The incidence of flulike illness attributed to the 2009 H1N1 virus seems to be waning both statewide and regionally.

But disease experts caution against complacency. They note that flu pandemics can come in waves, that viruses can mutate and that certain at-risk groups remain particularly vulnerable to serious complications from the H1N1 flu, also referred to as swine flu.

Some expressed concerns regarding possible misinterpretation of national publicity this week about a Harvard School of Public Health study that suggested the H1N1 flu pandemic might prove to be milder than previously feared.

Dr. Thomas Kerkering, an infectious disease expert for Carilion Clinic, said some related news coverage could mislead the public.

"For those who went through the 1918 pandemic, the current H1N1 is mild in terms of numbers of deaths -- millions [in 1918] compared to thousands," Kerkering said. "Yet with the current H1N1, we still have had many, many more children and young people die with influenza than with seasonal influenza. That's not mild."

Consistent with ongoing research, the Harvard study noted that the H1N1 flu seems to most seriously affect children from infancy to 4 years old and adults aged 18 to 64.

Marc Lipsitch, professor of epidemiology and the Harvard study's senior author, emphasized the importance of receiving the H1N1 vaccine -- especially for high-risk groups that include pregnant women, people with asthma and people with compromised immune systems.

As of Wednesday, the Virginia Department of Health reported 35 deaths statewide linked to H1N1.

Both the New River Health District and the Alleghany/Roanoke City Health Districts continue to hold school and public vaccination clinics when vaccine is available.

Like Kerkering, Dr. Jody Hershey, director of the New River district, emphasized that people should remain vigilant and get vaccinated as soon as they can -- with priority given to high-risk groups. In past pandemics, he said, waves of disease have occurred.

"Even after flu activity peaks during the current wave, it's possible that other waves of influenza activity may occur -- caused either by the 2009 H1N1 or regular seasonal flu viruses," Hershey said.

The Virginia Department of Health tracks the percentage of visits to emergency departments and urgent care facilities of people with influenzalike illnesses. According to its data, such visits spiked during the last week of October at nearly 15 percent and, at the end of last week, represented only about 3 percent of visits. Southwest Virginia's percentage seemed to spike about the same time and was down to about 3 percent, too.

Hershey observed, however, that flu activity remains widespread in Southwest Virginia and at a much higher rate "than is typical at this time of year" -- before seasonal flu traditionally begins to take hold.

The National Institutes of Health reported Monday that autopsies performed in New York City on 34 victims of H1N1 showed that the virus primarily damaged tissue in the trachea and bronchial tubes, but noted that tissue damage was seen also in the lower airway, "including deep in the lungs."

Released the same day, the Harvard study suggested that the severity of H1N1 flu during the fall and winter flu season in the United States "appears to be near the milder end."

In New River, Hershey said, the initial round of H1N1 vaccination school clinics in public and private schools, pre-K through 12th grade, should be completed by Dec. 17. He said return visits are planned for January to give the recommended second dose to children ages 9 and younger.

Millions of Americans have received the H1N1 vaccine, according to the Centers for Disease Control and Prevention. CDC reported last week that 3,783 adverse health effects had been reported nationwide through Nov. 24 that were attributed to H1N1 vaccinations.

CDC said about 95 percent of those cases were not serious. It is reviewing reports of more serious reactions, including 13 deaths, to determine whether they were related to the vaccination.

CDC said data "show that the adverse event reporting rate after 2009 H1N1 vaccination is higher than for seasonal influenza vaccination" -- but suggested that data might reflect heightened public awareness and better reporting.

Upcoming vaccination clinics

The Alleghany/Roanoke City Health Districts will hold three 2009 H1N1 vaccination clinics between Friday and Tuesday.

All are intended for priority groups, which can include emergency responders, children, pregnant women and others considered at high-risk for serious flu-related complications.

Vaccinations are free.

n When: Friday , 7 to 11 a.m.

n Where: Roanoke City Health Department

n How: By appointment only call (540) 857-7634. (Will also have about 100 walk-in slots.)

n When: Monday and Tuesday, 9 a.m. to 4 p.m.

n Where: Valley View Mall

n How: Walk-in clinic. 500 doses available.

