June 2010.  Flu activity has all but disappeared in the United States after a slight resurgence from February to April in the US Southeast. Only one state (Hawaii) was reporting local activity as of the final CDC report for the 2009-2010 season (May 30), while the rest of the states reported sporadic acitivity or no activity at all. The percentage of visits to clinics and emergency departments for influenza like illness has declined to the summer baseline. The second wave of the 2009 H1N1 pandemic is over.

The last Pediatric death due to 2009 H1N1 occurred in March 2009. From April 2009 to May 2010 there were a total of 285 deaths in children due to the Swine Flu and another 53 deaths from influenza isolates that were not further characterized.  The overall mid-point estimate of deaths in all age groups due to pandemic 2009 H1N1 is approximately 12,000.

Some perspective on the pediatric deaths    Each year since 2004, CDC has tracked the number of pediatric deaths due to seasonal flu (winter season flu). In the 2003-2004 flu season, 154 children died throughout the nation from “Fujian flu”, a particularly severe strain. Since then, the number of deaths nationally has ranged from 78 to 117 per flu season. There are approximately 75 million children under age 18 living in the United States. Approximately 2,000 children die each year in auto accidents.

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April 30, 2010. Week 16. Flu activity has declined significantly nationwide. Only two states (Alabama and South Carolina) are reprting local activity of influenza, while the rest of the country is reportitng either sporadic activity or none at all. The percentage of visits to clinics and emergency departments for influenza like illness has declined almost to the summer baseline . There have been no pediatric deaths due to influenza anywhere in the US  in the past two weeks. The total number of children known to have died from influenza in the past year include 272 since the “second wave” of 2009 H1N1 appeared in late August 2009, and an additional 65 who succumbed during the “first wave” of Swine Flu from April to August 2009.

Impact in All Age Groups Deaths and hospitalizations due to flu remain very low although flu activity has not disappeared. CDC reports 2,125 laboratory confirmed deaths due to flu in the United States since August 2009. However, this is likely an undercount, since many cases are not reported or are undetected. The CDC estimates that as of February 2010, approximately 59 million people nationwide have been infected by 2009 H1N1, and 12,000 have died. Click here for more information from CDC.

World Wide Impact Flu  activity is down throughout the world. The primary focus for continued 2009 H1N1 appears to be West Central Africa and South East Asia. There is little flu activity in the temperate regions of the Norther Hemispere (North America, Europe). As of April 30, there was only sporadic activity of flu in the Southern hemisphere. The winter flu season in the Southern hemisphere generally begins in May or June. The WHO reports “at least” 17,919 confirmed deaths due to 2009 H1N1 throughout the world, although this is likely only a small proportion of the actual number of deaths.

Click here to read more from the World Health Organization.

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March 22, 2010. Week 10.  Most states in the US are reporting either sporadic influenza activity or none at all. A notable exception is a collection of 10 contiguous states in the South that are reporting regional (3) or local (7) activity. There were two deaths due to flu reported  in US children last week, for a total of 331 pediatric deaths since the pandemic began in April 2009. H1N1 caused all but three of the deaths among cases where isolates were fully subtyped.

Impact in All Age Groups    Deaths and hospitalizations overall are at their lowest levels since the “second wave” of H1N1 began in August 2009. The latest CDC estimates as of Jan 16 2010:

57 million people in the US have been infected by H1N1 since April 2009

257,000 hospitalized for H1N1

11,690 deaths due to H1N1

The CDC reports that 5.9% of  influenza tests submitted nationally last week were positive, a slight increase over the prior week. 98% of the flu A isolates further characterized were 2009 H1N1, and 2% of the isolates were influenza B. Isolation of isolates other than novel H1N1 “Swine Flu” has been rare throughout the 2010 winter season.

For the latest CDC 2009 H1N1 update (March 19) please click here.

For an update on the situation internationally please click here.

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Feb 19, 2010. Week 6.  There are now three states reporting Regional flu activity, all in the Southeast, the only region of the country with substantial flu still being reported. Less than 5% of specimes submitted for influenza culture in the past week have been positive for flu, down from a high of over 50% in the fall. While hosptilizations and deaths nationally have decreased markedly since their October highs, there does appear to be a slight increase in deaths over the past 3-4 weeks. There were two additional deaths in pediatric patients reported last week, for a total of 326 since April 2009.

Impact in all age groups  Hospitalizations and deaths are far below their October highs. Flu activity is markedly down but not completely gone. There have been only scattered reports of seasonal flu; virtually all of the influenza currently in circulation is still H1N1.

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Jan 2, 2010. Week 52. Only one state in the US (Alabama) is now reporting widespread H1N1 activity.  Four of 10 national regions now report mildly elevated levels of influenza-like illness (ILI), and 6 report normal levels. Four deaths in children due to H1N1 were confirmed nationally this week. The total number of pediatric deaths proven or likely due to H1N1 since the second wave began in August is now 228, compared with 63 deaths from April to August 30.

Impact in all age groups   The total number of hospitalizations and deaths due to H1N1 have been trending down for 9 consecutive weeks

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Dec 24, 2009  Week 50. The number of flu-related hospitalizations and deaths nationwide has been declining steadily for the past 6-8 weeks after peaking in week 43. Seven of ten US regions now report visits for ILI below region specific levels. Nine influenza related pediatric deaths were reported this week. The number of pediatric deaths due to flu has been on a sharp downward trajectory nationally for at least four weeks. The number of laboratory confirmed pediatric deaths due to influenza since August 30 is 221, and the total since the pandemic began in April is 285.

