Flu Scan for Jun 03, 2016

Flu immunity from previous infection
Low US flu levels
Avian flu in Mexico, Niger

Flu episode may yield years of future protection against same virus subtype

A study from Spain suggests that people who are infected by the influenza A viruses H3N2 or H1N1 may have better than 60% protection against new infections by the same subtype for several years afterward, according to a report in yesterday's issue of Eurosurveillance.

The researchers aimed to learn the extent to which (1) flu episodes within the past 5 years and (2) current trivalent influenza vaccine (TIV) prevented lab-confirmed flu cases in Navarre, Spain, in the 2013-14 flu season.

They enrolled 1,170 patients with medically attended flu-like illness (MA-ILI), including 645 in hospitals and 525 in primary care clinics. Of those, 589 tested positive for flu, all of them for type A viruses, and 581 served as negative controls.

The team defined MA-ILI due to a specific virus subtype in the previous five seasons as a laboratory-confirmed flu infection with the same subtype or MA-ILI during weeks when more than 25% of samples were positive for this subtype. It was possible to use the second criterion, they said, because one subtype was clearly dominant in Navarre in each of the five preceding seasons.

The researchers found that patients previously infected with the 2009 H1N1 virus had 63% protection (95% confidence interval [CI], 16%-84%) against infection with H1N1 in the 2013-14 season, and those who had a previous H3N2 infection had 65% protection (95% CI, 13%-86%) against another H3N2 illness.

Protection provided by the vaccine was considerably lower, the analysis showed. Overall adjusted vaccine effectiveness (VE) was 31% (95% CI, 5%-50%). By subtype, VE was 45% (95% CI, 12%-65%) for H1N1 and 20% (95% CI, −16%-44%) for H3N2.

"Our results suggest low to moderate influenza VE in the 2013/14 season," the authors wrote. "While not entirely satisfactory, this result is important in terms of individual and public health.

"Previous influenza episodes were highly effective against new influenza illness by the same virus subtype, and this effect seemed to persist over various seasons, which may point to possible avenues of obtaining better vaccines against influenza," they added. "In any case, annual influenza vaccination remains the principal preventive option in persons at high risk of developing complications if they contract influenza."
Jun 2 Eurosurveill report


US flu activity stays low, but 4 deaths in kids reported

US influenza activity stayed at low levels typical for this time of year, the Centers for Disease Control and Prevention (CDC) said today in its weekly update, though four new flu-related deaths in children were reported.

Just 1.5% of visits to sentinel clinics were prompted by influenza-like illnesses last week, up a bit from 1.3% a week earlier and well below the national baseline of 2.1%, the CDC said. Deaths attributed to pneumonia and flu, as reported by the 122 Cities Mortality Reporting system, also inched up a bit to 6.3% last week from 6.0% the previous week. The epidemic threshold for the week is 6.5%.

The 4 flu-related deaths in children compared with 2 the previous week and raised the season total to 74. Two deaths were tied to the 2009 H1N1 virus and occurred in late April and early May. Another one, from March, was attributed to an influenza A virus that was not subtyped. The fourth was caused by type B in late March or early April.

The 74 pediatric deaths compare with 171, 111, and 148 in the previous flu seasons.

The CDC has switched to an abbreviated version of FluView for its weekly report, an indication that the country is between flu seasons.
Jun 3 CDC FluView update


Avian flu outbreaks reported in Mexico, Niger

In separate reports to the World Organization for Animal Health (OIE) on Jun 1 and 2, government officials confirmed an outbreak of highly pathogenic avian influenza (HPAI) H7N3 in Mexico and an outbreak of HPAI H5N1 in Niger.

In Mexico, H7N3 was detected on May 11 on a farm containing 151,000 commercial layers in the town of Sayula, Jalisco. Cases were identified in 15 birds as a result of active surveillance, agriculture officials said, noting that the birds showed no clinical signs of illness. Depopulation of the affected farm is currently under way.

In Niger, an outbreak of H5N1 began Feb 21 on a farm of layers in the country's capital city of Niamey, located in the southwestern Tillaberi region. All 86,000 chickens on the farm were sickened and died, officials said. Potential sources of infection reported to the OIE include "introduction of new live animals" and "fomites (humans, vehicles, feed, etc.)."
Jun 1 OIE report on H7N3 outbreak
Jun 2 OIE
report on H5N1 outbreak

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