Influenza aviar H5N1. ¿Debemos preocuparnos? / Avian influenza H5N1. Should we worry?

Desde la segunda mitad de 2022 se ha reportado un aumento de casos de influenza en aves migratorias en Latinoamérica. Los virus influenza A y B son los principales agentes asociados a influenza estacional epidémica en humanos. Los virus influenza A circulan no solo en humanos sino también en animales, incluyendo aves migratorias. El intercambio de segmentos de ARN genómico entre dos virus del mismo tipo aumenta la diversidad de los subtipos circulantes e incluso puede facilitar la generación de progenie viral potencialmente pandémica. La naturaleza zoonótica del virus influenza A puede generar infecciones en humanos con virus de origen animal. El virus influenza A de origen aviar ha ocasionado transmisiones en humanos, incluyendo casos graves y muertes, siendo la influenza A H5N1 la más destacada. Es importante tomar medidas de prevención y control en caso de aumento de casos de influenza en aves migratorias para prevenir posibles pandemias en Chile y el mundo.

Since the second half of 2022, an increase in influenza cases in migratory birds has been reported in Latin America. Influenza A and B viruses are the main agents associated with seasonal epidemic influenza in humans. Influenza A viruses circulate not only in humans but also in animals, including migratory birds. The exchange of genomic RNA segments among two viruses increases the diversity of circulating subtypes and may even facilitate the generation of potentially pandemic viral progeny. The zoonotic nature of influenza A virus can generate infections in humans with animal-origin viruses. Avian-origin influenza A virus has caused transmissions in humans, including severe cases and deaths, with influenza A H5N1 being the most prominent. It is important to take preventive and control measures in case of an increase in influenza cases in migratory birds to prevent possible pandemics in Chile and the world.

Avian influenza A (H7N9) virus: from low pathogenic to highly pathogenic / 医学前沿

The avian influenza A (H7N9) virus is a zoonotic virus that is closely associated with live poultry markets. It has caused infections in humans in China since 2013. Five waves of the H7N9 influenza epidemic occurred in China between March 2013 and September 2017. H7N9 with low-pathogenicity dominated in the first four waves, whereas highly pathogenic H7N9 influenza emerged in poultry and spread to humans during the fifth wave, causing wide concern. Specialists and officials from China and other countries responded quickly, controlled the epidemic well thus far, and characterized the virus by using new technologies and surveillance tools that were made possible by their preparedness efforts. Here, we review the characteristics of the H7N9 viruses that were identified while controlling the spread of the disease. It was summarized and discussed from the perspectives of molecular epidemiology, clinical features, virulence and pathogenesis, receptor binding, T-cell responses, monoclonal antibody development, vaccine development, and disease burden. These data provide tools for minimizing the future threat of H7N9 and other emerging and re-emerging viruses, such as SARS-CoV-2.

Cholera outbreak continues in Yemen

Yemen has been experiencing a cholera outbreak that started in early August 2016. As of 1 February, 2017, a cumulative number of 18, 848 suspected Cholera cases including 97 associated deaths [case fatality rate 0.86%] have been reported from 157 districts in 15 governorates

Avian Influenza A [H5N1]: new cases reported in Egypt

During the month of February, the Ministry of Health and Population in Egypt reported two new human cases of Avian Influenza A [H5N1] including one death to WHO. These two cases are reported for the first time in 2017. Since March 2006, Egypt reported a total of 358 laboratory confirmed cases of Avian Influenza A [H5N1] including 122 deaths [CFR: 34.08%]

Evaluación in silico de una epidemia de influenza aviar AH5N1 con transmisión humano-humano: efecto de las medidas sanitarias en Valencia, Venezuela, 2012 / In silico evaluation of an aviar influenza AH5N1 virus outbreak with human to human transmission: effects of sanitary measures in Valencia, Venezuela, 2012

Introducción: Existe el riesgo de una pandemia de influenza aviar por virus AH5N1. Objetivo: Conocer la magnitud e impacto en áreas latinoamericanas de una pandemia AH5N1 a fin de planificar las medidas sanitarias para reducir la morbimortalidad. Material y Método: Mediante el simulador InfluSim se modeló una epidemia por virus AH5N1 con transmisión Humano-Humano, en Valencia, Venezuela. Se calculó el día de máximo número de casos, cantidad de enfermos moderados, graves, expuestos, muertos, y costos en cinco escenarios diferentes: sin intervención sanitaria; tratamiento antiviral; reducción en 20% del contacto en la población; cierre de 20% de las instituciones educativas; reducción de 50% de las reuniones públicas. Parámetros usados: Población: 829.856 habitantes, Porcentaje de riesgo 6-47%, Contagiosidad índice (Ro) 2,5; Contagiosidad relativa 90%, Tasa de letalidad global 64,1 %, costos según Canasta Básica oficial. Resultados: En 200 días de epidemia: Muertes totales por escenario: a: 29.907; b: 29.900; c: 9.701; d: 29.295 y d: 14.752. Similar tendencia en costos. Discusión: Reducir 20% los contactos de la población produjo una reducción significativa de 68% en el número de casos. La epidemia colapsará los sistemas de salud disponibles por cantidad de casos. El tratamiento antiviral no es eficiente durante la epidemia. La reducción en los contactos interpersonales muestra ser la mejor medida sanitaria.

Background: There is a risk for an avian influenza AH5N1 virus pandemia. Aim : To estimate the magnitude and impact of an AH5N1 pandemic in areas of Latin-America in order to design interventions and to reduce morbidity-mortality. Methods : The InfluSim program was used to simulate a highly pathogenic AH5N1 aviar virus epidemic outbreak with human to human transmission in Valencia, Venezuela. We estimated the day of maximal number of cases, number of moderately and severely ill patients, exposed individuals, deaths and associated costs for 5 different interventions: absence of any intervention; implementation of antiviral treatment; reduction of 20% in population general contacts; closure of 20% of educational institutions; and reduction of 50% in massive public gatherings. Simulation parameters used were: population: 829.856 persons, infection risk 6-47%, contagiousness Index Rh o 2,5; relative contagiousness 90%, overall lethality 64,1% and, costs according to the official basic budget. Results: For an outbreak lasting 200 days direct and indirect deaths by intervention strategies would be: 29,907; 29,900; 9,701; 29,295 and 14,752. Costs would follow a similar trend. Discussion: Reduction of 20% in general population contacts results in a significant reduction of up to 68% of cases. The outbreak would collapse the health care system. Antiviral treatment would not be efficient during the outbreak. Interpersonal contact reduction proved to be the best sanitary measure to control an AH5N1 theoretical epidemic outbreak.

Avaliação situacional de influenza pós pandemia de 2009 - uma breve revisão / Situational assessment of influenza post 2009 Pandemic - a brief review

Os vírus influenza são responsáveis por epidemias anuais com gravidade da doença variável. Causam infecção respiratória aguda com elevada transmissibilidade devido sua alta variabilidade genética, capacidade de adaptação e rápida disseminação. Os vírus influenza apresentam genoma fragmentado,o que ocasiona variações antigênicas frequentes, e consequentemente pode induzir o aparecimento de subtipos mais virulentos, como ocorreu em 2009,quando foi registrada pandemia por um novo vírus Influenza A H1N1. A Organização Mundial de Saúde(OMS) estima que a gripe acometa 5 a 15% da população,ocasionando 3 a 5 milhões de casos graves e 250.000 a 500.000 mortes anualmente. As epidemias anuais de gripe e o risco de novas pandemias tornamo monitoramento epidemiológico do vírus influenza fundamental e, para isto, a OMS coordena a Rede Mundial de Vigilância da Influenza com a finalidade de fornecer informações necessárias para a escolha das variantes virais que farão parte da composição anual da vacina, visto que a vacinação é uma das medidas mais efetivas para prevenção da gripe e suas complicações. Além disso, a rede constitui uma vigilância rápida para identificações de vírus influenza emergentes com potencial epidêmico ou pandêmico.Esta vigilância é viabilizada pelos resultados dos testes laboratoriais que são ferramentas importantes para a Saúde Pública, sendo fundamentais para a contenção e prevenção dos vírus circulantes. O objetivo deste estudo foi apresentar informações relacionadas ao vírus influenza e a doença, como são realizados o diagnóstico e monitoramento pelas redes de vigilâncias mundiais pós-pandemia e, ainda, quais os novos desafios que se apresentam.

Influenza viruses are responsible for annual epidemics with patients presenting variable degrees of diseases everity. These virus can cause acute respiratory infection with a high transmissibility due to its high genetic variability, adaptability and rapid spread. Influenza viruses have fragmented genome which causes frequent antigenic variation, which can result in more virulent subtypes emergence, as occurred in 2009 when it was described a new pandemic influenza virus H1N1. WHO estimates that flu affects 5-15% of the population and it causes 3 to 5 million of severe cases and 250.000 to 500.000 deaths annually. The annual influenza epidemics and the new pandemics risk high lights the importance of Influenza virus epidemiological monitoring. Based in this concern WHO created and coordinates the Global Influenza Surveillance and Response System in order to provide necessary information for viral variants selection that will be part of vaccine annual composition, since that, vaccination is one of the most effective measures for influenza prevention and its complications. In addition, the network is a rapid surveillance of emerging influenza virus identifications with potential to cause epidemic or pandemic situations. The surveillance isenable due to laboratory tests results which are important tools for public health, with essential role for circulating viruses containment and prevention. The aim of this study was to present information related to influenza virus and flu disease, how the diagnosis and monitoring are performed by global surveillance networks at post pandemic time and, also,the new challenges facing.

Ações de vigilância para influenza aviária desenvolvida no Brasil, no período de 2004 e 2007 / Avian influenza surveillance activities, developed in Brazil from 2004 to 2007

No início dos anos 2000, o Brasil se consolidou como maior exportador mundial de carne de frango, mesmo período em que se observou a emergência global de focos de HPAI. Para assegurar a qualidade sanitária do produto avícola nacional, o Mapa organizou um programa oficial de vigilância para o vírus de IA. Na primeira fase, foram coletados 106.226 soros e 7.017 pools de suabes traqueais e cloacais, provenientes de granjas avícolas de produção comercial intensiva de frangos de corte, no período entre janeiro de 2004 e março de 2005. Não se obteve isolamento viral para IA, porém foi identificado um conglomerado epidemiológico de 24 municípios, delineado pela interpolação de dados relacionados às localizações geográficas, e os resultados sorológicos das amostras dessas origens, ELISA reagente para IA, no estado de Rondônia. Na segunda fase da vigilância, três distintas ações para pesquisa do vírus de IA foram executadas entre 2006 e 2007, em: 1) aves comerciais de corte de criação intensiva; 2) aves de reprodução; e 3) aves migratórias e de subsistência. Não houve identificação de resposta sorológica ou isolamento de vírus de IA em aves dos grupos 1 e 2. Foram isolados vírus de IA do subtipo H3 em aves migratórias, capturadas nos estados de Pará e Pernambuco. Também foram identificados vírus de IA dos subtipos H2, H3 e H4 em aves de subsistência, de propriedades localizadas no Amazonas, Pará, Pernambuco, Rio Grande do Sul e Santa Catarina. Observou-se risco sanitário para LPAI associado às populações de aves silvestres e de subsistência localizadas em áreas próximas ao sistema comercial. Estudos adicionais serão necessários para se avaliar o risco associado à introdução de IA no sistema comercial avícola brasileiro.

In the early 2000s Brazil had established itself as the world's largest exporter of poultry meat, the same period in which the emergence of HPAI global outbreaks was observed. To ensure the national health quality of Brazilian poultry product, MAPA organized an official AI surveillance program. In the first stage, during the period between January 2004 and March 2005, 106.226 sera were collected and 7.017 tracheal and cloacae pools of swabs were obtained from intensive commercial broiler farms. No AI virus isolation was obtained, however, an epidemiological cluster was identified in the state of Rondonia, outlined by the interpolation of data related to municipalities' geographic location and serological response to AI in ELISA tests. Between 2006 and 2007, during the second stage, three AI surveillance actions were executed in: 1) intensive commercial broiler farms, 2) breeding farms and 3) migratory and backyard birds. There was neither serological response identification nor IA virus isolation in birds belonging to groups 1 and 2. H3 LPAI subtype viruses were isolated from migratory birds captured in the states of Pará and Pernambuco. H2, H3 and H4 LPAI subtypes were also identified in backyard birds from samples collected in the states of Amazonas, Pará, Pernambuco, Rio Grande do Sul and Santa Catarina. There are health risks to LPAI associated to wild and backyard bird populations located in areas close to commercial farms. Additional studies are needed for risk assessment regarding the possibility of AI introduction in the Brazilian commercial poultry system.

Brote de influenza A (H1N1) humano en pavos en un criadero comercial, Valparaíso, Chile: 2009 / Outbreak of human A (H1N1) influenza in turkeys of a commercial poultry farm, Valparaiso, Chile: August 2009

The Chilean Ministry of Health (MINSAL) led an investigation to identify associated factors to human influenza A (H1N1) infection in turkeys from poultry farms, Valparaíso. The Agriculture and Livestock Farming Service (SAG) informed the detection of influenza A (low pathogenicity) in turkeys and the Public Health Institute (ISP) confirmed influenza A (H1N1).The study included 100% of operative wards: 31% presented positive event (influenza A (H1N1)); 60% if considered only reproductive wards. Dissemination and dispersion velocity of 13 wards in 18 days evidenced a continuous common source. Interviews were performed to 89% of workers of whom 20% presented influenza-like disease: 26% from reproductive wards and 4% from raising and rearing farms. Of15 risk factors studied insemination and age in females showed statistically significant RR in low oviposition index wards. A man-bird transmission is proposed, through direct transmission of saliva during manual insemination or indirect transmission through contaminated semen. To the authors, this is the first turkey 2009 influenza H1N1 outbreak detected worldwide,in this case with a documented cloacal transmission path.

El MINSAL lideró una investigación para identificar factores asociados a infección por influenza A(H1N1) en pavos de planteles avícolas, Valparaíso. El Servicio Agrícola Ganadero informó la detección de influenza A (baja patogenicidad) en pavos y el ISP confirmó influenza A(H1N1). El estudio incluyó 100% de los pabellones operativos: 31% presentó evento positivo (influenza A(H1N1); 60% al considerar sólo pabellones de reproducción. La diseminación y velocidad de dispersión de 13 pabellones en 18 días evidenció una fuente común continua. Se entrevistó a 89% de los trabajadores y 20% presentó ETI: 26% de pabellones de reproducción y 4% de granjas de cría y recría. De 15 factores analizados, inseminación y edad de las hembras mostraron RR estadísticamente significativos en los planteles con baja ovipostura. Se plantea transmisión hombre-ave directa por saliva en inseminación manual o transmisión indirecta por semen contaminado. Es el primer brote de influenza A(H1N1) 2009 en pavos detectado en el mundo y que se comprueba vía de transmisión cloacal.

Estratificación epidemiológica del riesgo de las enfermedades emergentes y reemergentes por áreas de salud. Provincia de Matanzas, 2002-2006 / Risk epidemiologic stratification of the emergent and re-emergent diseases per health areas. Province of Matanzas, 2002-2006

Las enfermedades emergentes y reemergentes constituyen un problema de salud que preocupa a los gobiernos y a las autoridades de salud pública, por los efectos económicos y sociales que pueden ocasionar. Se realizó un estudio observacional descriptivo en la población de la provincia de Matanzas, distribuida geográficamente en sus áreas de salud, con el propósito de estratificar el riesgo para las enfermedades emergentes y reemergentes, en el período 2002-2006. Un grupo de expertos seleccionaron las enfermedades a estudiar y los indicadores, quedando definidos así: para la tuberculosis y el VIH/sida, la tasa de prevalencia y de letalidad; para el dengue y el paludismo, los casos importados y el índice de infestación; para la influenza aviar y la fiebre del Oeste del Nilo Occidental (FNO), el asentamiento de aves migratorias, el arribo de viajeros de áreas endémicas, y también para esta última, el índice de infestación. Los datos fueron obtenidos de las tarjetas de Enfermedades de Declaración Obligatoria y certificados de defunción, de la Dirección Provincial de Salud, del Centro Provincial de Higiene y Epidemiología, del sistema de vigilancia vectorial de la Unidad Provincial de Vectores y de aves migratorias de la Dirección Provincial de Medicina Veterinaria y el Ministerio de Ciencia Tecnología y Medio Ambiente (CITMA). Se obtuvo como resultado que Playa, Varadero, Agramante y Jagüey Grande fueron las áreas de salud de mayor riesgo, lo que es de vital importancia para los cuadros a diferentes niveles del sistema, ya que posibilita con una base científica la reorientación de la vigilancia, la organizar los servicios de salud e intervención oportuna.

