Swine flu abates, but experts urge preparedness

Erin Allday, Chronicle Staff Writer

Friday, December 4, 2009

The swine flu is receding in the Bay Area and nationwide, and the worst of the pandemic may be over, but public health experts say it's too early for people to let their guard down.

The number of hospitalizations and deaths from the swine flu probably peaked at the end of October or early November, say infectious disease experts, but the virus is still pervasive in many regions of the United States, and many more people are sick with the flu than is typical for this time of year.

"Although the flu might be slightly decreasing both in the state and nationally, it's still very much present in our communities," said Gil Chavez, deputy director of the center for infectious diseases with the California Department of Public Health, in a media briefing Thursday. "We cannot turn our backs and be complacent. We need to be vigilant."

The best protective measure to prevent the spread of the flu is vaccination, but the swine flu vaccine is still in short supply. Shipments are picking up speed, but most communities have nowhere near the amount of vaccine they had expected to have by now, and no clear idea of when they will have enough to offer it to everyone who wants it.

Since the virus - a form of influenza Type A, subtype H1N1 - was first identified in the United States in April, the swine flu has infected at least 30 million Americans and killed about 4,000, according to the Centers for Disease Control and Prevention.

Third wave coming?

There already have been two waves of flu activity in the United States. The first one started in late spring and early summer, followed by the second wave, which picked up in September when children went back to school.

No one, not even those who study influenza for a living, knows whether there will be a third wave and, if so, how serious it would be. The virus is notoriously unpredictable, they say, and even looking at previous pandemics offers few clues as to what will happen - partly because technology and modern living, including air travel, have changed the way the flu spreads, as well as how it is treated and prevented.

"We're really in the realm of speculation," said Dr. Larry Drew, head of the UCSF virology lab, which has monitored cases of swine flu in San Francisco. "What is unclear to me is when will swine flu return, if it returns?"

One concern is that the H1N1 virus will mutate, say infectious disease experts. In a handful of instances worldwide, that has already happened and the virus became resistant to some antiviral treatments or caused more severe illness in people than would have been expected.

Those mutations, some of which have occurred in the United States, have yet to become widespread and aren't alarming public health experts. "But they're sort of cautionary notes, that we still have to be vigilant," said Dr. Stephen Parodi, chief of infectious disease for Kaiser Permanente Northern California.

And now seasonal flu

And in just a few weeks, the swine flu may not be the only virus to worry about. People typically start getting sick with seasonal flu at the end of December or in early January. But infectious disease experts say it's impossible to predict what this year's flu season will look like.

Regular seasonal flu may start to circulate in a few weeks and replace swine flu as the dominant strain. The swine flu could pick up speed again, so that multiple strains of influenza would become widespread at the same time. Or there may not be much flu at all during the typical peak months.

"We're getting to the time of year when we're used to seeing a lot of flu, so if we see it, that'll just be the norm for us. We'll be prepared," said Dr. Susan Fernyak, director of communicable disease control and prevention at the San Francisco Department of Public Health. "And if we don't get a lot of flu, that's going to be a gift."

Fernyak and other public health experts said it is still important that people get vaccinated against both the swine flu virus and the seasonal flu.

To that end, several Bay Area public health departments will be holding mass vaccination clinics this month, most of them focusing on the swine flu vaccine. At the same time, the state is launching a billboard advertising campaign to encourage people to get vaccinated.

Limited supply

But supply of the vaccine is still frustratingly limited, according to public health experts. State health officials say deliveries are speeding up and that most of the vaccine is going to private providers for now.

In some communities, including San Francisco, the burden of providing the vaccine is falling on public health clinics. Fernyak said the city was supposed to have 100,000 doses of vaccine by mid-October, but had only reached that level last week. Another 100,000 doses are on the way, she said, and it all could arrive anywhere from three weeks to two months from now.

"We get hundreds of calls every day" from people wanting the vaccine, Fernyak said. "It's been really hard to say there's no vaccine in the city."

Flu vaccine

Bay Area public health departments will hold several swine flu vaccine clinics over the next three weeks. At most clinics, the vaccine will be available to county residents who fall into the following priority groups:

-- Pregnant women.

-- People who live with or care for infants under 6 months old.

-- Health care and emergency medical workers who have direct contact with patients or infectious materials.

-- Young people ages 6 months to 24 years.

-- Adults younger than 65 with chronic health problems.

E-mail Erin Allday at eallday@sfchronicle.com.