New data for the 2019-2020 season shows the virus is at a high activity, but disease severity is moderate.
An original version of this article was published on sister publication ContagionLive.
The influenza (flu) virus has reached approximately 13 million people in the US.
According to the newest update to the US Centers for Disease Control and Prevention (CDC) FluView report on data ending January 11, 2020, flu activity is high for the current season, yet disease severity is moderate.
At this point in the season, CDC estimates indicate that there have been 13 million influenza illnesses, 120,000 hospitalizations, and 6600 flu-related deaths.
The CDC notes that the number of respiratory specimens that tested positive for the flu at clinical laboratories decreased over the past week from 23.6% to 22.9%. Visits to clinicians for influenza-like illness also decreased from 5.7% last week to 4.7% this week; however, activity for all US regions remain above baseline. In fact, 34 jurisdictions are experiencing high influenza-like illness activity.
The percentage of deaths attributed to pneumonia and influenza also increased from 6.0% to 6.9%, but remains below the epidemic threshold
According to the report, the overall rate of influenza-associated hospitalization increased to 1.9 per 100,000. The highest rate of hospitalization has been observed among adults aged ≥65 (47.6 per 100,000 population), followed by children aged 0-4 years (34.4 per 100,000 population) and adults aged 50-64 years (23.2 per 100,000 population).
Although influenza B/Victoria viruses have been the national predominant virus this season, new data reveal that during recent weeks equal numbers of B/Victoria and A(H1N1)pdm09 viruses have been reported.
This past week 7 new influenza-associated pediatric deaths were reported, bringing the seasonal total to 39. According to the FluView report, 28 deaths were linked to B viruses—5 of which had their lineage determined and were B/Victoria viruses—and the other 11 deaths were associated with A viruses, 6 of which were A(H1N1)pdm09 virus-associated.
“Unfortunately, [B viruses] seems to be taking a higher toll on very young children, more so than in previous years,” Aaron E. Glatt, MD, a spokesperson for the Infectious Diseases Society of America told Contagion®. “It doesn't necessarily mean that that's something that will continue or it's something that is intrinsically more dangerous to children. It's possible that they haven't been exposed to as much influenza B in their short lives. Even if they're relatively young, they may have seen some influenza A beforehand, and therefore, it's something that their body has somewhat been prepared for.”
Nationally, influenza B/Victoria viruses are the most commonly reported influenza viruses among children age 0-4 years (47% of reported viruses) and 5-24 years (57% of reported viruses). On the other hand, A(H1N1)pdm09 viruses are the most commonly reported viruses among the 25-64 years age group (46% of reported viruses) and 65 years and older (53% of reported viruses).
“From a clinician point of view, stress vaccination, even now,” Glatt, chairman of the Department of Medicine at Mount Sinai South Nassau in Oceanside, New York, and professor of medicine at Icahn School of Medicine at Mount Sinai, told Contagion®. “It’s obviously better to be vaccinated and have whatever benefit the vaccine gives you...and the vaccine will definitely have some benefits.”
The CDC notes that flu vaccine effectiveness estimates are not available yet this season, but vaccination is always the best way to reduce the risk of influenza and any associated complications.
“I personally would add that there is data to support the quadrivalent vaccine,” Glatt noted. “It has 2 strains of B, whereas the trivalent vaccine only has 1 strain. The official position says it doesn’t make a difference, but I would probably recommend the quadrivalent vaccine if they’re both available.”