Flu Scan for Feb 11, 2016

Demographics and flu hospitalization
European flu vaccine protection
Patient-doctor spread of H7N9

High poverty rates associated with higher rates of hospitalization for flu

Influenza-related hospitalization rates and high poverty levels showed a "robust" correlation, according to an analysis of data from 14 states during the 2010-11 to 2011-12 flu seasons published today in Morbidity and Mortality Weekly Report (MMWR).

The age-adjusted incidence of flu-related hospitalization in communities where 20% or more of households were below the federal poverty line (ie, high poverty) was 21.5 per 100,000 person-years (95% confidence interval [CI], 20.7 to 22.4), compared with 10.9 (CI, 10.3 to 11.4) in areas where fewer than 5% of households were below the poverty line (ie, low poverty).

The study found that vaccination rates were lower in areas with a higher poverty level. Unvaccinated persons 65 years of age or older accounted for 94% of hospitalized cases in high-poverty areas, compared with 80% in lower poverty areas.

The authors surmised that lower vaccination rates, greater spread of communicable diseases due to "poverty-related crowding," and a higher frequency of preexisting medical conditions that can increase the severity of influenza were possible explanations for the socioeconomic differences in influenza-related hospitalizations. They recommend that health officials study how to increase vaccination rates and antiviral use outside of hospital settings.
Feb 12 MMWR study


Early European flu vaccine estimate finds lower protection against H1N1

European investigators who track the effectiveness of seasonal flu vaccines released their early findings today, showing a drop in protection against the 2009 H1N1 virus. However, they warned that the late start of Europe's flu season reduced the sample size, which makes their predictions less precise.

Members of the Influenza Monitoring Vaccine Effectiveness in Europe (I-MOVE) network published their findings today on the group's Web site and in a brief report in the latest issue of Eurosurveillance.

Earlier this week European health officials signaled that an influenza B strain mismatch had the potential to hurt the vaccine's effectiveness and they wondered if the emergence of new 2009 H1N1 subgroups would also dampen the impact of this season's vaccine.

The I-MOVE findings are based on case-control studies involving lab-confirmed flu at 10 study sites in Germany, France, Hungary, Ireland, Italy, Poland, Portugal, Spain, Sweden, and the Netherlands. Their early results put overall vaccine effectiveness (VE) for all ages at 46.3% (95% confidence interval [CI], 4.9% to 69.7%). For adults ages 18 to 64 the adjusted VE was slightly lower at 45.2% (95% CI, –12.5% to 73.3%). Assessing overall VE for seniors was hampered by only 14 flu cases in the study.

When the researchers singled out 2009 H1N1 in all ages, overall VE was 44.2% (95% CI, –3.1% to 69.8%), which was lower than in the past four flu seasons, which ranged from 47.5% in 2013-14 to 55% in 2010-11.

Of the 348 lab-confirmed flu cases that turned up in the I-MOVE system during the study period, 246 were 2009 H1N1, 77 were influenza B, 21 were H3N2, and 4 were unsubtyped influenza A. The authors noted that of 37 influenza B strains with known lineage, 36 were Victoria, the type not included in the Northern Hemisphere's trivalent seasonal flu vaccine.
Feb 11 Eurosurveill report
I-MOVE Web site


Chinese H7N9 cluster involves a patient and 2 doctors who cared for him

Two physicians in a Chinese hospital apparently contracted H7N9 avian influenza from a patient last year, according to a letter report in today's New England Journal of Medicine.

The report notes that most human H7N9 cases seem to be acquired from poultry, but a few household clusters involving human-to-human transmission have occurred.

The index patient was a 28-year-old man who had repeated exposures to poultry before he fell ill and was hospitalized in Shantung in January 2015, the report says. He eventually tested positive for H7N9.

A week after the index patient's admission, a 33-year-old doctor who had attended him got sick with a flu-like illness. Four days after that, another attending physician, a 35-year-old man who also had close contact with the first patient, experienced a flu-like illness and bronchial pneumonia.

The virus was confirmed in both of the doctors. All three patients recovered, but the index patient and the first doctor were hospitalized for several weeks. The index patient was still shedding the virus 42 days after he first got sick.

Although the hospital's policy calls for standard infection control practices and the donning of personal protective equipment when caring for H7N9 patients, use of those practices by the two doctors could not be verified, the report states.

A phylogenetic analysis showed that the H7N9 isolates from the three patients and from eight unrelated H7N9 patients hospitalized in 2015 were closely related, but the three viruses from the cluster formed an independent clade. That finding suggests "direct human-to-human transmission; although a common community source cannot be ruled out, no such sources were identified."

The authors conclude that the findings illustrate the importance of using proper infection control practices when caring for H7N9 patients.
Feb 11 N Engl J Med letter

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