الفهرس 
History of InfluenzaOnly 14 pages are availabe for public view
 |  | from | 76 |  |  |
| | | from | 76 | | |
Abstract
Historically, influenza has caused outbreaks of respiratory illness for centuries, including three pandemics in the 20th century. There are three types of influenza viruses: types A, B, and C. Only type A influenza viruses cause pandemics. Seasonal influenza outbreaks can be caused by either type A or type B influenza viruses. Influenza type C viruses cause mild illness in humans but do not cause epidemics or pandemics.
Typical clinical manifestations of pandemic H1N1 influenza A infection include fever, headache, cough, sore throat, myalgias, chills, and fatigue; vomiting and diarrhea have also been common, both of which are unusual features of seasonal influenza. Disease severity can range from mild influenza-like illness to multiorgan failure with severe hypoxemia. Individuals with certain medical conditions, those at the extremes of age, and pregnant women are at increased risk of influenza complications, including respiratory failure.
Current predictions estimate that, during a pandemic wave, 12–30% of the population will develop clinical influenza (compared with 5–15% for seasonal influenza) with 4% of those patients requiring hospital admissions and one in five requiring critical care. These patients rapidly develop severe progressive respiratory failure which is often associated with failure of other organs.
In late March and early April 2009, an outbreak of H1N1 influenza A virus infection was detected in Mexico, with subsequent cases observed in many other countries including the United States. On June 11, 2009, the World Health Organization raised its pandemic alert level to the highest level, phase 6, indicating widespread community transmission on at least two continents .
The following measures should be undertaken to prevent the spread of influenza viruses in healthcare settings:
• Administer the pandemic H1N1 and seasonal influenza vaccines to healthcare workers and emergency medical services personnel.
• Enforce respiratory hygiene and cough etiquette
• Establish facility access control measures and triage procedures
• Manage visitor access and movement within the facility
• Follow facility procedures for transport and movement of patients who are on isolation precautions
• Limit the number of healthcare personnel entering an isolation room
• Apply isolation precautions
Real-time reverse transcriptase (rRT)-PCR is the most sensitive and specific test for the diagnosis of pandemic H1N1 influenza A virus infection; however, the test may not be readily available and/or may require several days for processing. Several rapid antigen and immunofluorescent antibody tests are available for the diagnosis of influenza virus infection. However, the sensitivity of these tests varies widely and they do not distinguish between pandemic and seasonal strains of H1N1 influenza A. Confirmation of pandemic H1N1 influenza A infection can only be made by real-time reverse-transcriptase (rRT)-PCR or culture. Most patients with an uncomplicated influenza-like illness who reside in areas where influenza viruses are known to be circulating do not need to be tested for influenza infection. Patients in whom influenza testing should be considered include: a) hospitalized patients with suspected influenza infection b) patients for whom a diagnosis of influenza will affect decisions regarding clinical care, infection control or management of close contacts and c) individuals who died of acute illness in whom influenza was suspected.
Not all individuals with suspected pandemic H1N1 influenza A infection need to be seen by a health care provider or treated. During the current pandemic, patients with mild illness do not need to be tested or treated unless they have risk factors for complications. We recommend prompt initiation of antiviral therapy (with zanamivir or oseltamivir) for individuals with suspected or confirmed influenza infection who are at risk for complicated disease or have severe illness. The duration of therapy with neuraminidase inhibitors is typically five days. Patients with pandemic H1N1 influenza A who develop pneumonia should be treated empirically for community-acquired pneumonia (CAP) .