The emergent and re-emergent diseases are a health problem worrying governments and public health authorities because of the economic and social effects they can produce. We carried out a descriptive observational study in the population of the province of Matanzas, geographically distributed in their health area, with the purpose of stratifying the risk for the emergent and re-emergent diseases, in the period 2002-2006. A group of experts selected the diseases to study and the indicators, being defined this way: for the tuberculosis and HIV/AIDS, the prevalence rate and the lethality; for dengue and malaria, the imported cases and the infestation index; for the avian flu and the West Nile fever, the migratory birds settlement and the traveler arrival from the endemic areas, and for the last one also the infestation rate. The data were collected from the cards of Obligatory Declaration Diseases and the decease certifications, from the Provincial Direction of Health, the Provincial Center of Hygiene and Epidemiology, the vectorial surveillance system of the Provincial Unit of Vectors, the Provincial Center of Veterinary Medicine, and the Ministry of Sciences, Technology and Environment. As a result we obtained that Playa, Varadero, Agramonte and Jagüey Grande were the health areas at higher risk. This is of great importance for the executives at the different levels of the system, making possible the reorientation of the surveillance, the organization of the health services and te opportune intervention on a scientific basis.

Estratificación epidemiológica del riesgo de las enfermedades emergentes y reemergentes por municipios, Matanzas, 2002-2006 / Epidemiologic stratification of the emergent and re-emergent diseases risk per municipalities, Matanzas, 2002-2006

Las enfermedades emergentes y reemergentes constituyen un problema de salud que preocupa a los gobiernos y a las autoridades de Salud Pública por los efectos económicos y sociales que pueden ocasionar. Se realizó un estudio observacional descriptivo en la población de la provincia de Matanzas, distribuida geográficamente en sus municipios, para estratificar el riesgo para las enfermedades emergentes y reemergentes en el período 2002-2006. Se seleccionaron las enfermedades a estudiar y los indicadores por un grupo de expertos: para la tuberculosis y el VIH/sida fueron la tasa de prevalencia y de letalidad, para el dengue y el paludismo los casos importados y el índice de infestación, para la influenza aviar y la fiebre del Oeste del Nilo Occidental el asentamiento de aves migratorias, el arribo de viajeros de áreas endémicas y para esta última también el índice de infestación. Los datos fueron obtenidos de las tarjetas de enfermedades de declaración obligatoria y certificados de defunción de la Dirección Provincial de Salud y del Centro Provincial de Higiene, Epidemiología y Microbiología, así como del sistema de vigilancia vectorial de la Unidad Provincial de Vectores y de aves migratorias de la Dirección Provincial de Medicina Veterinaria y el CITMA. Obteniéndose como resultado que Jagüey Grande, Matanzas y Varadero fueron los municipios de mayor riesgo, constituyendo una herramienta de trabajo para los cuadros a diferentes niveles del sistema, ya que brinda un grupo de elementos con base científica para reorientar la vigilancia de estas enfermedades, organizar los servicios de salud e intervenir oportunamente.

The emergent and re-emergent diseases are a health problem worrying the governments and the public health authorities because of the economic and social effects they can have. We carried out an observational descriptive study in the population of the province of Matanzas, geographically distributed in municipalities, to stratify the risk of the emergent and re-emergent diseases in the period 2002-2006. We selected the diseases and the indicators to study for a group of experts: for the tuberculosis and HIV/AIDS were choose the indicators prevalence rate and lethality; for the dengue and malaria, the imported cases and the infestation index; for the chicken influenza and the Western Nile fever, the population of the migratory birds, the arrival of passengers from endemic areas, and for the last one the infestation index. The data were obtained from the forms of the diseases of obligatory declaration and from the decease certificates in the Provincial Health Direction and the Provincial Center of Hygiene, Epidemiology and Microbiology, and also from the system of vectorial surveillance of the Provincial Unit of Vectors. The data about the migratory birds were gathered in the Provincial Directions of Veterinary Medicine and of Sciences, Technology and Environment. The municipalities of Jagüey Grande, Matanzas and Varadero were the ones with the highest risks. This is a working tool for the persons in charge in the different levels of the system giving elements on a scientific basement to re-orientate the surveillance of these diseases, organize the health care services and the intervention on time.

Influenza A: [revisión] / Influenza A: [review]

La influenza es una enfermedad viral aguda que afecta una gran parte de la población mundial cada año. Es producida por los virus de la influenza, los cuales pertenecen a la familia Orthomyxoviridae. Se conocen tres tipos: A, B y C; los virus tipo A afectan una gran variedad de especies animales, incluyendo la humana, en tanto que los tipos B y C usualmente se limitan al hombre, aunque se han aislado de focas y cerdos, respectivamente...

