Influenza activity in Texas during the 2017-2018 season

The Texas Influenza Surveillance report produced on March 16, 2018 includes information on laboratory results, the total number of patients with an influenza-like illness (ILI) reported by providers in the Texas ILINET, and the number of pneumonia and influenza deaths occurring in Texas. There was a definite increase in the number of positive influenza tests (antigen, culture, PCR) reported by Texas Hospital laboratories starting in November 2017. This number peaked during the first two weeks of February and then dropped off significantly in the last week of February and first two weeks of March. These results included 131,108 specimens tested during this season through the week ending March 10, 2018, with 33,439 positive results. Tests were positive for both influenza A (67.01% of the tests) and influenza B (32.99%). Most of the positive influenza A tests were for H3N2 virus. Other viruses identified included adenovirus, human metapneumovirus, parainfluenza virus, rhinovirus, respiratory syncytial virus, and seasonal coronavirus. The most frequent positive tests were to rhinovirus (25.1% of the tests performed) and human metapneumovirus (8.02% of the tests performed).

The Texas Influenza-Like Infection Network (ILINET) includes approximately 100 providers who reported ILI cases from the 40th week of 2017 through the tenth week of 2018. More than 10% of the patients seen by these providers had an influenza-like illness during the week starting in the 51st week of 2017 through the seventh week of 2018. The number of deaths secondary to pneumonia and/or influenza between October 1, 2017 and March 10, 2018 was 6006. The most frequent mortality (4694 deaths) occurred in individual 65 + years who had a mortality rate of 128 per 100,000.

The CDC reported that the overall effectiveness in the vaccine used in this 2017-2018 season was 36% (95% confidence interval 27-44%). The effectiveness was 25% against influenza A (H3N2) virus infection, 67% against influenza A (H1N1) virus infection, and 42% against influenza B virus infection. There was statistically significant protection for children aged 6 months through 8 years and adults aged 18 through 49 years. There was no protection observed in children 9 through 17 years of age and in adults older than 50 years of age. The CDC recommends influenza “antiviral treatment for any patient with suspected or confirmed influenza who is hospitalized, has severe or progressive illness, or is at high risk for complications from influenza, regardless of vaccination status or results of rapid, point-of-care influenza diagnostic tests.” K Nugent-3-30-2018.

1. Texas influenza surveillance report 2017-2018 Season/MMWR Week 10. at Current extended flu activity report (pdf).—2018-Texas-Influenza-Surveillance-Activity-Report.aspx.

2. Flannery, Chung JR, Belongia EA, et al. Interim estimates of 2017–18 seasonal influenza vaccine effectiveness—United States, February 2018. MMWR Morb Mortal Wkly Rep 2018 Feb 16; 67(6): 180–185.

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