Impact in all age groups  Pneumonia and influenza mortality as a percentage of all US deaths was at 7.2% this week, which puts it below the empidemic threshold for the first time in 11 weeks. The CDC monitors P & I mortality in 122 cities around the coutry throughout the year as a way to assess the severity of an influenza outbreak. P & I mortality was above the epidemic threshold from week 40 (Oct 10) until this week. This indicates that the worst of the second wave of H1N1 is now behind us.

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Dec 11, 2009    There were 16 flu-related pediatric deaths reported nationally  this week, 13 of which were confirmed to be due to H1N1. The total number of confirmed deaths in children due to H1N1 is 165 since Aug 30 and 224 since the virus first appeared in late April.

Impact in all age groups  The CDC stopped counting the total number of individual cases of H1N1 in mid-summer. At that time, it became clear that it was impractical to keep up with every case of H1N1 “Swine Flu”, since both diagnosis and treatment from that point in the pandemic onward have been based on symptoms, not on the results of laboratory tests for H1N1.

In mid-November, the CDC began to post estimates for the total number of people infected, total hospitalized, and the total number of deaths. These numbers are no longer based on reporting alone, since it became clear that there was substantial underreporting in all of these categories.

The latest update from the CDC, which was posted on Dec 10, incorporated data received up to Nov 14. Based on these data, the CDC estimates that since April 2009 about 50 million people have been infected by H1N1, 213,000 have been hospitalized, and 9,820 have died, including 1,090 children from 0 to 17 years of age. Click here to see the CDC webpage that explains these numbers.

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Nov 20, 2009    There were 21 flu related pediatric deaths from around the United States this week. There have been a total of 171 deaths in children confirmed to be due to H1N1 since April of this year and another 28 deaths due to flu that were not further identified.

Impact in all age groups   Since the H1N1 pandemic began in April the CDC has received reports of about 1,200 deaths confirmed to be due to H1N1 influenza. However, this is probably an undercount, since many patients have died without any tests or too late in the illness to detect the virus. CDC has developed methodology to estimate the number of people infected, the number hospitalized, and the number of deaths. This is done to provide a more accurate description of the impact of this pandemic. The first such estimate was posted in Novermber, and included the total from April to October 17. The CDC estimates that approximately 22 million people have been infected by H1N1, 98,000 have been hospitalized, and 3,900 have died.

Click here for the full CDC report.

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Oct 31, 2009    There were 18 deaths due to influenza in children reported to CDC this week, including 15 with proven H1N1. Since Aug 30, when the “second wave” of H1N1 was becoming evident nationwide,  there have been 85 pediatric deaths due to flu including 73 with proven H1N1. In the 6 months since H1N1 appeared on April 28, 145 US children have died from flu including 129 with proven H1N1.

Impact in all age groups    Nationally, 17,838 people of all ages have been hospitalized with laboratory confirmed H1N1 influenza since Aug 30, and 672 of those patients died (3.8%). However, this probably underestimates the number of deaths due to H1N1 since many people who are late in the course of the complications from flu may not have a positive RT-PCR confirmatory test. The CDC also tracks deaths due to pneumonia and influenza in 122 cities nationwide. The proportion of deaths due to pneumonia and influenza expected for this week in a “normal” year is 6.7%. Currently the 122 cities are reporting pneumonia and influenza to be the cause of death in 7.4% .

Nationally the proportion of visits to clinics and emergency departments for influenza like illness is down slightly after 4 weeks of increase.

Click here to see the data from CDC on deaths due to H1N1.

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Oct 24, 2009      There were 22 flu-related pediatric deaths reported this week; 19 of these deaths were confirmed 2009 H1N1, and three were influenza A viruses, but were not subtyped. Since April 2009, CDC has received reports of 114 laboratory-confirmed pediatric 2009 H1N1 deaths and another 12 pediatric deaths that were laboratory confirmed as influenza, but where the flu virus subtype was not determined. 65 of the laboratory confirmed deaths due to H1N1 in children occurred after Aug 30, when H1N1 began its “second wave” nationally.

Impact in all age groups    Nationally, 12,466 people of all ages have been hospitalized with laboratory confirmed H1N1 influenza since Aug 30, and 530 of those patients died (4.25%). However, this probably underestimates the number of deaths due to H1N1 since many people who are late in the course of the complications from flu may not have a positive RT-PCR confirmatory test. To get a better estimate of deaths due to flu, CDC also tracks deaths due to pneumonia and influenza nationwide. Since Aug 30, there have been 25,985  hospitalizations for pneumonia and influenza, and 2,916 deaths.

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Oct 1, 2009      Nineteen influenza-associated pediatric deaths were reported to CDC during week 39 (Alaska, Arizona, Colorado, Florida, Maryland [2], North Carolina, Oklahoma, Tennessee [3], Texas [7], and Wisconsin). Sixteen of these deaths were associated with 2009 influenza A (H1N1) virus infection and three were associated with influenza A virus, for which subtype is undetermined. These deaths occurred between July 19 and October 3, 2009. Since September 28, 2008, CDC has received 147 reports of influenza-associated pediatric deaths that occurred during the current influenza season (28 deaths in children less than 2 years, 15 deaths in children 2-4 years, 45 deaths in children 5-11 years, and 59 deaths in individuals 12-17 years). Seventy-six of the 147 deaths were due to 2009 influenza A (H1N1) virus infections, and 29 of these have occurred since August 30, 2009.