A fourth person has died of swine flu in Maryland - but unlike previous deaths in the state, the person did not appear to also have an underlying medical problem, health officials said Friday.
Officials gave few details on the death, saying only that the person was an adult from the Eastern Shore with no "immediately apparent underlying medical condition or risk factors."
State health officials said the death of someone without pre-existing illness should serve as a reminder to the public of how serious this flu, known as H1N1, can be - even in otherwise healthy people.
"We are saddened to report yet another death that has been associated with the novel H1N1 influenza," said John M. Colmers, Maryland's health secretary. "More H1N1 flu-related deaths are expected, as we would normally see with seasonal flu. While we wait for the development and delivery of a vaccine, everyone should remain vigilant and take precautions to protect themselves and their loved ones."
While not common, it's not unheard of for healthy people to die of the flu - either this new swine flu or the seasonal variety, said Andrew Pekosz, a professor of microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health. "A certain number of healthy people will succumb to the flu," he said.
Since the outbreak this spring, 302 people have died nationwide of the virus, according to the Centers for Disease Control and Prevention. Of the 151 people whose deaths the CDC has studied, 86 percent were at higher risk because they had some underlying medical issue - including people with compromised immune systems, chronic diseases like asthma and even obesity.
While the virus has been described as "mild," it appears to be reacting differently in people, causing a wide range of problems, said Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases.
"We've seen people with high fever and cough and respiratory illness and really not able to do much more than four or five days," she said. "Then we've seen people who have difficulty breathing, severe respiratory failure and need to be in intensive care unit for weeks. So I think there's really a spectrum."
Infectious disease experts have been concerned that the virus could mutate into a deadlier strain this fall, and Pekosz said experts will be closely examining the deaths of healthy people to determine whether the virus they died from has become more lethal.
Some 36,000 people are killed by seasonal flu each year in the United States. But Pekosz noted that those deaths happen in a nation with widespread vaccinations, with many people who have antibodies against influenza to protect them from the disease.
"If this one emerges like a seasonal flu, the number of people who could potentially be infected will be much larger than what we will have in a normal flu season," he said. "Since there is very little pre-existing immunity, vaccines are going to be an important way to limit the large number of cases that will happen."
Earlier this week, the government announced it would begin testing two H1N1 vaccines on adults and children at eight centers nationwide, including the University of Maryland's Center for Vaccine Development. It is the start of what could be a mass vaccination campaign to start in mid-October.
Meanwhile, yesterday, the CDC strengthened its recommendation that all children aged 6 months to 18 years get vaccinated against seasonal flu. In previous years, the agency has only encouraged the shots.
Maryland has 766 documented cases of the new flu virus, but officials say that figure is likely a fraction of the total cases. Most people who become ill with flulike symptoms aren't tested and recover within a week, much like seasonal flu.