Epidemiological survey on the benefit of neuraminidase inhibitors on severe acute respiratory syndrome due to COVID-19 / Levantamento epidemiológico do benefício de inibidores de neuraminidase na síndrome respiratória aguda grave por COVID-19 / Encuesta epidemiológica del beneficio de inhibidores de neuraminidase en síndrome respiratorio agudo severo por COVID-19

Background and objectives: The COVID-19 pandemic and its consequent severe acute respiratory syndrome (SARS) have taken the lives of millions since 2020. The use of neuraminidase inhibitors is a promising alternative in treating this disease, with several studies on off-label use being conducted since the beginning of the pandemic, but none of them have a large sample size and analyze multiple risk factors. The purpose of this article is to identify possible associations between various factors and risk of hospitalization, need for ventilation and death, as well as the influence of the prescription of Zanamivir and Oseltamivir on these same indicators. Methods: In this transversal study, approximately 900,000 medical records from all regions of Brazil were collected from the Ministry of Health database, and after that, proper statistical analysis of the variables was performed. Results: Hospitalization was associated with gender, ethnicity, education, local urbanization, State, and its percentage of elderly, as well as the climate. The prescription of Zanamivir and Oseltamivir was associated with higher incidence of symptoms, lower hospitalization and death rate, and lower need for invasive and non-invasive ventilation. Medical records from146,160 patients were excluded due to SARS not caused by COVID-19. Conclusion: From this data, it is possible to draw a risk profile for hospitalization by SARS and consider the use of Zanamivir and Oseltamivir as a treatment for these patients.(AU)

Justificativa e objetivos: A pandemia de COVID-19 e sua consequente síndrome respiratória aguda grave (SRAG) levaram milhões de pessoas a óbito desde 2020. O uso de inibidores da neuraminidase é uma alternativa promissora no tratamento dessa doença, com vários estudos sobre o uso off-label sendo conduzidos desde o início da pandemia, mas nenhum que tenha um grande tamanho amostral e que analise vários fatores de risco. O objetivo deste artigo é identificar possíveis associações entre diversos fatores e risco de hospitalização, necessidade de ventilação e óbito, assim como a influência da prescrição de Zanamivir e Oseltamivir nos mesmos indicadores. Métodos: Neste estudo transversal, foi feito o levantamento de aproximadamente 900 mil prontuários de todas as regiões do Brasil, provenientes de dados do Ministério da Saúde, e em seguida foi realizado o tratamento estatístico adequado das variáveis. Resultados: A hospitalização foi associada a sexo, etnia, escolaridade, urbanização do local, Estado e porcentagem de idosos do mesmo, assim como o clima. Já a prescrição de Zanamivir e Oseltamivir foi associada a maior incidência de sintomas, menor taxa de hospitalização e óbito e menor necessidade de ventilação invasiva e não-invasiva. Foram excluídos 146.160 prontuários devido a SRAG não ocasionada pela COVID-19. Conclusão: Com esses dados, é possível traçar um perfil de risco para hospitalização por SRAG e considerar o uso de Zanamivir e Oseltamivir como tratamento para esses pacientes.(AU)

Justificación y objetivos: la pandemia Covid-19 y su consiguiente síndrome respiratorio agudo severo (SRAS) han muerto millones de personas desde 2020. El uso de inhibidores de la neuraminidasa es una alternativa prometedora en el tratamiento de esta enfermedad, con varios estudios sobre el uso off-label que se realiza desde el principio de la pandemia, pero ninguno que tenga un tamaño de muestra grande y analice múltiples factores de riesgo. El propósito de este artículo es identificar posibles asociaciones entre varios factores y el riesgo de hospitalización, necesidad de ventilación y muerte, así como la influencia de la prescripción de Zanamivir y Oseltamivir en los mismos indicadores. Métodos: En este estudio transversal, se encuestaron a los datos del Ministerio de Salud de aproximadamente 900,000 registros de todas las regiones de Brasil, después de que se realizó un tratamiento estadístico adecuado de las variables. Resultados: La hospitalización se asoció con género, etnia, educación, urbanización del sitio, Estado y porcentaje de ancianos, así como el clima. La prescripción de zanamivir y oseltamivir se asoció con la mayor incidencia de síntomas, menor hospitalización y tasa de mortalidad y menor necesidad de ventilación invasiva y no invasiva. Se excluyeron 146,160 registros médicos debido a SRAS no causado por Covid-19. Conclusión: con estos datos, es posible dibujar un perfil de riesgo para la hospitalización por SRAS y considerar el uso de zanamivir y oseltamivir como tratamiento para estos pacientes.(AU)

Baloxavir treatment of oseltamivir-resistant influenza A/H1pdm09 in two immunocompromised patients.

