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.
U.S. virologic surveillance
Nationally, the percentage of respiratory specimens testing positive for influenza virus in clinical laboratories increased (change of ≥ 0.5 percentage points) compared to the previous week. Percent positivity varied by region, with Region 6 the highest (22,5 %) and Region 4 the lowest (13,2 %). A decrease in percent positivity during this time could be due to changes in healthcare seeking behavior or reporting during the holidays rather than an indication that influenza activity has peaked. Influenza A(H1N1)pdm09 and A(H3N2) were the predominant viruses reported this week. 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 2 | Datos acumulativos desde el 29 de sep. del 2024 (semana 40) |
|
|---|---|---|
| Cant. de muestras analizadas | 115 267 | 1 389 448 |
| Cant. de muestras positivas (%) | 21 655 (18,8 %) | 112 302 (8,1 %) |
| Muestras positivas por tipo | ||
| Influenza A | 21 039 (97,2 %) | 108 446 (96,6 %) |
| Influenza B | 616 (2,8 %) | 3 835 (3,4 %) |
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 2 |
Datos acumulativos desde el 29 de sep. del 2024 (semana 40) |
|
|---|---|---|
| Cant. de muestras analizadas | 2 707 | 36 052 |
| Cant. de especímenes positivos | 1 754 | 19 271 |
| Muestras positivas por tipo/subtipo | ||
| Influenza A | 1 719 (98 %) | 18 704 (97,1 %) |
| Subtipificación | 1 440 (83,8 %) | 16 560 (88,5 %) |
| (H1N1)pdm09 | 621 (43,1 %) | 7 513 (45,4 %) |
| H3N2 | 818 (56,8 %) | 8 969 (54,2 %) |
| H3N2v | 0 | 0 |
| H5* | 1 (< del 0,1 %) | 78 (0,4 %) |
| No se realizó clasificación de subtipo | 279 (16,2 %) | 2 144 (11,5 %) |
| Influenza B | 35 (2 %) | 567 (2,9 %) |
| Pruebas de linaje | 16 (45,7 %) | 300 (52,9 %) |
| Línea Yamagata | 0 | 0 |
| Línea Victoria | 16 (100 %) | 300 (100 %) |
| Línea sin determinar | 19 (54,3 %) | 267 (47,1 %) |
*This data reflects 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). No refleja muestras analizadas únicamente en los CDC y podría incluir más de una muestra analizada por persona. Las guías para las pruebas de influenza A/H5 recomiendan tomar hisopados respiratorios y conjuntivales a las personas con conjuntivitis, lo que generó más muestras que dieron positivo para influenza A/H5 que la cantidad de casos de H5 en humanos. For more information on the number of people infected with A/H5, 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)?"
Nuevo virus de influenza A
One confirmed human infection with influenza A(H5) virus was reported to CDC this week. Hasta la fecha, no se ha identificado transmisión entre personas del virus de la influenza A(H5) en Estados Unidos.
This case was reported by the California Department of Public Health and occurred in a child less than 18 years old with no known contact with influenza A(H5N1) virus-infected animals or humans. The investigation into the source of infection for this case is ongoing, and no human-to-human transmission has been identified.
A specimen from the individual was tested at a public health laboratory using the CDC influenza A(H5) assay before being sent to CDC for further testing. The specimen was positive for influenza A(H5) virus using diagnostic RT-PCR at CDC. Additional analysis including genetic sequencing is underway. In response to this detection, additional case investigation and contact monitoring are being conducted by public health officials in California.
There have now been 38 total confirmed human A(H5) cases and one probable human case of A(H5) case in California. This is the second reported pediatric case in California and in the United States.
Notification to WHO of this case was initiated per International Health Regulations (IHR). More information regarding IHR can be found at http://www.who.int/topics/international_health_regulations/en/.
The CSTE position statement, which includes updated case definitions for confirmed, probable, and suspected cases is available at http://www.cste.org/resource/resmgr/position_statements_files_2023/24-ID-09_Novel_Influenza_A.pdf
An up-to-date human case summary during the outbreak by state and exposure source is available at www.cdc.gov/bird-flu/situation-summary/index.html
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.
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 relative to the reference viruses representing the current 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 (https://clades.nextstrain.org).
