el Control y la Prevención de Enfermedades de Europa.
Agencia de Salud Pública de Canadá:
La información más actualizada sobre la influenza en Canadá está disponible en Informe semanal FluWatch de Canadá.
Salud Pública de Inglaterra:
La información más actualizada sobre la influenza en el Reino Unido está disponible a través de Salud Pública de Inglaterra.
Todos los enlaces a organizaciones que no pertenecen al Gobierno Federal se brindan únicamente como un servicio a nuestros usuarios. Estos enlaces no constituyen un aval a estas organizaciones o a sus programas por parte de los CDC o el Gobierno Federal, y no debería hacerse inferencia alguna al respecto. Los CDC no son responsables del contenido que se encuentra en los enlaces de los sitios web de cada una de las organizaciones.
Hay una descripción del sistema de vigilancia de la influenza de los CDC, incluida su metodología y las descripciones detalladas de cada componente, disponible en la página de métodos de vigilancia .
- U.S. Influenza Surveillance: Purpose and Methods (2023 Oct). Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/overview.htm#ILINet.
- Influenza Antiviral Medications: Summary for Clinicians (2023 Sept). Centers for Disease Control and Prevention. https://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm.