In the Canadian study, about 30% to 40% of the patients had lung disease, were obese, or had high blood pressure, a history of smoking, or diabetes. Overall, 14.3% of 168 critically ill people with confirmed or suspected H1N1 died within 28 days.
The mortality rate in the Mexican study was strikingly higher. In Mexico City, where the H1N1 pandemic was first reported, 41.4% of 58 critically ill people died within 60 days of developing the flu.
Those people who died from H1N1 got sicker earlier in the course of their illness, had extremely low levels of oxygen in their blood, and had multiple organ failure. Their average age was 44 years old, and 54 of 58 patients needed mechanical ventilation. Other signs of more severe H1N1 included fever and severe trouble breathing.
In the Canadian study (in which the average age was 21.4), the critically ill tended to be hospitalized within four days of developing flu symptoms, and there was about a one-day lapse between hospital admission to intensive care unit (ICU) admission. As in the Mexico City study, younger patients with low blood oxygen and multisystem organ failure were hardest hit. What’s more, the critically ill tended to require mechanical ventilation and rescue therapies to aid in breathing.
In both countries, the H1N1 outbreak lasted about three months.
“It is not clear of hospitals’ need to invest in this ECMO technology because this has not proven very successful in other respiratory illnesses,” says Dr. Schachter. “We do know that treating H1N1 with antivirals such as Tamiflu (oseltamivir) and Relenza (zanamivir) did help improve mortality.”
The most important message is that children should get the H1N1 vaccination, which is safe, he says.
“The technology for making swine flu vaccine is no different than that used to make the regular flu vaccine, so in principle, there should be no differences in terms of safety,” he explains. “Recent surveys have shown that Americans are iffy about whether they will let their children receive this novel vaccine.”
James B. McAuley, MD, the director of Pediatric Infectious Diseases at the Rush University Medical Center, in Chicago, notes that the studies focused on the sickest of the sick patients.
“The mortality rate can be high for a small subset of people, but the overall death rate is closer to seasonal flu than the severe acute respiratory syndrome (SARS) outbreak of 2003,” he says. “This is a serious flu and there is mortality, but it is about the same as with the seasonal flu—maybe a little worse.”
As to why younger people seem to be hit hardest, the current school of thought is that perhaps a similar virus circulated 50 or 60 years ago, so older people could have immunity to H1N1.
Dr. McAuley’s advice? “Definitely get the vaccine,” he says. (He says his own children have already received the H1N1 vaccination.)
The editorialists write that the burden is on the public health system to heed the warnings in the new studies and prepare for the coming flu season: “Any deaths from 2009 influenza A(H1N1) will be regrettable, but those that result from insufficient planning and inadequate preparation will be especially tragic.” Such planning should include widespread availability of antivirals, antibiotics, and mechanical ventilation systems.