CDC has genetically characterized 984 influenza viruses collected since September 29, 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 | 491 | ||||
| 5a.2a | 216 (57,3 %) | C.1.9 | 289 (58,9 %) | ||
| 5a.2a.1 | 161 (42,7 %) | D | 14 (2,9 %) | ||
| D.1 | 4 (0,8 %) | ||||
| D.3 | 43 (8,8 %) | ||||
| D.5 | 141 (28,7 %) | ||||
| A/H3 | 739 | ||||
| 2a.3a | 5 (0,9 %) | G.1.3.1 | 5 (0,7 %) | ||
| 2a.3a.1 | 525 (99,1 %) | J.1 | 1 (0,1 %) | ||
| J.1.1 | 5 (0,7 %) | ||||
| J.2 | 676 (91,5 %) | ||||
| J.2.1 | 13 (1,8 %) | ||||
| J.2.2 | 39 (5,3 %) | ||||
| B/Victoria | 103 | ||||
| 3a.2 | 77 (100 %) | C.3 | 1 (1 %) | ||
| C.5 | 15 (14,6 %) | ||||
| C.5.1 | 57 (55,3 %) | ||||
| C.5.6 | 13 (12,6 %) | ||||
| C.5.7 | 17 (16,5 %) | ||||
| B/Yamagata | 0 | ||||
| Y3 | 0 | Y3 | 0 | ||
Los CDC caracterizan antigénicamente los virus de la influenza a través de la inhibición de la hemaglutinación (HI, por sus siglas en inglés) assay (H1N1pdm09, H3N2, and B/Victoria viruses) or neutralization-based HINT (virus H3N2) usando antisuero producido por hurones infectados por los virus de referencia que representaban los virus de referencia de las vacunas de cultivo celular o recombinantes recomendados para el hemisferio norte en el 2024-2025. 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: 51 A(H1N1)pdm09 viruses were antigenically characterized by HI, and 51 (100 %) 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): 63 A(H3N2) viruses were antigenically characterized by HI or HINT, and 25 (39,7 %) 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 or the cell- and recombinant-based influenza vaccines.
Virus de la influenza B
- B/Victoria: 9 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 | CDC.
Viruses collected in the U.S. since September 29, 2024, were tested for antiviral susceptibility as follows:
| Medicamentos antivirales | Virus en total | A/H1 | A/H3 | B/Victoria | ||
|---|---|---|---|---|---|---|
| Inhibidores de neuraminidasa | Oseltamivir | Virus sometidos a prueba | 977 | 384 | 522 | 71 |
| Inhibición reducida | 1 (0,1 %) | 1 (0,3 %) | 0 | 0 | ||
| Inhibición altamente reducida | 0 | 0 | 0 | 0 | ||
| Peramivir | Virus sometidos a prueba | 977 | 384 | 522 | 71 | |
| Inhibición reducida | 0 | 0 | 0 | 0 | ||
| Inhibición altamente reducida | 0 | 0 | 0 | 0 | ||
| Zanamivir | Virus sometidos a prueba | 977 | 384 | 522 | 71 | |
| 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 | 877 | 304 | 511 | 62 |
| Susceptibilidad reducida | 0 | 0 | 0 | 0 | ||
One A(H1N1)pdm09 virus had NA-I223V and NA-S247N amino acid substitutions and showed reduced inhibition by oseltamivir.
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). Por consiguiente, no se recomienda el uso de estos antivirales para el tratamiento y la prevención de las infecciones por el virus de la influenza A y no se presentan datos de análisis de resistencia a la adamantina.
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 2, 5,4 % 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 decreased (change of > 0.1 percentage points) compared to Week 1 but remains above the national baseline of 3 % for the seventh consecutive week. The percentage of visits for ILI remained stable in Region 2 (change of ≤ 0.1 percentage points) and decreased in all other regions (1, 3, 4, 5, 6, 7, 8, 9, and 10) this week compared to last. All regions are above their respective baselines and ILI activity remains elevated across the country. The decreases the past two weeks could be due to changes in healthcare seeking behavior or reporting during the holidays rather than an indication that influenza activity has peaked. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infections to ILI varies by location.
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 (change of > 0.1 percentage point) in all age groups (0-4 years, 5-24 years, 25-49 years, 50-64 years, and 65+ years) in Week 2 compared to Week 1.
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). The state of Vermont is working with CDC to ensure that appropriate data are being used to calculate the state's activity level. Vermont's activity level will be reported again after the issue is resolved.
| Nivel de actividad | Cantidad de jurisdicciones | Cantidad de CBSA | ||
|---|---|---|---|---|
| Semana 2 (Semana que finaliza el 11 de enero del 2025) |
Semana 1 (Semana que finaliza el 4 de enero del 2025) |
Semana 2 (Semana que finaliza el 11 de enero del 2025) |
Semana 1 (Semana que finaliza el 4 de enero del 2025) |
|
| Muy alto | 10 | 20 | 38 | 71 |
| Alto | 25 | 23 | 139 | 191 |
| Moderado | 10 | 5 | 138 | 135 |
| Bajo | 6 | 3 | 188 | 169 |
| Mínimo | 3 | 3 | 197 | 140 |
| Datos insuficientes | 1 | 1 | 229 | 223 |
*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.
