The current wave of pandemic H1N1 influenza infections is trailing off a little, the Centers for Disease Control and Prevention said this morning, and other indicators seem to confirm that diagnosis. In particular, the numbers of prescriptions written for antiviral agents are declining, and so are diagnostic tests for the virus.
According to the CDC, swine flu activity is widespread in 43 states now, down from 46 last week, but health officials fear a resurgence as people travel around the country for the holidays, carrying their germs with them.
During the week ending Nov. 6, prescriptions for the four antiviral drugs used in combating swine flu fell by nearly 15% to 472,415, the lowest number in several weeks, according to Wolters Kluwer Pharma Solutions of Bridgewater, N.J. The company provides data about prescriptions for the drug to the Food and Drug Administration and independently prepared an analysis for The Times, using a tool called Pharmaceutical Audit Suite.
During the same week in California, however, prescriptions for the four drugs -- more than 90% of them for Tamiflu -- climbed 17.4% to 17,672. The California Department of Public Health reported Thursday that hospitalizations and deaths in the state were declining, but that information is from a week later than the drug data.
During the first week of November, prescriptions for the antiviral drugs rose nearly 26% to 7,394 in the Los Angeles/Long Beach/Santa Ana area; rose 26.5% to 1,436 in the Riverside/San Bernardino/Ontario area; and rose 33.5% to 2,635 in the San Diego/Carlsbad/San Marcos area. Most other areas of the state showed similar increases.
Quest Diagnostics of Madison, N.J., which manufactures a genetic test for swine flu and also uses the test in its commercial testing laboratories, said demand for the test has fallen since Oct. 27 after several weeks of strong demand. In specimens it tested in its own facilities up to Nov. 10, the number that tested positive for swine flu virus has been dropping in all age groups except for people over 65. The decline suggests that many of the patients seeking tests had other respiratory infections. In the over-65 group, the percentage of positive tests has tripled since late August and is now at 14%, the company said. The proportion of positive tests for swine flu has dropped across the country except for the Northeast, where it has doubled in the two weeks ending Nov. 10.
In other swine flu news:
-- Health authorities around the world have been on the lookout for cases of Tamiflu-resistant swine flu virus, fearing that a wide spread of resistant strains would make treating infections much more difficult. So far, about 50 cases have been identified, including two clusters observed this week -- a group of four cases in North Carolina and a group of five in Wales. All four of the North Carolina patients were hospitalized and were very ill with underlying severely compromised immune systems and multiple other complex medical conditions, according to researchers from the Duke University Medical Center. Three of the four died. No details have been released about how the patients caught the resistant virus or whether there was any contact among them.
Five patients at University Hospital of Wales in Cardiff were identified with Tamiflu-resistant swine flu infections, and three of them appear to have caught it in the hospital. The only previous case in which transmission of a resistant virus is thought to have occurred involved two youths at a North Carolina camp this summer. In other patients, the virus developed resistance while they were being treated and they did not pass it on to anyone. Two of the five patients have recovered, one is in critical care, and two are receiving normal care.
-- A batch of about 170,000 doses of swine flu vaccine manufactured by GlaxoSmithKline has been recalled in Canada after health officials noticed an unusually high number of allergic reactions to the vaccine. Most of the cases involved immediate anaphylactic reactions to the vaccine, and recipients were treated on site by medical personnel at the immunization clinics. No lasting effects of the allergic reaction have been observed. Glaxo said it is investigating the batch to see if there is anything unusual about it.
-- Thomas H. Maugh II