February 2000
ATLANTA - Influenza got an early start this season, and cases were reported in every state, according to the Centers for Disease Control and Prevention (CDC).
Influenza activity was reported to be widespread in 31 states, and regional activity was reported in an additional 11 through the week of Jan. 8.
Pneumonia and influenza were responsible for 9.3% of deaths. The epidemic threshold for the same period was 7.3%. Pneumonia and influenza death rates exceeded threshold values for 14 of the last 15 weeks of 1999 and for the first week of January.
Patient visits due to influenza-like illness decreased from 6% during the final week of 1999 to 5% during the first week of January.
Although the percentage of pneumonia and influenza deaths in 122 cities was higher than usually seen, updated data from the CDC indicate that the proportion of patients seen by a sentinel network of physicians and the numbers and types of circulating influenza viruses are similar to the previous seasons. These findings suggest that this year's flu season has not been unusually severe.
Influenza activity has also affected the nation's blood supply. While the supply normally goes down over the holidays, donor activity normally picks up in January. The American Red Cross reported that 27 of its 37 blood services regions had less than a one day supply of type O blood.
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By the beginning of January,
most states were reportedly feeling the flu season's early start, including New
York. "At this time last year, we had 38 reports of outbreaks," said Claire
Pospisil, spokeswoman for the New York State Department of Health. "We're
seeing four times as many outbreaks this year if you compare it to the
information we had last year at this time."
By mid-January, 112 outbreaks were reported in hospitals and long-term care facilities throughout New York State.
Illinois has been experiencing heavy influenza activity since the end of 1999, about three weeks earlier than most years.
In Texas, where influenza activity is also widespread, the first culture-confirmed case was reported Oct. 14, 1999. There were 183 culture-confirmed cases reported as of mid-January.
In Washington, 333 cases of influenza A have been laboratory confirmed since October 1999. "It's slightly worse than last year, but not dramatically," said Steve Kelso, information officer for the Washington State Department of Health.
While people of all ages are affected, those at the extremes of age face the brunt of problems.
"It's hitting hardest in very young people and in older people," Kelso said. Eleven percent of cases have been reported in children younger than 1; 8.6% in children 10-19, 4.9% in children 5-9, 4.3% in 1-year-olds, 3.7% in 2-year-olds, 2.5% in 3-year-olds and 0.6% in 4-year-olds.
"In San Antonio, we're seeing a large number of children in preschool with influenza," said Neil P. Pascoe, RN, of the Baylor College of Medicine in Houston and influenza surveillance coordinator for the Texas Department of Health. "In other communities it's more school-age children. Children are the predominant vector for influenza, so it's not surprising to see school absenteeism increase. But it's the entire age range."
Children are often the first to get influenza in a community, said Robert Hudson, MD, of the National Flu Surveillance Network in Oklahoma City. "There's a slight delay of a week or two, and then the adults get sick."
"Most children and healthy adults recover without difficulty," said Carolyn Bridges, MD, epidemiologist at the CDC. However, "parents get very concerned when their children have a fever, and parents need to see a doctor to get an accurate diagnosis of influenza."
Several assays are available for rapid testing for influenza. Approximately 12,000 people were tested through the middle of January, Hudson said.
Not everyone needs treatment for influenza, but early treatment - within 48 hours of the onset of symptoms - may alleviate severe symptoms, and prophylaxis may prevent other family members from becoming sick.
Amantadine and rimantadine (Flumadine, Forest) have both been shown to reduce severity and duration of influenza A illness. They may also be used for prophylaxis.
Treatment should be discontinued as soon as clinically warranted, after three to five days of treatment or 24-48 hours after symptoms have disappeared.
Amantadine may be given to children older than 1. To reduce the risk of toxicity, children should not receive more than 5 mg/kg/day or a total of 150 mg/day. Children 10 or older may take 200 mg/day. Children weighing, 40,40 kg should not receive more than 5 mg/kg/day.
Rimantadine has only been recommended for prophylaxis for children, but "many pediatricians also consider rimantadine safe [for treatment] for children younger than 14 years of age," Bridges said. The recommended dose is 5 mg/kg/day for children 1-9. Children 10 and older may take 200 mg per day. Children weighing, 40 kg should not receive more than 5 mg/kg/day.
For children 12 and older, zanamivir (Relenza, Glaxo Wellcome) may also be an option. It may reduce duration of moderate or severe symptoms by one day. Zanamivir has not been demonstrated to be effective in preventing serious influenza-related complications, and it has not been approved for prophylactic use. The recommended dose is two inhalations twice daily for five days.
According to a recent Food and Drug Administration (FDA) advisory, physicians should use caution if prescribing zanamivir to patients with underlying asthma or chronic pulmonary disease. The FDA has received reports of deterioration of respiratory function following inhalation of the drug in this population. Careful monitoring, observation and supportive care should be practiced when using zanamivir in these patients.
Accurate diagnosis is especially important when considering an antiviral. The possibility of primary or concomitant bacterial infection should be considered, and antibiotics should be prescribed if bacterial infection is suspected.
"Antivirals are only for influenza," Bridges said.
The FDA has received reports of patients who initially had influenza-like symptoms whose bacterial infections progressed while they were being treated with antivirals.
Most circulating strains of influenza this season are contained in the currently available vaccine.
"The strain we're seeing is influenza A," Pospisil said. "It's a Sydney-like strain, H3N2. That's the only type of influenza we're seeing at this point. It's a good match for the vaccine this year."
The vaccine is recommended for anyone older than 6 months who is at increased risk of influenza. Health care workers and others who may be in close contact with people at high risk should also be immunized, as should pregnant women who will be beyond the first trimester during the influenza season.
Children younger than 9 should receive two doses. The vaccine may be given at the same time as other routine immunizations.
For more information:
- Winquist AG, Fukuda K, Bridges CB, et al. Neuraminidase inhibitors for treatment of influenza A and B infections. MMWR.1999;48(RR14):1-9.
- Fukuda K, Bridges CB, Brammer TL, et al. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR.1999;48(RR-04):1-28.
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