Jan 18, 2013 (CIDRAP News) – This year's edition of influenza is hitting the elderly hard, putting many in hospitals, even as overall flu activity is showing signs of slowing down, the Centers for Disease Control and Prevention (CDC) said today.
"We're in the middle of flu season, about halfway through, and it's shaping up to be worse than average and a bad season particularly for the elderly," CDC Director Thomas Frieden, MD, MPH, said at a noontime media briefing.
"Last week hospitalization rates increased sharply in people 65 and over, and this week they increased sharply again, going up to 82 per 100,000, which is quite a high rate," he said, referring to numbers in the CDC's weekly flu activity update. The cumulative all-ages hospitalization rate is 18.8 per 100,000.
Frieden said those numbers are comparable with other recent tough flu seasons when influenza A/H3N2 was the dominant strain, including 2007-08 and 2003-04. The figures represent cumulative, lab-confirmed flu cases involving hospitalization in the elderly population this season.
Concerning the general flu picture, he said, "Many parts of the country are still seeing high and in some parts of the country increasing activity, while overall activity is starting to go down."
One flu marker that dropped last week was the share of medical outpatient visits caused by influenza-like illness (ILI), which was 4.6%, according to the CDC's update. The previous week, ILI visits were at 4.8%. The national baseline is 2.2%.
Joe Bresee, MD, head of the CDC's Influenza Epidemiology and Prevention Branch, explained that ILI visits for the previous week (the first week of January) were originally pegged at 4.3%, but the number was revised to 4.8% as a result of reports that came in after the CDC first published the update for that week (on Jan 11).
The proportion of respiratory samples that tested positive for flu last week was 29.4%, down a bit from the 32.8% reported a week earlier. But several other flu markers were higher.
High activity in 30 states
Thirty states reported high flu activity, up from 24 states the previous week. Another 10 states cited moderate activity, with the rest reporting minimal or low numbers. Cases were geographically widespread in 48 states.
Deaths attributed to pneumonia and flu were at 8.3% last week, exceeding last week's 7.3% and the epidemic threshold for this time of year, also 7.3%, the CDC said.
Nine pediatric deaths reported last week were attributed to flu, raising this season's total to 29. Frieden said that figure is well below the 153 children who died of flu in the 2003-04 season, but he added, "We expect the number of hospitalizations and deaths to rise further in the next week or so as the season progresses and people develop complications."
Of the nine deaths noted last week, two involved H3N2 viruses, four involved type A viruses that were not subtyped, and three were related to type B viruses, the CDC said.
Frieden said the CDC is continuing to hear reports of spot shortages of flu vaccine, but he said most people should still be able to get a dose if they look around.
He reiterated what the CDC said in a notice earlier this week: that vaccine manufacturers have increased their estimated production totals for this season. The estimate is now 145 million doses, compared with 135 million doses cited previously.
"As of this week about 129 million doses have been distributed; that means there is more vaccine out there for providers to order," he said. But he added that certain formulations may not be available, particularly those for young children.
In response to questions, Frieden said the higher estimate probably means that earlier estimates were too cautious, not that there was a late surge in production. "Sometimes the initial yield is somewhat unpredictable, so they'd rather underestimate and overdeliver, and that's what we've probably seen this year," he commented.
He noted that providers can use the online Influenza Vaccine Availability Tracking System (IVATS) to locate vaccine. Also, providers and consumers can use the "Flu.gov" web site to find out where vaccine doses are available locally, he said.
Frieden emphasized the need for early antiviral treatment for patients who have an increased risk of flu complications, including the elderly, young children, and those with underlying health conditions. As CDC officials have said before, he noted that the rate of antiviral treatment in flu patients has dropped from what it was in the 2009 pandemic.
"We're still seeing in preliminary analysis of this season that we're not doing as well as we should be doing at getting people treated promptly," he said, adding that as many as a third to half of patients for whom prompt antiviral treatment is appropriate aren't getting it.
Addressing liquid Tamiflu supply
At the briefing, Margaret Hamburg, MD, commissioner of the US Food and Drug Administration (FDA), announced a new step to address spot shortages of the liquid suspension form of oseltamivir (Tamiflu). The liquid form is used in some children and others who have trouble swallowing capsules.
As reported previously, pharmacists can use 75-mg oseltamivir capsules to make the suspension, which Hamburg said is used in children younger than 1 year of age. She said 75-mg capsules are available, but the supply may run low if many pharmacists use them to prepare the liquid formulation.
Consequently, "The FDA is now allowing Genentech [the manufacturer] to distribute 2 million units of 75-mg capsules that have an older version of the package insert," she said. The medicine is approved and up-to-date, but some of the insert information is outdated.
"Repackaging would take many weeks, which we don't have this flu season," Hamburg said in explaining why the FDA authorized Genentech to distribute the medication.
Flu trends in Europe
Flu activity continued to increase in much of Europe last week, the European Centre for Disease Prevention and Control (ECDC) reported today.
Nineteen countries reported increasing transmission, while 14 cited "medium or high intensity" activity, the ECDC said. The harder-hit areas are mostly in northwestern Europe.
The proportion of sentinel respiratory specimens that tested positive for flu remained high at 42%, similar to the previous week's level, the agency said.
For the season so far, 47% of isolates tested were type A and 53% were type B. Of type A viruses, 48% were H3N2 and 52% were 2009 H1N1. That contrasts sharply with the United States, where H3N2 is overwhelmingly dominant and H1N1 isolates have been rare.
The ECDC said 383 lab-confirmed flu cases requiring hospitalization have been reported this season.
Elsewhere, many countries in temperate parts of Asia have been seeing expanded flu activity, the World Health Organization (WHO) said in its biweekly update today.
The WHO also noted that:
- Some countries in the eastern Mediterranean and North Africa have reported declining flu detections.
- Persistent low-level flu circulation has continued in tropical Asia.
- Flu activity has decreased in most countries in sub-Saharan Africa.
- In the Caribbean, Central America, and tropical South America, flu dropped to low levels, except in Bolivia, where H3N2 cases are growing in number.
Concerning the virologic picture, the WHO said that among close to 46,000 flu isolates tested in its affiliated labs so far this season, 78.7% were type A and 21.3% were type B. Of the A viruses, 87.6% were H3N2 and 12.4% were 2009 H1N1.
CDC Fluview update
Jan 18 ECDC flu update
Jan 18 WHO flu activity update
Jan 18 WHO flu virology update
Jan 17 Pan American Health Organization flu update
IVATS flu vaccine tracking site