A primer on novel H1N1 virus, or swine flu

David Gulliver - posted 1:45 pm Thursday, July 30

With conflicting reports circulating in the media, Sarasota Health News this week interviewed state and local health experts and listened to broadcast press conferences from national experts to put together a primer on swine flu, properly called novel H1N1 virus.
Among the findings:
- Despite the alarmist tone of some reports, novel H1N1 virus has been remarkably similar to seasonal flu, for both how it spreads and how severe it can be.
- One significant difference from seasonal flu is that young adults have been far more likely to contract the virus, and it has been most severe in middle-aged adults.
- To date Sarasota County has had only one outbreak, a group of cases among students at a Ringling College summer program. The isolated cases of two Sarasota Memorial Hospital employees did not constitute an outbreak, state and local health experts said.

What is novel H1N1 virus?
It is a new flu strain that appeared in the United States in April. It has genes from flu viruses that circulate in humans and pigs, and genes from humans and birds, according to the Centers for Disease Control and Prevention.

How does it spread?
It spreads primarily the same way seasonal flu spreads: person to person, via droplets expelled when a person sneezes or coughs, said Dr. William Heymann, medical executive director of the Sarasota County Health Department and an infectious disease expert. You also can contract it by touching an object with virus particles and then touching your mouth, nose or eyes. Experts advise frequent hand-washing

How prevalent is novel H1N1 virus?
Most media reports have focused on the number of confirmed cases, but experts say those are the tip of the iceberg.
Sarasota County now has 23 confirmed cases, but there almost certainly have been hundreds in the region, Dr. Heymann said. He and his staff see that as a positive, in a way: Most cases have been mild enough that the flu sufferer did not realize it was flu, or did not feel the need to seek treatment.
Similarly, the CDC estimated two weeks ago that there have been about 1 million cases nationwide, but only about 44,000 confirmed by testing.
About 98 percent of tested cases are found to be novel H1N1, so if people have flu-like symptoms, odds are that it is what they know as swine flu. That has led doctors and hospitals to scale back on testing, which can take days, and simply treat patients for novel H1N1.

Have there been any local outbreaks of novel H1N1 virus?
Scientists differ on what “outbreak” means, but they recognize the word has a connotation beyond its textbook definition. Dr. Russell Eggert, director of the Florida Department of Health’s Division of Disease Control, offered a widely accepted standard: An outbreak is a greater-than-expected number of cases in a certain population and with a common link.
To date, Sarasota County has had just one outbreak, where several students at a Ringling College summer program developed symptoms and four tested positive for novel H1N1. To date, the virus has not spread to any other students or college employees.
Two Sarasota Memorial Hospital employees tested positive for the virus. The employees did not work together and appeared to have contracted it separately, and to date it has not spread to patients.
Media reports called it a “potential outbreak,” but Dr. Eggert said only the Ringling case met that standard. Sarasota County Epidemiologist Scott Pritchard agreed. “ A hospital experiencing two random people with the illness, who came in on two different days, doesn’t represent an outbreak.”
No one should be surprised if health care workers contract a flu virus, Dr. Heymann said, and it should not deter anyone from seeking treatment at a hospital or other location.

How dangerous is novel H1N1virus?
Again, experts point to it as being similar to the seasonal flu that spreads every winter. The severity varies, from mild discomfort to being incapacitated for a week to hospitalization and, in rare cases, death. Seasonal flu kills about 36,000 people nationwide every year, according to the CDC.
The same is true for novel H1N1. “The majority of cases are uneventful, but there are some cases where we are seeing deaths,” Dr. Eggert said.
While it’s tempting to calculate mortality rates from the published numbers of confirmations and deaths, it also would be wildly incorrect, experts say.
Most cases go uncounted, Drs. Heymann and Eggert noted. Disease surveillance systems, like an automated symptom tracker based in emergency rooms and developed after 9/11, indicate far more cases than are confirmed by tests. And even those systems don’t capture every case.
If CDC’s estimate of 1 million cases is correct, the 302 deaths nationwide as of July 21 would mean about three cases in 10,000 are fatal. But neither the cases nor deaths figure is remotely precise.
The Florida Department of Health, tracking only that iceberg-tip of severe cases confirmed by testing, found about 12 percent led to hospitalization. But the hospitalization percentage of all cases, confirmed, probable, reported and unreported, would be far less.

Who is most at risk?
This is where novel H1N1 breaks from traditional seasonal flu.
While seasonal flu usually hits the elderly hardest, this new flu has flipped the demographic curve 180 degrees. In Florida, 66 percent of confirmed novel H1N1 cases -- almost two-thirds -- have been in people 24 and younger. About 11 percent of all cases are in children 4 and younger. National figures are similar.
The reason is that older people may have some partial immunity from flu strains that circulated decades ago, Drs. Eggert and Heymann said.
Two other groups may be more likely to have severe cases. “People in their 40s and 50s are more likely to have some underlying chronic condition that makes them more vulnerable,” Dr. Eggert said.
Pregnant women also seem to be at higher risk of developing a severe case, according to a study published Wednesday in British medical journal The Lancet.
Researchers looked at a small sample of cases in the United States. They found pregnant women who had contracted the virus were much more likely to be admitted to the hospital than novel H1N1 patients in general. Experts say that may be because pregnancy suppresses the body’s immune response, making the mothers-to-be more vulnerable.

When will there be a vaccine, and who will be able to receive it?
Also on Wednesday, a CDC committee announced plans to prioritize vaccinations for novel H1N1. Given the Lancet article, it’s little surprise that pregnant women are in the group recommended to have first access to the vaccine.
CDC said there would be some 120 million doses available by mid-October, about one-third of them ready by September if needed. They expect manufacturers to produce 80 million doses per month after that.
The other priority groups are health and emergency medical workers, people ages 4 to 24, people 25 to 64 with underlying chronic health problems, and people who care for infants under 6 months, because the infants cannot be vaccinated.
That population group is about 159 million people and outnumbers the projected doses, especially if people need two doses, as expected.
But Dr. Anne Schuchat, director of CDC’s National Center For Immunization and Respiratory Diseases, said that typically only 20 to 50 percent of target groups ever get the seasonal flu vaccine. And the panel developed a two-tier approach, with a smaller group -- just pregnant women, health workers and infant caretakers -- first in line for the shot.
How it will all work out is still undecided. The panel’s recommendation goes to CDC leadership, and that ruling will go out to state and local health departments, who will determine how to execute the plan.
CDC and health experts also strongly recommend that people also get a seasonal flu vaccine, which will require a separate shot and possibly a separate doctor visit. They are worried that confusion over the two vaccines will leave some people susceptible to one flu virus or the other.

What can we expect by fall?
Experts agree that schools reopening will make it easier for the virus to spread, and cooler weather is believed to increase transmission. "We are expecting a resurgence of H1N1 virus in the fall and winter months," Dr. Eggert said. But they are unsure whether closing schools would make a significant difference. If children aren’t in school, they may congregate someplace else, like parks or shopping malls, where they also could transfer the virus, Pritchard said.
In last week’s media briefing, CDC’s Dr. Schuchat said in the spring flareup of novel H1N1, some communities saw “attack rates” of 6 to 8 percent of people reporting flu-like symptoms. She said this winter, that rate could double or triple. But experts say there still are too many unknowns -- most importantly, how effective the vaccination campaign will be. For now, they simply urge caution and common sense. "We don't want people to panic about the severity of the disease, but we don't want them to be complacent, either," Dr. Eggert said.