Experimental infection of chickens, ducks and quails with the highly pathogenic H5N1 avian influenza virus

Highly pathogenic avian influenza viruses (HPAIV) of the H5N1 subtype have spread since 2003 in poultry and wild birds in Asia, Europe and Africa. In Korea, the highly pathogenic H5N1 avian influenza outbreaks took place in 2003/2004, 2006/2007 and 2008. As the 2006/2007 isolates differ phylogenetically from the 2003/2004 isolates, we assessed the clinical responses of chickens, ducks and quails to intranasal inoculation of the 2006/2007 index case virus, A/chicken/Korea/IS/06. All the chickens and quails died on 3 days and 3-6 days post-inoculation (DPI), respectively, whilst the ducks only showed signs of mild depression. The uninoculated chickens and quails placed soon after with the inoculated flock died on 5.3 and 7.5 DPI, respectively. Both oropharyngeal and cloacal swabs were taken for all three species during various time intervals after inoculation. It was found that oropharyngeal swabs showed higher viral titers than in cloacal swabs applicable to all three avian species. The chickens and quails shed the virus until they died (up to 3 to 6 days after inoculation, respectively) whilst the ducks shed the virus on 2-4 DPI. The postmortem tissues collected from the chickens and quails on day 3 and days 4-5 and from clinically normal ducks that were euthanized on day 4 contained the virus. However, the ducks had significantly lower viral titers than the chickens or quails. Thus, the three avian species varied significantly in their clinical signs, mortality, tissue virus titers, and duration of virus shedding. Our observations suggest that duck and quail farms should be monitored particularly closely for the presence of HPAIV so that further virus transmission to other avian or mammalian hosts can be prevented.

Influenza aviar y riesgo de pandemia / Pandemic risk of avian influenza

Influenza is a common season pathology that occasionally presents pandemia, caused by a new Influenza A virus subtype that results from the genomic recombination of human virus with virus from other species. During the last years, there is a worldwide alert situation in terms of a new pandemia, due to the existence of Influenza A virus subtype H5N1 in birds from Southeast Asia, Europe and Africa. There are some sporadic cases in humans produced by close exposure with infected birds. The present article reviews the virologic characteristics of Influenza A H5N1 virus in humans and the chilean guidelines for a potential pandemia. Influenza is a respiratory disease produced by Influenza virus A,B,C, being the A type the most important due to its capacity to change structure and cause epidemia or pandemia. The last pandemias were classified as Spamsh flu in 1918-1919 (H1N1), Asian flu in 1957 (H2N2) and the Hong-Kong flu in 1967 (H3N2), with the biggest death population in 1918. In template countries, Influenza presents in epidemia affecting the winter months; in tropical countries, the virus circulation occurs during the whole year.

Influenza es una enfermedad común que se presenta en Chile en forma estacional. Ocasionalmente ocurren pandemias las que se generan cuando aparece un nuevo subtipo de virus influenza A en la humanidad producto de la recombinación de genomas de virus de influenza humano con virus de influenza de otras especies. En los últimos años la humanidad se encuentra en una situación de alerta de una nueva pandemia dada la existencia de la más grande epizootia por influenza A, subtipo H5N1 en aves que se extiende desde el Sudeste Asiático a Europa Oriental, Occidental y África. Se han documentado casos esporádicos en humanos por contacto cercano con aves infectadas. El presente artículo revisa las características virológicas del virus de influenza A, la situación actual de la epizootia por H5N1, las características de esta infección en humanos y el estado de preparación que se encuentra Chile frente a una eventual pandemia.

Leucocyte and lymphocyte count in cases of bird flu infection in Thailand.

Bird flu or avian flu is a new emerging Infectious disease. The H5N1 virus has not only affected the fowls but also the human beings. Severe disease with high mortality in humans in Vietnam and Thailand are reported. This mini-study was undertaken in order to document the Impact of bird flu infection on leucocyte and lymphocyte counts among patients of Thailand. This study was designed as a descriptive retrospective study. A literature review on the papers concerning human bird flu in Thailand was performed. According to this study, there are 6 cases covering 12 Thai patients with confirmed diagnosis of bird flu. However, the complete data were available on only 6 patients. The reported leucocyte count ranges from 1,200 cells/cmm to 5,680 cells/cmm and the lymphocyte count ranges from 454 cells/ cmm to 1,440 cells/cmm. The average leucocyte and lymphocyte counts equalled to 3,230.0 +/- 1,552.7 cells/cmm and 748.7 +/- 348.5 cells/cmm, respectively. According to this study, low lymphocyte count is common. This can support the previous observation for the lymphocyte suppression effect of H5N1 virus.