The annual flu has arrived in the United States and has killed at least one child, the Centers for Disease Control and Prevention reported on Thursday.
The influenza season is off to a slow start, the CDC said in its weekly report on death and disease. "Twenty states and the District of Columbia reported no influenza activity," the CDC said.
Flu season usually peaks in the United States in February and March.
Only about 1 percent of the people tested for influenza actually had it, and just 1.6 percent of patients who visited hospitals reported flu-like illness, the CDC said, below the baseline of 2.2 percent.
A child died of influenza in California, it said.
Influenza is not routinely reported to the CDC, but the agency has agreements with 1,000 health care providers in all 50 states to send in samples for testing.
Influenza typically kills 36,000 Americans and a half million people globally in an average flu season.
Flu is getting greater than normal attention this season because of the H5N1 avian influenza, which has so far infected 138 people and killed 71 in Asia. Experts fear it could mutate into a form easily transmitted by people and cause a pandemic of deadly disease.
There have been regular shortages of seasonal flu vaccine in the United States. This year the CDC says there will be enough for everyone who wants a shot to get one, although supplies have been coming in irregularly, causing temporary spot shortages.
Only about 65 percent of seniors get the recommended flu shot. The CDC has recently added small children to the list of those who should be vaccinated.
Just this week, a team reported in the New England Journal of Medicine that of 153 children killed by flu in the 2003-2004 season, nearly two-thirds were under age 5, and most had not been vaccinated.
Half were previously healthy, with no underlying conditions such as asthma.
The CDC also reported on respiratory syncytial virus or RSV, a major cause of bronchiolitis and pneumonia in young children. Anywhere between 51,000 and 82,000 people end up in the hospital with RSV every year in the United States.
It kills an estimated 4,500 children under 5 every year.
"Preliminary 2005- 2006 data suggest that the annual seasonal peak began in the South during the week ending October 15," the CDC said. There is no RSV vaccine.