H1N1 Swine Flu Update
H1N1 Update from the CDC
The CDC reports that flu activity in the United States is declining and is low nationally. Most flu continues to be due to 2009 H1N1. The most up to date information on flu activity is published weekly from October through mid-May in the FluView report, available at http://www.cdc.gov/flu/weekly/fluactivity.htm or see http://www.cdc.gov/h1n1flu/update.htm for a summary of the weekly domestic update.
Recent 2009 H1N1 viruses remain similar to the virus chosen for the 2009 H1N1 vaccine, and remain susceptible to the antiviral drugs oseltamivir and zanamivir with rare exception. In nearly all countries of the world where influenza virus infections have been reported, the 2009 H1N1 virus continues to predominate among all subtyped influenza A viruses.
Flu activity, caused by either 2009 H1N1 or seasonal flu viruses, may rise and fall, but is expected to continue for several more weeks.
There are still uncertainties surrounding the rest of this flu season, including the possibility of the circulation of seasonal influenza viruses and ongoing circulation of 2009 H1N1 viruses.
CDC estimates that between 42 million and 86 million 2009 H1N1 cases occurred between April 2009 and February 13, 2010. The mid-level in this range is about 59 million people infected with 2009 H1N1. A large number of people in the United States are likely to have antibody or immunity against 2009 H1N1 from vaccination and/or infection with 2009 H1N1.
However, with a population of more than 300 million in this country, a substantial number of people likely remain susceptible to 2009 H1N1, which continues to circulate at this time.
Current CDC Recommendations
- Though flu activity has declined since the late fall, there are still uncertainties surrounding the rest of this flu season, including the possibility of the circulation of seasonal influenza viruses and ongoing circulation of 2009 H1N1 viruses through the spring months. In addition, sporadic cases of influenza may also be detected in the summer.
- CDC continues to encourage people to get vaccinated throughout the flu season. It is important that providers continue to encourage vaccination, especially for those with high risk conditions.
- The age group with the highest rate of 2009 H1N1 deaths has been people 50–64 years of age; 80 percent of whom have had an underlying health condition. However, the age group with the highest rate of hospitalization is children less than 5 years of age.
- Health conditions that increase the risk of being hospitalized from 2009 H1N1 include lung disease like asthma or chronic pulmonary disease (COPD), diabetes, heart disease, and neurologic disease and pregnancy.
- In addition, minority populations have been harder-hit by the 2009 H1N1 pandemic than non-minority groups.
- There also is growing evidence to support early concerns that people who are morbidly obese are at greater risk of serious 2009 H1N1 complications.
CDC also is encouraging people 65 years and older to get vaccinated against 2009 H1N1. Although less likely to get sick with 2009 H1N1 than younger people, people 65 and older are at higher risk of serious complications if they do get sick.
In addition, parents are encouraged to ensure that children younger than 10 years old get both doses of 2009 H1N1 vaccine. The recommended interval between the first and second dose is 28 days.
It remains very important that antiviral drugs be used early to treat flu in people who are very sick (e.g., people who are in the hospital) and people who are sick with flu and have a greater chance of getting serious flu complications, such as people with asthma, diabetes, heart disease or neurologic disease, children younger than 2 years, women who are pregnant, or people who are 65 and older.
CDC recommends that health departments, providers and pharmacies retain their unexpired 2009 H1N1 vaccine supplies as a reserve, should demand for vaccination increase before seasonal vaccine becomes available. 2009 H1N1 virus is still circulating and continues to cause illness, hospitalizations, and death.
2009 H1N1 and Travel
Pandemic 2009 H1N1 influenza viruses are expected to continue to circulate throughout 2010, including during the typical Southern Hemisphere influenza season.
Any traveler who wants to reduce the risk for pandemic 2009 H1N1 influenza infection should get vaccinated with the influenza A (H1N1) 2009 monovalent vaccine, preferably at least 2 weeks before departure.
The influenza A (H1N1) 2009 monovalent vaccine is widely available in the United States.
The vaccine strain in the influenza A (H1N1) 2009 monovalent vaccine (also called H1N1 vaccine or pandemic vaccine) is the same strain that was recommended by the World Health Organization for use in the Southern Hemisphere 2010 seasonal vaccine. The Southern Hemisphere influenza season starts in April or May.
In addition, with the soccer World Cup taking place in June in South Africa during the Southern Hemisphere influenza season, it's possible that 2009 H1N1 viruses may circulate during that time.
Travelers who have already received the 2009 H1N1 vaccine do not need to be revaccinated with the 2009 H1N1 monovalent vaccine.