National Syndromic Surveillance System (NSSP)
The overall percentage of emergency department (ED) visits with a discharge diagnosis of influenza reported in NSSP was 4,2 % during Week 2. This is a decrease (change of > 0.1 percentage point) compared to the previous week. The percentage also decreased in week 2 compared to the previous week in all 10 HHS regions and among the 0-4, 18-64, and 65+ years age groups. The percentage remained stable (change of ≤ 0.1 percentage point) among the 5-17 years age group. The decreases this week compared to last week could be due to changes in healthcare seeking or reporting during the holidays rather than an indication that influenza activity has peaked.
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 medida que se reciben datos todas las semanas, se actualizan las cantidades y tasas de casos anteriores.
Entre el 1 de octubre del 2024 y el 11 de enero del 2025, los sitios de FluSurv-NET reportaron un total de 9 987 hospitalizaciones por influenza confirmadas en laboratorio. The weekly hospitalization rate observed during Week 2 was 6 per 100 000 population. The weekly hospitalization rate observed during Week 1 (9.6 per 100 000 population) is the second highest peak weekly rate observed, following the 2017-2018 season, across all seasons since 2010-2011. The cumulative hospitalization rate observed in Week 2 was 32.6 per 100 000 population.
Among all hospitalizations, 9 707 (97,2 %) were associated with influenza A virus, 221 (2,2 %) with influenza B virus, 14 (0,1 %) with influenza A virus and influenza B virus co-infection, and 45 (0,5 %) with influenza virus for which the type was not determined. Among those with influenza A subtype information, 1 021 (47,7 %) were A(H1N1) pdm09 and 1 119 (52,2 %) were A(H3N2). When examining rates by age, the highest cumulative hospitalization rate per 100 000 population was among adults aged 65 years and older (98.3), followed by adults aged 50-64 years (36.5), children aged 0-4 years (29.8), adults aged 18-49 (15.3), and children aged 5-17 (9.8).
When examining age-adjusted rates by race and ethnicity, the highest cumulative hospitalization rate per 100 000 population was among non-Hispanic Black persons (49.6), followed by American Indian/Alaska Native persons (44.2), Hispanic persons (31.2), non-Hispanic White persons (25.8), and Asian/Pacific Islander persons (21.8).
National Healthcare Safety Network (NHSN) Hospital Respiratory Data
Hospitals report to NHSN the weekly number of patients with laboratory-confirmed influenza who were admitted to the hospital. Nationally, during Week 2, 31 379 laboratory confirmed influenza-associated hospitalizations were reported. This is a decrease (change of > 5 %) compared to Week 1.
The weekly hospital admission rate observed in Week 2 was 9.3 per 100,000. The weekly rate of hospital admissions in all 10 HHS regions ranged from 6.9 (Region 6) to 15.7 (Region 2). The weekly rate of hospitalizations decreased in all 10 HHS regions. The decrease this week compared to last week could be due to changes in healthcare seeking or reporting during the holidays rather than an indication that influenza activity has peaked.
When examining rates by age for week 2, all age groups decreased this week (change of >5 %) compared to the previous week. The highest hospital admission rate per 100 000 population was among those 75+ years (40.4), followed by 65-to-74-year age group (17.6), and 50-to-64-year age group (10.1).
Vigilancia de mortalidad
National Center for Health Statistics (NCHS)
Based on NCHS mortality surveillance data available on January 16, 2025, 1,5 % of the deaths that occurred during the week ending January 11, 2025 (Week 2), were due to influenza. This percentage increased (> 0.1 percentage point change) compared to Week 1. The data presented are preliminary and may change as more data are received and processed.
Mortalidad infantil asociada a la influenza
Eleven influenza-associated pediatric deaths occurring during the 2024-2025 season were reported to CDC during Week 2. The deaths occurred during weeks 51 and 52 of 2024 and during weeks 1 and 2 of 2025 (the weeks ending December 21 and December 28 of 2024 and January 4 and January 11 of 2025). Las 11 muertes estuvieron asociadas a virus de la influenza A. Six of the influenza A viruses had subtyping performed; three were A(H1N1) viruses, and three were A(H3N2) viruses.
Se reportaron a los CDC 27 muertes pediátricas en total asociadas a la influenza, las cuales ocurrieron durante la temporada 2024-2025.
Información de vigilancia adicional sobre la influenza a nivel nacional e internacional
Estado de los indicadores por sistema
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.
Additional surveillance information
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.
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 .