WASHINGTON, D.C. (Reuters) – Autopsies on people who have died from the new pandemic H1N1 flu show this virus is different from seasonal influenza, even if it has not yet caused more deaths, experts say.
Americans who died from H1N1 had infections deep in their lungs, Dr. Sherif Zaki of the U.S. Centres for Disease Control and Prevention told a meeting of flu experts, including damage to the alveoli, the structures in the lung that deliver oxygen to the blood.
This in turn caused what is known as acute respiratory distress syndrome, an often fatal development that leaves patients gasping for breath.
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The World Health Organization has confirmed 3,205 deaths globally from H1N1 but experts agree all estimates of the extent of the pandemic are grossly understated because so few patients are tested.
Seasonal flu kills about 250,000 to 500,000 people each year globally, according to the WHO, but not in the same way as H1N1, which frequently causes severe disease in young adults and children.
“It is very rarely you see what we call diffuse alveolar damage in fatal seasonal influenza,” Zaki told a meeting sponsored by the U.S. Institute of Medicine, which advises government on health matters.
Seasonal flu causes bronchitis and other upper respiratory disease. But Zaki, the chief infectious disease pathologist at CDC, said the new virus had burrowed into the lungs of the 90 bodies he examined and they had huge amounts of the virus in their blood.
“This is almost exactly what we see with avian flu,” Zaki said. “This looks like avian flu on steroids.”
Lungs hard hit
Dr. Yoshi Kawaoka of the University of Wisconsin said tests in monkeys showed the virus lives and replicates 1,000-fold better in the lungs than does seasonal flu.
He said the drug, Tamiflu, lowered the viral load of virus in the lungs just enough to help the body fight back.
Experimental flu drugs lower it even more, Kawaoka said.
Zaki said 90 percent of the fatalities he looked at had some condition that would predispose them to serious disease. They had a median age of 38 and one victim was a two-month-old infant who died within a day of getting sick. About 46 percent were obese, many had fatty liver disease, 27 percent had heart disease and 22 percent had asthma, he said.
Dr. Guillermo Ruiz-Palacios of Mexico’s National Institute of Medical Sciences and Nutrition said many Mexican patients with severe disease were also obese. In addition, patients came in late for treatment and many were infected with a second common virus, called parainfluenza virus.
Fewer than a third of the U.S. deaths, 29 percent, had a secondary bacterial infection, usually streptococcus pneumoniae, Zaki said.
Ruiz-Palacios also said the new virus can be found in the urine and feces of patients, something that may affect how it spreads.
