The number of US states reporting high influenzalike illness activity doubled during the week ending December 29, and a spot-check of major drug chains revealed that only one had a recently approved antiviral medication in stock.
The US Food and Drug Administration recently approved baloxavir marboxil (Xofluza, Genentech) for those aged 12 years or older with flu symptoms for no more than 48 hours. Baloxavir is a single-dose, oral medication that should be taken within 48 hours of symptom onset to be most effective. It may be more appealing to patients than other antiviral medications that must be taken for several days, such as oseltamivir (Tamiflu, Genentech), zanamivir (Relenza, GlaxoSmithKline), and peramivir (Rapivab, Seqirus).
Baloxavir may be difficult to obtain, based on telephone calls to major drug chains in six locations last week, according to a report by WebMD. Of stores in Los Angeles, Chicago, New York City, Minneapolis, Atlanta, and Kankakee, Illinois, the store in Minneapolis was the only one that had baloxavir in stock. All of the pharmacies offered to order it, but they gave various answers about how long it would take to get the drug.
Influenza Activity Intensifies but Remains Below Last Flu Season
During week 52, the proportion of outpatient medical visits for influenzalike illness was 4.1%, up from 3.3% last week and lower than last season at this time, when the proportion was 5.8%. The national baseline was 2.2% for both seasons.
Since October 1, 2018, the Influenza Hospitalization Surveillance Network (FluSurv-NET) has received reports of 1562 laboratory-confirmed influenza-associated hospitalizations, much lower than the 3927 reported during the same period last year.
All 10 regions had influenzalike illness at region-specific baseline levels or above, as they had at this time last season.
Although the number of states reporting high influenzalike illness activity doubled during week 52, it still remained below this week last year, when high activity was reported in New York City and 26 states.
The levels of moderate influenzalike activity were similar during week 52 of this season and last season: This season, nine states reported moderate activity, up slightly from Puerto Rico and seven states the week before. During week 52 of last season, Puerto Rico and nine states reported moderate activity.
Influenzalike illness activity was low in the District of Columbia and 10 states compared with the District of Columbia and six states at this time during the 2017-2018 influenza season. Activity was minimal in Puerto Rico and 12 states this season and minimal in nine states at this time last year.
The geographic spread of influenza was widespread, in 24 states during week 52, more than twice as high as the previous week, when it was widespread in Guam and 11 states. By week 52 of the 2017-2018 season, influenza was widespread in 46 states — everywhere except Hawaii, Maine, New Hampshire, New Jersey, and the District of Columbia.
Puerto Rico and 18 states experienced regional activity during week 52.
Hospitalizations Edging Up but Still Lower Than Last Season
The cumulative rate of laboratory-confirmed influenza-associated hospitalizations was 5.4 per 100,000 population, up from 3.6 during week 51. The rate was much higher during week 52 of the 2017-2018 season, when it was 13.7 per 100,000 population.
The highest hospitalization rate was among children younger than 5 years, at 14.5 hospitalizations per 100,000 population, compared with 9.9 during week 52 of last year.
The proportion of deaths caused by pneumonia and influenza was below the National Center for Health Statistics Mortality Surveillance System’s epidemic threshold.
The CDC received reports of two influenza-associated pediatric deaths during week 52, both associated with influenza A(H1N1)pdm09 viruses. One child died during the week ending December 22 and the other during the week ending December 29. The total number of pediatric deaths from influenza this season is now 13.