A study to characterize children and adults with influenza like symptoms and to determine risk factors for severe disease and death among those with H1N1.

In March 2009, a new influenza A virus, novel H1N1 (commonly referred to as "swine flu"), began causing an increase in reports of influenza-like illness in North America. Although the virus subsequently spread rapidly around the world, the earliest reported outbreak of cases occurred in Mexico City, which is seen as the epicenter of the influenza pandemic, the world's first in 40 years.

Many questions remain about this emerging pandemic and the virus causing it, the answers to which could better inform patient management and policy decisions both in Mexico and internationally. Sparse reliable clinical research data have been collected on the natural history of the disease, on the risk factors associated with severe disease, or on the severity of this pandemic influenza as compared to seasonal influenzas. This study is an initial step to better characterize individuals in Mexico who develop influenza-like illness (including illness caused by novel H1N1), to describe the clinical management of those individuals, and to assess their short-term outcome. The planned data collection will provide timely information to inform policy and guidelines for the local populations and governments involved and may also be used to design future ancillary studies of this influenza virus and/or studies of other emerging infectious diseases.

The purpose of this observational study is to characterize individuals in Mexico who seek medical care for influenza-like illness (ILI) and to describe clinical course over a period of at least 28 days after enrollment.

Inclusion Criteria:

• Signed informed consent by participant, or for pediatric participants, signed informed consent by parent/legal guardian and, where appropriate, signed assent by participant
• At least one respiratory symptom (e.g., shortness of breath, postnasal drip, cough) and
• One of the following criteria:
• Fever (≥ 38 °C by any method: oral, axillary, etc.) on examination or participant-reported fever (≥ 38° C) or feverishness in the past 24 hours
• One or more non-respiratory symptoms (e.g., malaise, headache, myalgia,chest pain)
• Consenting to provide aspirate or naso-pharyngeal swab

Exclusion Criteria

• The onset of illness is more than 48 hours after hospitalization.
• Participants previously included in this study within the last 30 days.

Patients with influenza-like illness presenting to clinical sites in Mexico