Few treatment options are available for oseltamivir-resistant influenza. It has been proposed that baloxavir can be effective in this setting due to its distinct mechanism of action but clinical experience is lacking for immunocompromised patients. We report two such cases treated with baloxavir after failure of oseltamivir and detection of oseltamivir resistance mutations. Baloxavir/zanamivir combination therapy was effective in one patient, but persistent viral shedding was noted with baloxavir monotherapy in the other patient.

Efficacy of oseltamivir compared with zanamivir in COPD patients with seasonal influenza virus infection: a randomized controlled trial

Influenza viruses exacerbate chronic obstructive pulmonary disease (COPD) with considerable morbidity and mortality. Zanamivir and oseltamivir are effective in treating influenza. However, their efficacy in relieving influenza symptoms in COPD patients remains unknown, with the lack of controlled trials in this subject. Therefore, we conducted this randomized controlled trial to investigate the clinical efficacy of both interventions in this population. Patients were allocated to two groups (80 patients each): oseltamivir (OSELTA) and zanamivir (ZANA) groups. Oseltamivir (75 mg) was orally administered twice daily for 5 days, while zanamivir (10 mg) was inhaled twice daily for 5 days. Clinical parameters including body temperature, influenza symptoms (i.e., sore throat, cough, etc.), and serial blood tests were recorded on days 1, 3, and 7. We analyzed primary (changes in body temperature) and secondary outcomes (changes in non-specific symptoms) using the pre-protocol and intention-to-treat analyses. Differences between groups were assessed using t-test. Oseltamivir and zanamivir significantly reduced body temperature on the 3rd day after treatment; however, the number of patients who reported clinical improvement in influenza-like symptoms was significantly higher in the OSELTA group compared to the ZANA group on days 3 (85 vs 68.8%, P=0.015) and 7 (97.5 vs 83.8%, P=0.003). However, no significant changes in hematological (white blood cells and its subtypes) and inflammatory (C-reactive protein) parameters were noted (P>0.05). Our results suggested that oseltamivir and zanamivir are effective in reducing body temperature, while oseltamivir led to better clinical improvement regarding influenza-like symptoms in patients with COPD.

A search for medications to treat COVID-19 via in silico molecular docking models of the SARS-CoV-2 spike glycoprotein and 3CL protease.

BACKGROUND: The COVID-19 has now been declared a global pandemic by the World Health Organization. There is an emergent need to search for possible medications. METHOD: Utilization of the available sequence information, homology modeling, and in slico docking a number of available medications might prove to be effective in inhibiting the SARS-CoV-2 two main drug targets, the spike glycoprotein, and the 3CL protease. RESULTS: Several compounds were determined from the in silico docking models that might prove to be effective inhibitors for SARS-CoV-2. Several antiviral medications: Zanamivir, Indinavir, Saquinavir, and Remdesivir show potential as and 3CLPRO main proteinase inhibitors and as a treatment for COVID-19. CONCLUSION: Zanamivir, Indinavir, Saquinavir, and Remdesivir are among the exciting hits on the 3CLPRO main proteinase. It is also exciting to uncover that Flavin Adenine Dinucleotide (FAD) Adeflavin, B2 deficiency medicine, and Coenzyme A, a coenzyme, may also be potentially used for the treatment of SARS-CoV-2 infections. The use of these off-label medications may be beneficial in the treatment of the COVID-19.

Antiviral treatment and virological monitoring of oseltamivir-resistant influenza virus A(H1N1)pdm09 in a patient with chronic B lymphocytic leukemia.

We report the virological monitoring and the antiviral therapy adopted for the treatment of a patient affected by chronic B lymphocytic leukemia, who experienced a severe pneumonia with long-term shedding of influenza virus A(H1N1)pdm09, characterized by an early development of oseltamivir resistance.

Molecular pathway of influenza pan-neuraminidase inhibitor resistance in an immunocompromised patient.

