A strain of unusually dangerous influenza that strikes all age groups and has caused a sharp increase in flu deaths in Los Angeles in the past has hit the county once again, health officials reported Friday.
The influenza virus, detected in Los Angeles County last week and also reported in San Diego, was described by one health official as a variant of the deadly Hong Kong flu that struck millions throughout the world in 1968.
"This is a strain that historically has been associated with some degree of excess mortality," said Frank Sorvillo, an epidemiologist for the Los Angeles County Department of Health. "The elderly--people over 65--are in the highest risk group."
According to Sorvillo, the type of flu now showing up in California is a variant known as influenza A (H3N2), considered more potentially troublesome than other influenza strains because it strikes disproportionately at the old as well as the young.
"We're probably right at the beginning of the influenza season here locally," Sorvillo said. "In recent weeks we have had a couple of other viruses kicking around that are similar, but the actual flu season is a little later than usual. It will run about eight weeks, into late February."
Symptoms of influenza include fever up to 104 degrees, sore throat, dry cough, muscle ache, fatigue and loss of appetite, followed by chest congestion, Sorvillo said.
He urged the elderly and others suffering chronic heart and lung ailments to contact physicians at the first signs of the disease to avoid risking pneumonia and other complications.
"The thing about flu is it is preventable," Sorvillo said. "There is a very good vaccine that people can still get from their doctors. There is also a good anti-viral drug for influenza A called amantadine, which lessens the severity of the disease if given within 24 to 48 hours of the first symptoms."
Sorvillo estimated that there are 40 to 50 deaths a week during the flu season in Los Angeles from influenza and related cases of pneumonia, but he said that can increase when a flu virus similar to the H3N2 variant strikes because, unlike some forms of the flu, it is not primarily confined to age groups under 30.
"In Los Angeles County, we have about 1,000 deaths a week from all causes," Sorvillo said. "During the winter months, pneumonia and influenza stand at about 4% to 5% of the total deaths, or 40 to 50 a week. The last time that went up was the winter of 1980 and 1981, when we had a virus similar to the one we have now. There were more than 80 deaths a week then."
Both Sorvillo and Dr. Robert Murray, an epidemiologist with the infectious diseases branch of the state Department of Health Services, said it is impossible to predict how widespread this year's influenza outbreak will be.
"The season so far has been very mild and is still relatively young," Murray said. "Most of the people who have been sick so far have not had influenza. There are 100 different viruses that cause similar illness, and they have had some of those, including colds.
"The flu viruses going around the past few years have mainly affected younger persons under 30. The difference with the H3N2 strains is that they can affect people of all ages. Therefore this strain affects more older people and some are at a higher risk of dying from complications."
Murray said there have been no confirmed reports of influenza so far in any area of the state besides Los Angeles and San Diego counties.
The Centers for Disease Control in Atlanta has confirmed outbreaks of the same flu variant in nine other states in the West and Midwest.
"The flu usually goes around in pockets," Murray said. "The influenza viruses, by nature, have subtle and not so subtle changes in their makeup from year to year. If there is a really dramatic change, then you can have the great big epidemics such as the Hong Kong flu in 1968, when there was a worldwide epidemic.
"That's when the H3N2 strains first appeared. This is a variant of the Hong Kong flu, with many years of minor changes in the makeup of the virus. The primary concern is for the elderly, who should certainly check with a doctor if they get sick. People of average health under 65 generally recover without serious problems."