Published Date: 2012-12-31 10:28:20
Subject: PRO/EDR> Influenza (116): (USA) early start
Archive Number: 20121231.1476318
INFLUENZA - (116): (USA), EARLY START
A ProMED-mail posthttp://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseaseshttp://www.isid.org
Date: Sat 29 Dec 2012
Source: The Washington Post, Associated Press report [edited]http://www.washingtonpost.com/national/ ... _headlines
The flu season in the United States is having its earliest start in nearly a decade, and health officials say this season [2012-2013] could be a bad one. Although flu is always unpredictable, the early nature of the cases and the predominant type circulating this year  could make this a severe flu season, said officials at the Centers for Disease Control and Prevention [CDC]. But officials said the vaccine formulated for this year is well-matched to the strains of the virus seen so far and urged those who have not been vaccinated to get a flu shot.
In early December 2012, the CDC said it was noticing an increase in flu activity about a month before authorities normally see it, and the earliest since the 2003-2004 flu season. The primary strain this season is H3N2, an influenza A virus that has been associated in the past with more severe flu seasons.
Since the beginning of December , "there has been increasing influenza activity in more parts of the United States and more cases of flu," said Joe Bresee, chief of epidemiology at CDC's influenza division, in an interview last week. "We have seen increasing trends that flu is increasing in the last few weeks of the year, and I wouldn't be surprised if we see that continue into the new year." Influenza often peaks in January, February or even later.
Reports of flu have been reported in 29 states, including Maryland and Virginia. As of 15 Dec 2012, higher-than-normal reports of flu-like illnesses had been reported in 12 states, most of them in the South and Southeast. They are: Virginia, Alabama, Georgia, Louisiana, Mississippi, Missouri, North and South Carolina, Tennessee, Texas, Illinois and Utah.
Based on data from the past 2 decades, during the years when H3N2 is the predominant flu strain, "there are more deaths and hospitalizations," Bresee said. It is not completely clear why. One factor may be that the elderly, who are at high risk for flu complications, tend to become sicker with the H3N2 strain than the other 2 common flu strains, he said.
But this flu season offers 2 bits of good news as well. Of the flu strains that are spreading this year , about 80 percent are the influenza A type, and almost all of those are the H3N2 strain, Bresee said. That matches well with this year's flu vaccine, which includes the H3N2 strain. Flu vaccines are designed to protect against 3 influenza viruses that experts predict will be the most common during the upcoming season. The 3 kinds of influenza viruses that commonly circulate among people today are influenza B, influenza A (H1N1), and influenza A (H3N2). Each year, one flu virus of each kind is used to produce seasonal influenza vaccine.
Also, the Food and Drug Administration on 21 Dec 2012 expanded the approved use of Tamiflu [a neuraminidase inhibitor] to treat children as young as 2 weeks old who have shown symptoms of flu. The drug was previously approved to treat adults and children one year and older. The dose for children under one year old must be based on their exact weight.
Flu is extremely unpredictable. "You never know when the peak will occur or how big the peak will be," Bresee said. "If you've seen one flu year, it's just one flu year." Last winter's flu season [2011-2012], for example, set a new record for the lowest and shortest peak of influenza-like illness. The season began late and was mild compared with most previous seasons. The last time a regular flu season started this early was the winter of 2003-04, which proved to be one of the deadliest seasons in the past 35 years, with more than 48 000 deaths. The dominant type of flu back then was the same one seen this year . But experts said there is a critical difference between then and now: In 2003-04, the vaccine was poorly matched to the predominant flu strain. Also, health officials said more vaccine is available now, and vaccination rates have risen for the general public and for key groups such as children, pregnant women and health-care workers.
About 112 million Americans had been vaccinated by the end of November 2012, the CDC said. Manufacturers were expecting to produce about 135 million total doses this year . Flu vaccinations are recommended for everyone 6 months or older. On average, about 25 000 Americans die each flu season, according to the CDC.
Flu usually peaks in midwinter. Symptoms can include fever, cough, runny nose, head and body aches, and fatigue. Some people also suffer vomiting and diarrhea, and some develop pneumonia or other severe complications. A strain of swine flu that hit in 2009 caused a wave of cases in the spring and then again in the early fall. But that was considered a unique type of flu, distinct from the conventional strains that circulate every year, experts said.
[Byline: Jacquelyn Martin]
[There are distinctive differences in the characteristics of the early phase of the northern hemisphere winter influenza epidemic between North America and the European Region. In particular. Influenza A/(H3N2) virus is not the predominant virus in the European Region.
According to the current EuroFlu - Weekly Electronic Bulletin (Week 5: 17/12/2012-23/12/2012, 28 Dec 2012, Issue N 468 http://www.euroflu.org/cgi-files/bulletin_v2.cgi
): "Influenza activity is slowly increasing with more countries in different parts of the [European] Region reporting sporadic co-circulation of influenza A(H1N1)pdm09, A(H3N2) and type B viruses. This week, the reporting of influenza surveillance data is incomplete due to the Christmas holidays. This is reflected in the lower number of tests performed. However, the percentage of influenza-positive samples from both sentinel and non-sentinel sources are similar to last week. The number of reported hospitalisations due to severe acute respiratory infection (SARI) remains similar to that seen in the previous several weeks: One influenza detection was reported (influenza B). The number of specimens testing positive for influenza decreased together with the number of samples tested due to the relatively low reporting rate by the countries in the western part of the region caused by holidays this week. Overall, a total of 386 specimens tested positive for influenza in week 51/2012: 275 were type A, and 111 were type B. Of the influenza A viruses, 74 were subtyped: 38 as A(H3N2) and 41 as A(H1N1)pdm09." - Mod.CP
A HealthMap/ProMED-mail map can be accessed at: http://healthmap.org/r/1hiS
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