Pneumonia, Susceptibility of Young Among Traits of Swine Flu
Saturday, October 17, 2009
As swine flu continues to spread around the globe, a clearer and in some ways more unnerving picture of the most serious cases has started to emerge, indicating that the virus could pose a greater threat to some young, otherwise vibrant people.
The virus can cause life-threatening viral pneumonia much more commonly than the typical flu, prompting the World Health Organization on Friday to warn hospitals to prepare for a possible wave of very sick patients and to urge doctors to treat suspected cases quickly with antiviral drugs.
Experts stress that most people who get the H1N1 virus either never get sick or recover easily. But some young adults, possibly especially women, are falling seriously ill at an unexpectedly rapid pace and are showing up in intensive care units and dying in unusually high numbers, they say.
Although why a minority of patients become so sick remains a mystery, new research indicates that H1N1 is different from typical seasonal flu viruses in crucial ways -- most notably in its ability to penetrate deep into the lungs and cause viral pneumonia.
"It's not like seasonal influenza," Nikki Shindo of the World Health Organization said at the conclusion of a three-day meeting of more than 100 experts the WHO convened in Washington to review swine flu. "It can cause very severe disease in previously healthy young adults."
Meanwhile, the Centers for Disease Control and Prevention reported Friday that vaccine production was proceeding more slowly than hoped. Officials had predicted that about 40 million doses would be available by the end of October, but that projection will probably fall short by about 10 million to 12 million doses, said Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases.
"Eventually, anyone who wants to be vaccinated will be able to be, but the next couple of weeks will continue to be a slow start," she said. So far, 11.4 million doses have become available and states have ordered about 8 million doses, but the vaccine will not become available in large amounts until November, she said.
The WHO's warning came as U.S. health officials reported that the number of states reporting widespread flu activity was up to 41, including Maryland and Virginia, and that the death toll among children had climbed to 86. Maryland has reported 10 deaths and Virginia health officials say eight people, including one child, have died. There have been no reports of deaths among District residents.
So far, the virus does not seem to sicken or kill people more often than the typical flu. But the pattern of people getting seriously ill is far different than in typical flu seasons. The elderly, who are usually most vulnerable, are generally spared; children, teenagers, pregnant women and young adults are the most common victims.
Officials have been closely monitoring the virus for signs it has mutated into a more dangerous form, and they have also been testing animals for the virus because of fears that infected livestock could cause more-lethal mutations.
Federal agriculture officials said Friday that pigs from the Minnesota State Fair had tested positive for H1N1, which would make them the first documented pig infections in the United States, if follow-up tests confirm the results. But there are no signs that the pigs were sick or that the animals had infected any humans. Children staying near the fair had gotten the virus, but there was no sign they were infected by the pigs.
Seasonal flu viruses tend to infect primarily the upper respiratory system. But recent animal studies and autopsies on about 100 swine flu victims show that H1N1 infects both the upper respiratory tract, which makes it relatively easy to transmit, and also the lungs, which is more similar to the avian flu virus that has been circulating in Asia.
"It's like the avian flu on steroids," said Sherif Zaki, chief of Infectious Disease Pathology at the CDC. He noted that unusually large concentrations of the swine flu virus have been found in the lungs of victims: "It really is a new beast, so to speak."
About a third of patients who required intensive care had bacterial pneumonia, but H1N1's proclivity to infect lung cells makes it more likely than seasonal flu to cause viral pneumonia, which can lead to life-threatening lung damage.
"Remarkably different is this small subset of patients that presents very severe viral pneumonia," Shindo said.
One of those patients was Karen Ann Hays of Sacramento, Calif., an otherwise healthy nurse whose hobby was tackling grueling triathlons. Despite desperate measures to keep her alive, Hays, 51, died in July within days of coming down with swine flu.
"I have seen more cases like this in the last three months than I have in the last 30 years," said Peter Murphy, director of intensive care at the Mercy San Juan Medical Center in Carmichael, Calif., who tried to save Hays.