BACKGROUND: Neuraminidase (NA) inhibitors (NAIs), including oseltamivir and zanamivir, play an important therapeutic role against influenza infections in immunocompromised patients. In such settings, however, NAI therapy may lead to the emergence of resistance involving mutations within the influenza surface genes. The aim of this study was to investigate the evolution of NA and haemagglutinin (HA) genes of influenza A(H1N1)pdm09 virus in an immunocompromised patient receiving oseltamivir then zanamivir therapies. METHODS: Nasopharyngeal swab (NPS) samples were collected between 27 January 2018 and 11 April 2018 from a haematopoietic stem cell transplant recipient. These include 10 samples collected either pre-therapy, during oseltamivir and zanamivir treatment as well as after therapy. The A(H1N1)pdm09 HA/NA genes were sequenced. The H275Y NA substitution was quantified by droplet digital RT-PCR assay. A(H1N1)pdm09 recombinant viruses containing HA mutations were tested by HA elution experiments to investigate in vitro binding properties. RESULTS: Oseltamivir rapidly induced the H275Y NA mutation which constituted 98.33% of the viral population after 15 days of oseltamivir treatment. The related HA gene contained S135A and P183S substitutions within the receptor-binding site. After a switch to zanamivir, 275H/Y and 119E/G/D mixed populations were detected. In the last samples, the double H275Y-E119G NA variant dominated with S135A and P183S HA substitutions. CONCLUSIONS: This report confirms that oseltamivir can rapidly induce the emergence of the H275Y substitution in A(H1N1)pdm09 viruses and subsequent switch to zanamivir can lead to additional substitutions at codon E119 resulting in multi-drug resistance. Such data additionally suggest a potential compensatory role for HA substitutions near the receptor binding site.

Characteristics and mortality of severe influenza cases treated with parenteral aqueous zanamivir, United Kingdom, October 2009 to January 2011.

BACKGROUND: Aqueous zanamivir solution, an investigational product, was provided by the manufacturer on compassionate grounds for parenteral administration to severe H1N1pdm09 influenza cases during the 2009 pandemic. OBJECTIVE: To describe characteristics and outcomes of UK patients receiving parenteral zanamivir therapy. METHODS: Collaborators at multiple hospital sites gathered retrospective data on patients receiving aqueous zanamivir therapy between Q4 2009 and Q1 2011. We present analysis of the demographics, clinical features, treatment and outcomes of this cohort. RESULTS: Data on 185 cases were obtained (response rate of 38%; median age 43 years; 62% male; 17% non-Caucasian ethnic group). Most frequent co-morbidities included cancer, immunosuppression and respiratory conditions. Most patients received intravenous zanamivir alone (90%), for durations of up to 21 days. 13% of cases had adverse effects related to zanamivir therapy. Thirty four percentage of cases died. No significant relationship was seen between mortality and timing or route of administration of aqueous zanamivir therapy. CONCLUSIONS: The response rate of this observational study of the outcomes of treatment of severe influenza was low, allowing limited conclusions to be drawn. Some potential adverse effects were noted. Clinicians should carefully consider potential risks and benefits of use of this product. New treatment options are urgently required to improve outcomes for patients with severe influenza infections.

Antiviral therapy for respiratory viral infections in immunocompromised patients.

INTRODUCTION: Respiratory viruses (influenza, parainfluenza, respiratory syncytial virus, coronavirus, human metapneumovirus, and rhinovirus) represent the most common causes of respiratory viral infections in immunocompromised patients. Also, these infections may be more severe in immunocompromised patients than in the general population. Early diagnosis and treatment of viral infections continue to be of paramount importance in immunocompromised patients; because once viral replication and invasive infections are evident, prognosis can be grave. Areas covered: The purpose of this review is to provide an overview of the main antiviral agents used for the treatment of respiratory viral infections in immunocompromised patients and review of the new agents in the pipeline. Expert commentary: Over the past decade, important diagnostic advances, specifically, the use of rapid molecular testing has helped close the gap between clinical scenarios and pathogen identification and enhanced early diagnosis of viral infections and understanding of the role of prolonged shedding and viral loads. Advancements in novel antiviral therapeutics with high resistance thresholds and effective immunization for preventable infections in immunocompromised patients are needed.