By Duncan Adams

duncan.adams@roanoke.com 981-3324

The incidence of flu-like illness attributed to the 2009 H1N1 virus seems to be waning both statewide and regionally.

But disease experts in the region caution against complacency. They note that flu pandemics can come in waves, that viruses can mutate and that certain at-risk groups remain particularly vulnerable to serious complications from the H1N1 flu, also referred to as swine flu.

Some expressed concerns regarding possible misinterpretation of national publicity this week about a Harvard School of Public Health study that suggested the H1N1 flu pandemic might prove to be milder than previously feared.

Dr. Thomas Kerkering, an infectious disease expert for Carilion Clinic, said some related news coverage could mislead the public.

"For those who went through the 1918 pandemic, the current H1N1 is mild in terms of numbers of deaths -- millions [in 1918] compared to thousands," Kerkering said. "Yet with the current H1N1 we still have had many, many more children and young people die with influenza than with seasonal influenza. That's not mild."

Consistent with ongoing research, the Harvard study noted that the H1N1 flu seems to most seriously affect children from infancy to 4 years old and adults aged 18 to 64.

Marc Lipsitch, professor of epidemiology and the Harvard study's senior author, emphasized the importance of receiving the H1N1 vaccine -- especially for high-risk groups that include, but are not limited to: pregnant women, people with asthma and people with compromised immune systems.

As of Wednesday, the Virginia Department of Health reported 35 deaths statewide linked to H1N1. Three victims have been children. All but one, a child, had underlying medical conditions.

Both the New River Health District and the Alleghany/Roanoke City Health Districts continue to hold school and public vaccination clinics when vaccine is available.

Like Kerkering, Dr. Jody Hershey, director of the New River district, emphasized that people should remain vigilant and get vaccinated as soon as they can -- with priority given to high-risk groups. In past pandemics, he said, waves of disease have occurred.

"Even after flu activity peaks during the current wave, it's possible that other waves of influenza activity may occur -- caused either by the 2009 H1N1 or regular seasonal flu viruses," Hershey said.

And, he said, flu viruses can mutate quickly and become more virulent.

VDH tracks the percentage of visits to emergency departments and urgent care facilities of people with influenza-like illnesses. According to its data, such visits spiked during the last week of October at nearly 15 percent and, at the end of last week, represented only about 3 percent of visits. Southwest Virginia's percentage seemed to spike about the same time and was down to about 3 percent too.

Hershey observed, however, that flu activity remains widespread in Southwest Virginia and at a much higher rate "than is typical at this time of year" -- before seasonal flu traditionally begins to take hold.

"Vaccination remains the very best way to guard against future deaths and morbidity," he said. The word "morbidity" can be defined as the incidence of a particular disease.

The National Institutes of Health reported Monday that autopsies performed in New York City on 34 victims of H1N1 showed that the virus primarily damaged tissue in the trachea and bronchial tubes but noted that tissue damage was seen also in the lower airway, "including deep in the lungs."

Released the same day, the Harvard study suggested that the severity of H1N1 flu during the fall and winter flu season in the U.S. "appears to be near the milder end."

In New River, Hershey said the initial round of H1N1 vaccination school clinics in public and private schools, pre-K through 12th grade, should be completed by Dec. 17. He said return visits are planned for January to give the recommended second dose to children 9 years old and younger.

Millions of Americans have received the H1N1 vaccine, according to the Centers for Disease Control. CDC reported last week that 3,783 adverse health affects had been reported nationwide through Nov. 24 that were attributed to H1N1 vaccinations. CDC said about 95 percent of those cases were not serious, including such complaints as soreness at the injection site. It is reviewing reports of more serious reactions, including 13 deaths, to determine whether they were related to the vaccination.

CDC said data "show that the adverse event reporting rate after 2009 H1N1 vaccination is higher than for seasonal influenza vaccination" -- but suggested that data might reflect heightened public awareness and better reporting.

Most experts have said people face a much greater risk from the H1N1 flu than from receiving the vaccine.