CDC sees some signs of an early flu season

Flu activity in the United States continues to rise, and several markers are higher than normally seen this early in the flu season, the US Centers for Disease Control and Prevention (CDC) said yesterday in its weekly update.

Three southeastern states are reporting high or widespread flu activity, and the CDC said it received reports of five more pediatric flu deaths. In its report, which covers the week ending Nov 18, the CDC also reported one more novel flu infection, an H1N1 variant (H1N1v).

Globallly, flu activity in the Northern Hemisphere is rising, with H3N2 and influenza B the most frequently detected strains, the World Health Organization (WHO) said yesterday in an update.

Flu builds steam in South, Northeast

Nationally, the percentage of clinic visits for flulike illness is still below the national baseline of 2.2%, but 4 of the CDC's 10 regions are already at or above their regional baselines—an area that includes most of the South as well as several Northeastern states.

At clinical labs, influenza A accounted for 83.4% of positive flu specimens, and, of subtyped influenza A samples, 78.1% were H3N2. Most viruses collected since May 21 are antigenically and genetically similar to cell-grown strains in the current flu vaccine.

Surveillance on flu hospitalizations shows a cumulative overall rate of 1.4 per 100,000 people, with the highest rates in people 65 and older, followed by adults ages 50 to 64 and children younger than 5.

Of the five pediatric flu deaths reported to the CDC, one was from the previous season. The others occurred in late October or November, two attributed to H3N2, one to 2009 H1N1, and one to an unsubtyped influenza A virus. So far five pediatric flu deaths have been reported for the current season.

Two states—Louisiana and Mississippi—reported high flulike illness activity, a marker based on clinic visits. Geographic activity for flu was reported as widespread in two states: Louisiana and Oklahoma. Guam and six states (Arkansas, Georgia, Kentucky, Massachusetts, Mississippi, and South Carolina) reported regional spread.

H1N1v infects Iowan

In other US flu developments, the CDC said Iowa reported an H1N1v infection in an adult who had direct contact with pigs before symptoms began. The patient, who is younger than age 50, wasn't hospitalized and has fully recovered.

No human-to-human transmission was detected. The CDC said the illness marks the first H1N1v case in the United States for 2017 and brings the total number since 2005 to 21.

So far this year, the CDC has received reports of 66 variant flu cases. Most involved H3N2v, though four were H1N2v. Among the patients infected with variant strains, 6 were hospitalized, and all have recovered.

Northern Hemisphere flu rise

In its update yesterday, the WHO said that, as of Nov 12, flu activity rose slightly in temperate Northern Hemisphere zones, while temperate Southern Hemisphere areas have generally seen flu decline to interseasonal levels.

In North America, a continuing increase in flu has been led by H3N2, while flu in Europe is still low, with H3N2 and influenza B as the dominant strains.

Respiratory illness indicators are on the rise in some Central Asia countries, including Kazakhstan, Tajikistan, and Uzbekistan. In northern China, H3N2 activity has increased slightly in recent weeks, the WHO said.

Globally, 67% of flu specimens tested were influenza A, and of subtyped influena A viruses, 79% were H3N2. Of influenza B viruses, 78% belonged the Yamagata lineage.

See also:

Nov 27 CDC weekly FluView report

Nov 27 CDC flu situation update

Nov 27 WHO global flu update

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