Abordaje diagnostico terapéutico de la neumonía viral grave / Diagnostic therapeutic approach to severe viral pneumonia

La guía de referencia rápida tiene como objetivo proporcionar al usuario las recomendaciones clave de la guía. Abordaje diagnóstico y terapéutico de la neumonía viral grave, seleccionadas con base a su impacto en salud por el grupo desarrollador, las cuales pueden variar en función de la intervención de que se trate, así como del contexto regional o local en el ámbito de su aplicación.

Within-Host Models of High and Low Pathogenic Influenza Virus Infections: The Role of Macrophages.

The World Health Organization identifies influenza as a major public health problem. While the strains commonly circulating in humans usually do not cause severe pathogenicity in healthy adults, some strains that have infected humans, such as H5N1, can cause high morbidity and mortality. Based on the severity of the disease, influenza viruses are sometimes categorized as either being highly pathogenic (HP) or having low pathogenicity (LP). The reasons why some strains are LP and others HP are not fully understood. While there are likely multiple mechanisms of interaction between the virus and the immune response that determine LP versus HP outcomes, we focus here on one component, namely macrophages (MP). There is some evidence that MP may both help fight the infection and become productively infected with HP influenza viruses. We developed mathematical models for influenza infections which explicitly included the dynamics and action of MP. We fit these models to viral load and macrophage count data from experimental infections of mice with LP and HP strains. Our results suggest that MP may not only help fight an influenza infection but may contribute to virus production in infections with HP viruses. We also explored the impact of combination therapies with antivirals and anti-inflammatory drugs on HP infections. Our study suggests a possible mechanism of MP in determining HP versus LP outcomes, and how different interventions might affect infection dynamics.

Influenza A H1N1 pdm09-associated myocarditis during zanamivir therapy.

A 9-year-old girl developed influenza A H1N1 pdm09-associated myocarditis and pericarditis 2 days after starting zanamivir therapy. The virus was detected in the respiratory tract but not in the serum or pericardial effusion. The virus sampled from the respiratory tract had normal susceptibility to neuraminidase inhibitors. Although no differences in interferon-γ, interleukin (IL)-1ß, and tumor necrosis factor-α were observed between the plasma and pericardial effusion, some inflammatory cytokines or chemokines (IL-6 and IL-8) and vascular endothelial growth factor were remarkably elevated in the pericardial effusion compared with the plasma. This suggested that the influenza virus, after infecting the respiratory tract, affected the myocardium, causing myocarditis to gradually develop, which might have been followed by an autoreactive pericarditis causing increased pericardial effusion. Therefore, influenza-associated myocarditis should be considered when influenza patients have respiratory and cardiac involvement, even during treatment with a neuraminidase inhibitor.

Primarily oseltamivir-resistant influenza A (H1N1pdm09) virus evolving into a multidrug-resistant virus carrying H275Y and I223R neuraminidase substitutions.

Antiviral susceptibility testing and reporting of viruses carrying amino acid substitutions conferring antiviral drug resistance is essential to assess the spread and clinical impact of these viruses. Here, we report on a patient who was infected with a primarily oseltamivir-resistant influenza A (H1N1pdm09) virus following allogeneic stem cell transplantation and rituximab treatment. Under prolonged virus replication and zanamivir therapy the neuraminidase amino acid substitutions H275Y and I223R were detected conferring high-level resistance to oseltamivir and cross-resistance to zanamivir. The emergence of these amino acid changes has been reported rarely worldwide and has been associated with fatal clinical outcomes. The patient survived the influenza infection after 170 days of follow-up.

Multiple influenza A (H3N2) mutations conferring resistance to neuraminidase inhibitors in a bone marrow transplant recipient.

Immunocompromised patients are predisposed to infections caused by influenza virus. Influenza virus may produce considerable morbidity, including protracted illness and prolonged viral shedding in these patients, thus prompting higher doses and prolonged courses of antiviral therapy. This approach may promote the emergence of resistant strains. Characterization of neuraminidase (NA) inhibitor (NAI)-resistant strains of influenza A virus is essential for documenting causes of resistance. In this study, using quantitative real-time PCR along with conventional Sanger sequencing, we identified an NAI-resistant strain of influenza A (H3N2) virus in an immunocompromised patient. In-depth analysis by deep gene sequencing revealed that various known markers of antiviral resistance, including transient R292K and Q136K substitutions and a sustained E119K (N2 numbering) substitution in the NA protein emerged during prolonged antiviral therapy. In addition, a combination of a 4-amino-acid deletion at residues 245 to 248 (Δ245-248) accompanied by the E119V substitution occurred, causing resistance to or reduced inhibition by NAIs (oseltamivir, zanamivir, and peramivir). Resistant variants within a pool of viral quasispecies arose during combined antiviral treatment. More research is needed to understand the interplay of drug resistance mutations, viral fitness, and transmission.

