According to reports from the Centers for Disease Control and Prevention (CDC), influenza is still strengthening in the United States and is not expected to decrease for at least several more weeks.
In addition, this season’s vaccine is only 58% compatible with B / Victoria, the strain that is especially affecting children.
“It’s not a very good combination for B / Victoria,” Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, told CNN. “It’s not a horrible game, but it’s not a very good game.”
Nationally, the predominant virus is B / Victoria, followed by the A (H1N1) pdm09 viruses, and the predominant virus varies by region and age group. The A (H3N2) and B / Yamagata viruses are circulating in low numbers.
“The key indicators that track flu activity remain high, but the indicators that track severity are not high at this time of the season,” the CDC explains in the report.
Although levels of outpatient visits for influenza-like illness (ILI) remain high, hospitalization rates and the percentage of deaths resulting from pneumonia and influenza remain low.
“This is probably due to the prevalence of pdm09 influenza B / Victoria and influenza A (H1N1) viruses that are more likely to affect children and adults younger than the elderly. Because most hospitalizations and deaths occur between people 65 years of age or older, with fewer illnesses among that group, we expect, at the population level, to see less impact on hospitalizations and deaths related to the flu, “explains the CDC.
Outpatient visits by ILI activity fell from 7% the week before to 5.8%. “The decrease in the percentage of visits of patients with ILI may be influenced in part by changes in the behavior of seeking medical attention and the transmission of influenza virus that may occur during the holidays,” the CDC said in its report .
At the regional level, the percentage of outpatient influenza visits ranged from 3.6% to 8.6%, and all regions reported a percentage of outpatient influenza visits that were equal to or greater than the baselines specific to their region.
The percentage of respiratory samples that tested positive for influenza in clinical laboratories fell to 23.6% from 26.4% during the last week of 2019.
ILI activity was high in the District of Columbia, New York City, Puerto Rico and 33 states; moderated in six states (Alaska, Indiana, Michigan, Minnesota, Rhode Island and South Dakota); and low in eight states (Florida, Hawaii, Missouri, Montana, Nevada, Ohio, Vermont and Wyoming).
The activity was minimal in New Hampshire and there was insufficient data to calculate ILI activity for Delaware, Idaho and the US Virgin Islands. UU.
Geographically, influenza activity was widespread in Puerto Rico and 46 states, regional in three states (Mississippi, North Dakota and Vermont), local in the District of Columbia and Hawaii, and sporadic in the U.S. Virgin Islands. Guam did not report.
Hospitalizations and deaths
According to CDC estimates, there have been at least 9.7 million illnesses, 87,000 hospitalizations and 4800 influenza deaths this season.
Between October 1, 2019 and January 4, 2020, 4228 laboratory-confirmed hospitalizations were reported. Of these, 2299 (54.4%) were related to influenza A virus, 1906 (45.1%) to influenza B virus, 13 (0.3%) to influenza A virus and coinfection of the influenza virus. influenza B, and 10 (0.2%) with the influenza virus, which had not been typed.
Among the patients for whom information on the influenza A subtype was available, 461 (86.0%) were virus A (H1N1) pdm09 and 75 (14.0%) were virus A (H3N2).
The cumulative overall hospitalization rate was 14.6 per 100,000 inhabitants. The rate was higher for those over 65 (33.3%), followed by children under 5 (26.8) and those aged 50 to 64 (17.0).
The percentage of deaths from pneumonia and influenza increased to 5.8% (epidemic threshold 6.9%), from 5.5% during week 52 of 2019.
During week 1 of this year, the CDC received reports of five pediatric influenza-associated deaths that occurred during the weeks ending December 28, 2019 and January 4, 2020. Three of them were related to influenza B for which the lineage was not determined, and two were related to influenza A (H1N1) pdm09 viruses.
So far, the CDC has received reports of 32 pediatric deaths associated with influenza that occurred this season, compared with 16 at this time last season. Of these, 21 deaths were related to influenza B viruses, five of which had a certain lineage and all were B / Victoria virus. Eleven deaths were related to influenza A viruses, six of which underwent subtyping and were all A (H1N1) pdm09 viruses.
Influenza B viruses can cause serious diseases in adults and children; however, adults often have accumulated immunity from previous infections, while children may not have it.
Both influenza A viruses and influenza B viruses can cause serious illness in adults and children; Therefore, the CDC recommends vaccination for all persons over 6 years of age and antiviral medications as soon as possible after the onset of the disease.
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