Swine Flu Seen as Cresting

NOVEMBER 23, 2009

The current wave of swine flu may have peaked in most of the U.S., but the illness remains widespread and the threat of another wave remains, officials said Friday.

The news came as officials in Norway reported a mutation of the flu virus in two patients who died and one who became severely ill. The mutation, while seen before, appeared to make the H1N1 virus cause infection deeper in the respiratory system than the regular swine-flu virus, a possible explanation for the more-severe cases, Norwegian scientists said.

Swine-flu cases appear to be declining in most of the U.S., the Centers for Disease Control and Prevention said Friday. Flu activity is widespread in 43 states now, down from 46 last week and 48 two weeks ago. Flu cases also appear to have peaked in the U.K. and parts of Western Europe, but are on the rise in Eastern Europe and parts of Asia, the World Health Organization said. But pandemics occur in waves. In the 1957-58 flu pandemic, one wave peaked in the fall and was followed by a second wave in January.

Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases, warned that more flu is circulating now than at the height of many flu seasons, and holiday travel could bring more infections. "It is so early in the year to have this much disease," she said at a news conference. "We don't know if these declines will persist, what the slope will be, whether we'll have a long decline or it will start to go up again."

The CDC estimates at least 22 million Americans have been infected with H1N1 flu, with 3,900 deaths. Dr. Schuchat said 21 U.S. children had died from influenza in the past week, with 15 confirmed to have had H1N1. A total of 171 pediatric deaths have been confirmed since April, although the CDC estimates that more than 500 children have died of the disease.

The Norwegian Institute of Public Health reported on its Web site that it found the change in only three of 70 virus samples from Norwegian cases that they examined, and said it didn't appear to be circulating widely. The mutated virus "might be a result of spontaneous changes which have occurred in these three patients," said Geir Stene-Larsen, the institute's director general.

The WHO and CDC said the mutation has been seen since April in six other countries, doesn't always cause severe disease, isn't widespread, and responds to vaccine and the antiviral medications. "This mutation has been seen sporadically here and around the world," Dr. Schuchat said. Some of the cases were mild, and the H1N1 virus has caused severe lower-respiratory infections without the mutation, she said.

"To date, no links between the small number of patients infected with the mutated virus have been found and the mutation does not appear to spread," the WHO said in a statement. "Although further investigation is under way, no evidence currently suggests that these mutations are leading to an unusual increase in the number of H1N1 infections or a greater number of severe or fatal cases."

U.S. vaccine deliveries picked up after a slowdown last week, with more than 11 million new doses shipped this week to warehouses where they are available for ordering. To date, 54.1 million doses have been shipped to warehouses since early October -- still well behind the government's prediction in August of a delivery of 45 million to 52 million doses by mid-October and 20 million doses weekly for the next several weeks after that.

Health officials are also investigating reports of a growing number of patients with H1N1 viruses that are resistant to oseltamivir, an antiviral drug marketed by Roche AG as Tamiflu. Seasonal H1N1 viruses are widely resistant to the drug, and the WHO has reported 57 cases of oseltamivir resistance in the new H1N1 flu.

The U.K.'s Health Protection Agency said it is investigating likely person-to-person transmission of oseltamivir-resistant swine flu on a hospital ward in Wales. Nine case were reported, and five have been confirmed as resistant to the drug, the agency said in a statement. The cases occurred in people with immunosuppression, which can cause Tamiflu resistance, the agency said. It said the drug-resistant virus wasn't any more virulent than the regular virus. "At present we believe the risk to the general healthy population is low," the agency said.

The CDC and North Carolina officials are investigating four cases of tamiflu-resistant H1N1 flu that occurred over the past six weeks at Duke University Hospital in Durham, N.C. All four patients were in an isolated unit on one floor of the hospital, and were seriously ill with severely compromised immune systems and other medical conditions, officials said.

Write to Betsy McKay at betsy.mckay@wsj.com
Printed in The Wall Street Journal, page A7