Y155H amino acid substitution in influenza A(H1N1)pdm09 viruses does not confer a phenotype of reduced susceptibility to neuraminidase inhibitors.

The Y155H amino acid substitution in the neuraminidase gene (NA) has previously been associated with highly reduced inhibition by neuraminidase inhibitors in the seasonal H1N1 influenza A virus which circulated in humans before the 2009 pandemic. During the 2012/13 epidemic season in Spain, two A(H1N1) pdm09 viruses bearing the specific Y155H substitution in the NA were detected and isolated from two patients diagnosed with severe respiratory syndrome and pneumonia requiring admission to the intensive care unit. Contrary to what was observed in the seasonal A(H1N1) viruses, neither of the Y155H A(H1N1) pdm09 viruses described here showed a phenotype of reduced inhibition by NAIs as determined by the neuraminidase enzyme inhibition assay (MUNANA). High-throughput sequencing of the NA of both Y155H viruses showed that they were composed to >99% of H155 variants. We believe that this report can contribute to a better understanding of the biological significance of amino acid substitutions in the neuraminidase protein with regard to susceptibility of influenza viruses to neuraminidase inhibitors. This is of critical importance for optimal management of influenza disease patients.

Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children

BACKGROUND: Neuraminidase inhibitors (NIs) are stockpiled and recommended by public health agencies for treating and preventing seasonal and pandemic influenza. They are used clinically worldwide. OBJECTIVE: To describe the potential benefits and harms of NIs for influenza in all age groups by reviewing all clinical study reports of published and unpublished randomised, placebo-controlled trials and regulatory comments. METHODS Search methods: We searched trial registries, electronic databases (to 22 July 2013) and regulatory archives, and corresponded with manufacturers to identify all trials. We also requested clinical study reports. We focused on the primary data sources of manufacturers but we checked that there were no published randomised controlled trials (RCTs) from non-manufacturer sources by running electronic searches in the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, MEDLINE (Ovid), EMBASE, Embase.com, PubMed (not MEDLINE), the Database of Reviews of Effects, the NHS Economic Evaluation Database and the Health Economic Evaluations Database. Selection criteria: Randomised, placebo-controlled trials on adults and children with confirmed or suspected exposure to naturally occurring influenza. Data collection and analysis: We extracted clinical study reports and assessed risk of bias using purpose-built instruments. We analysed the effects of zanamivir and oseltamivir on time to first alleviation of symptoms, influenza outcomes, complications, hospitalisations and adverse events in the intention-to-treat (ITT) population. All trials were sponsored by the manufacturers. MAIN RESULTS: We obtained 107 clinical study reports from the European Medicines Agency (EMA), GlaxoSmithKline and Roche. We accessed comments by the US Food and Drug Administration (FDA), EMA and Japanese regulator. We included 53 trials in Stage 1 (a judgement of appropriate study design) and 46 in Stage ...

Predictors of fatality in pandemic influenza A (H1N1) virus infection among adults.

BACKGROUND: The fatality attributed to pandemic influenza A H1N1 was not clear in the literature. We described the predictors for fatality related to pandemic influenza A H1N1 infection among hospitalized adult patients. METHODS: This is a multicenter study performed during the pandemic influenza A H1N1 [A(H1N1)pdm09] outbreak which occurred in 2009 and 2010. Analysis was performed among laboratory confirmed patients. Multivariate analysis was performed for the predictors of fatality. RESULTS: In the second wave of the pandemic, 848 adult patients were hospitalized because of suspected influenza, 45 out of 848 (5.3%) died, with 75% of fatalities occurring within the first 2 weeks of hospitalization. Among the 241 laboratory confirmed A(H1N1)pdm09 patients, the case fatality rate was 9%. In a multivariate logistic regression model that was performed for the fatalities within 14 days after admission, early use of neuraminidase inhibitors was found to be protective (Odds ratio: 0.17, confidence interval: 0.03-0.77, p=0.022), nosocomial infections (OR: 5.7, CI: 1.84-18, p=0.013), presence of malignant disease (OR: 3.8, CI: 0.66-22.01, p=0.133) significantly increased the likelihood of fatality. CONCLUSIONS: Early detection of the infection, allowing opportunity for the early use of neuraminidase inhibitors, was found to be important for prevention of fatality. Nosocomial bacterial infections and underlying malignant diseases increased the rate of fatality.

