US flu activity shifts west as some national markers drop

Jan 11, 2013 (CIDRAP News) – Flu activity indicators showed some wobble last week, which might suggest that activity in the United States is starting to ebb in some locations or could reflect some artifacts of disease reporting that health officials sometimes see over the holiday period.

Officials from the US Centers for Disease Control and Prevention (CDC), however, said at a news conference today that states are reporting a lot of flu, especially with activity starting to rise in some of the far western states.

The California Department of Public Health (CDPH) said today that the state has seen a steady rise in flu activity over the past few weeks. Ron Chapman, MD, MPH, said in a statement that the increase isn't unexpected, and he told the state's residents that it's not too late to get vaccinated.

"Our flu season may not peak for several more weeks, so I encourage everyone to get vaccinated to protect not only themselves, but those with whom they come into contact," he urged.

CDC Director Tom Frieden, MD, MPH, told reporters, "The bottom line is it's flu season, and that may continue for several weeks." He said the season this year is running about a month ahead of schedule and is hard to predict. It may take a few more weeks for health officials to tell if the dip in indicators suggests a flu activity peak or is temporary, he said.

During a typical flu season, health officials usually see elevated levels of influenza-like illness (ILI) for about 12 consecutive weeks, and only time will tell how moderate or severe the current flu season will be, Frieden said.

Joe Breese, MD, chief of the CDC's Influenza Epidemiology and Prevention Branch, said other winter viruses such as norovirus and respiratory syncytial virus (RSV) are circulating alongside flu, which could be fueling some of the news reports about swamped clinics and hospital emergency departments.

Nationally, the percentage of doctors' visits for ILI dropped from 6.0% to 4.3% last week, a level that is still running above baseline for the fifth consecutive week, according to the CDC's latest surveillance report today. Another indictor showing a dip was the percentage of respiratory specimens that tested positive for flu, falling from 35.2% to 32.8% over the past week.

The number of states reporting high ILI activity dropped from 29 to 24 over the past week.

However, the CDC reported rises in other indicators. The percentage of deaths from pneumonia and flu rose slightly above the epidemic threshold for the first time this season, and lab-confirmed flu hospitalizations increased by 1,443 over the past week. The rate is 13.3 per 100,000 population, compared with 8.1 per 100,000 reported the previous week.

The predominant circulating strain in the United States is still H3N2, followed by influenza B.

The CDC received reports of two pediatric flu deaths, one from H3N2 and the other from an unsubtyped influenza A virus, pushing the season's total to 20.

The number of states reporting widespread geographic spread last week rose from 41 to 47, according to the CDC.

The brisk pace of flu cases during the past several weeks have led to fresh reminders about vaccination from state and local health officials, which appears to be one of the factors increasing demand for the vaccine.

Spot vaccine shortages
Frieden said the CDC is hearing reports of spot shortages and is recommending that people seeking the vaccine to call their providers ahead of time to see if they have it. He added that in some instances people may need to call around to locate a vaccine.

Claire Hannan, MPH, from the Association of Immunization Managers, told CIDRAP News yesterday that she hasn't heard of any shortage problems so far except in Massachusetts, which appears to be a local situation in Boston, where city officials declared a public health emergency due to flu earlier this week.

The National Influenza Vaccine Summit is surveying its members to assess the supplies of flu vaccine and hopes to hear back early next week, L.J. Tan, PhD, who cochairs the National Adult Immunization and Influenza Vaccine Summits, told CIDRAP News today.

So far the spot shortages haven't triggered any actions from vaccine makers, but two who responded to queries from CIDRAP News said they are watching the situation. Elizabeth Power, a spokeswoman from Novartis, said the company has shipped 36 million doses of Fluvirin for the US market, which exceeded the 30-million-dose projection it made at the National Influenza Vaccine Summit in 2012.

"We have completed shipments of Fluvirin to the US market for the season. Our distributors may have doses available and we are working with our field based team to address any urgent needs where possible," Power said.

Melissa Garcia, a spokeswoman for MedImmune, the maker of FluMist, said the company has met all of its customer orders for the current season, which amounted to 12 million doses. However, she said that each season the company produces extra doses if more are needed. Of 620,000 additional doses, 250,000 are in reserves for the Vaccine for Children's program and the Department of Defense.

She said the company wouldn't consider making more unless current reserves were used and additional significant demand develops. Garcia added that the company so far isn't seeing additional reorders for this season but is taking orders for next season, when it will be offering the quadrivalent version of FluMist.

Antiviral shortages
Earlier this week a spokeswoman for the US Food and Drug Administration (FDA) confirmed that some areas are experiencing shortages of the oral suspension of the antiviral drug osteltamivir (Tamiflu), typically given to children and others who have difficulty swallowing tablets.

Yesterday the agency posted a notice about the shortage on its Web site, along with resources for pharmacists on how to compound the liquid form of the drug from 75-mg capsules.

Shortages of the Tamiflu oral suspension also occurred during the 2009 H1N1 pandemic and during the 2010-11 flu season. The company has said that it takes significantly more resources to make the liquid suspension compared with the tablets.

Rising levels of flu activity prompted the Canadian government this week to release a supply of oseltamivir from its National Emergency Stockpile, which helps Roche Canada, the drug's maker, to avert any possible shortages.

According to a Jan 4 flu surveillance report from the Public Health Agency of Canada (PHAC), flu activity continues to rise at expected levels for this time of year. Most of the viruses detected so far are influenza A, with H3N2 the predominant strain.

European flu activity
Meanwhile, flu activity in Europe increased substantially over the past week, especially in the northwestern part of the region, according to the latest surveillance report today from the European Centre for Disease Prevention and Control (ECDC).

Norway is the only European country reporting high intensity activity. Seven countries reported medium intensity activity: Belgium, Denmark, Germany, Ireland, Iceland, Slovakia, and Sweden.

The flu virus profile in European countries is still vastly different than patterns seen so far in the United States. The ECDC said testing shows that 44% are influenza A viruses and 56% are influenza B. About half of the influenza A virus are the H1N1 virus, which has so far been detected in very few US samples this season.

See also:

Jan 11 CDC weekly flu surveillance report

Jan 11 CDPH press release

Jan 10 FDA Tamiflu oral suspension shortage notice

Jan 4 PHAC weekly flu surveillance report

Jan 11 ECDC weekly flu surveillance report

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