Although it remains unclear how frequently the virus makes people seriously ill, recent reports from Mexico, Canada, the United States, Australia and New Zealand indicate that perhaps 1 percent of patients who get infected require hospitalization. Between 12 to 30 percent of those hospitalized need intensive care, and 15 to 40 percent of those in intensive care die.
While about two-thirds of U.S. patients who were hospitalized in the spring had other medical conditions, the CDC reported this week that an analysis of more than 1,400 hospitalized victims found perhaps half had no serious health problems.
About one-third of those around the world who have died or became seriously ill from swine flu appear to have been vulnerable because they had heart or lung disease, chronic kidney problems, or other ailments that usually put people at risk. But others had conditions that many may not immediately associate with frailness, such as mild asthma, high blood pressure, high cholesterol and obesity.
"Many of these people look just like you or me," said Anand Kumar, an associate professor of critical care and infectious disease at the University of Manitoba in Winnipeg, Canada, which was hit hard by the pandemic's first wave last spring.
There appears to be no way to predict with certainty who may suffer serious, life-threatening complications, since some victims have had no other health problems.
For instance, Stacey Hernandez Speegle, 30, of Madison, Calif., who died in July, "was in great shape. She was on the softball team. She had two young children. She was renovating her house," said her mother, Tamara Brooks. "It's just so hard to believe."
Although it has been well publicized that pregnant women appear to be at increased risk, some evidence has started to suggest that being female may itself be a risk factor, for reasons that remain unclear.
"There's no question that women, and particularly young women, are getting hit disproportionately," said Kumar. He noted that women tend to have more fat tissue, which can help stimulate a dangerous inflammatory response to infections.
And some of those who develop serious illness deteriorate soon after starting to feel ill. They require oxygen masks, ventilator machines to pump oxygen into their lungs to keep them alive, and drastic, often rarely used measures to try to save them within days of the first fever, ache or cough.
"The rapidity of it is striking," said Andrew R. Davies, deputy director of intensive care at Alfred Hospital in Melbourne, Australia.
Some of the cases in Australia and New Zealand were so severe that doctors resorted to a much more aggressive, less commonly used treatment known as extracorporeal membrane oxygenation (ECMO). It involves siphoning patients' blood into a machine to remove carbon dioxide and then infuse it with oxygen before returning it to their bodies.
"It's quite an extreme form of treatment," said Steve Webb, a clinical associate professor at the Royal Perth Hospital in Australia.
Other doctors have tried administering nitric oxide and putting patients in a bed that turns them upside down to help their lungs work better. "Our back was against the wall," Murphy said, adding that after the deaths of patients such as Hays his hospital is working to make ECMO available.
"It's very difficult to get this double-barreled message out that: 'Yes, most cases are mild, but in a small percentage of cases these cases are disastrous,' " Vanderbilt University's William Schaffner said. "But the message is: Don't underestimate H1N1."
Of the at least 86 Americans younger than 18 who have died from H1N1, 11 deaths were reported in the past week. About half of the deaths in the past month were among teenagers, Schuchat said. Since Aug. 30, 43 pediatric deaths have been reported, including three in those younger than age 2, five among those ages 2 to 4, 16 in those ages 5 to 11, and 19 among those ages 12 to 17, she said.
"These are very sobering statistics," Schuchat said, noting that only about 40 or 50 children usually die during an entire flu season.
Virginia Health Commissioner Karen Remley said Friday that although the majority of H1N1 cases in the state are "mild and moderate," significant numbers have become seriously ill.
In Maryland, at least 257 people have been hospitalized with confirmed cases of H1N1 since June, health officials said.
At least 2,914 Americans have died from flu-related illnesses since the H1N1 began, the CDC said.
Staff researcher Madonna Lebling and staff writer Michael Laris contributed to this report.