European guidelines for prevention and management of influenza in hematopoietic stem cell transplantation and leukemia patients: summary of ECIL-4 (2011), on behalf of ECIL, a joint venture of EBMT, EORTC, ICHS, and ELN.

Influenza may cause severe disease and mortality in leukemia patients and in hematopoietic stem cell transplantation recipients. The 4th European Conference of Infections in Leukemia (ECIL-4) has developed evidence-based guidelines for prevention and management of influenza infections in these patients. Real-time reverse-transcription polymerase chain reaction is the diagnostic test of choice, as it is the most sensitive and specific test for influenza. The risks for severe influenza and fatal outcome include lymphopenia, older age, influenza soon after transplantation or chemotherapy, steroid treatment, and lack of early antiviral therapy. Neuraminidase inhibitors (oral oseltamivir or inhalation of zanamivir) are currently the most effective therapeutic agents for influenza. Main preventive measures include annual vaccination of patients, household contacts, and hospital staff. This review summarizes ECIL-4's main recommendations.

Efficient control of pandemic 2009 H1N1 virus infection with intravenous zanamivir despite the lack of immune function.

A teenager who acquired 2009 H1N1 influenza A lower respiratory tract infection during total bone marrow and lymphoid aplasia, in the setting of human leukocyte antigen-haploidentical hematopoietic stem cell transplantation, was successfully treated with intravenous zanamivir. This case demonstrates efficient control of pandemic influenza infection by intravenous zanamivir in the absence of any functional immune system, thus suggesting profound antiviral activity.

Birth outcomes among women exposed to neuraminidase inhibitors during pregnancy.

PURPOSE: To compare birth outcomes between women exposed and unexposed to the antiviral medications oseltamivir or zanamivir during pregnancy. METHODS: This was an observational cohort study including women who gave birth to singletons in Sweden 2005-2007 and their infants. We obtained information from the national health registers and evaluated risks of low Apgar score, small for gestational age (SGA), low birth weight, preterm delivery, congenital malformations, birth-related death (stillbirth and neonatal death combined), and neonatal morbidity by conditional logistic regression. The unexposed [n = 860] were matched to the exposed [n = 86] by birth year and fetal gender. RESULTS: A total of 81 women filled a prescription with oseltamivir only, 2 with zanamivir, and 3 with both oseltamivir and zanamivir. Compared with the unexposed infants, the exposed ones had higher risks of late transient hypoglycemia (crude OR = 4.00, 95%CI: 1.26-12.76). There were no statistical increased risks of low Apgar score, congenital malformations, SGA, low birth weight, preterm birth, or birth-related death. Adjusting for maternal age, parity, smoking, and body mass index had minor effects on the results. None of the women exposed to oseltamivir or zanamivir had been admitted to hospital for influenza during their pregnancy. CONCLUSIONS: Except for an increased risk of late transient hypoglycemia, we found no increased risks of adverse birth outcomes among infants exposed to neuraminidase inhibitors in fetal life compared with the unexposed.

[Clinical features and contagiousness of influenza A(H1N1) in health care workers and hospitalized patients in a Mexico City hospital]. / Características y contagiosidad de influenza A(H1N1) y estacional en trabajadores sanitarios y pacientes de un hospital en la ciudad de México.

INTRODUCTION: Respiratory infections increased in Mexico in 2009 due to an epidemic of influenza. METHODS: To compare symptoms and infectivity of influenza A(H1N1) and seasonal influenza we evaluated epidemiological data and microbiological sampling of health workers (HW) and patients who probably had influenza. RESULTS: From April to November 2009 we studied 83 HW (29 with influenza A(H1N1) and 8 with seasonal influenza) and 71 patients (26 and 11, respectively). The subtypes of influenza had similar clinical data. CONCLUSIONS: Fifteen patients with immunosuppression or chronic diseases developed fatal pneumonia; the infectivity was greater for influenza A(H1N1).