Higher Human Learning

H5N1 may attack the brain

The Z+ strain of H5N1 has not only been getting better at killing other mammals like mice, pigs, and cats, it has learned to burrow deep into human lungs. The scientist who discovered the SARS virus explains how H5N1 has been mutating to better effect our death: “Unlike the normal human flu, where the virus is predominantly in the upper respiratory tract so you get a runny nose, sore throat, the H5N1 virus seems to go directly deep into the lungs so it goes down into the lung tissue and causes severe pneumonia.”⁴⁶² The director of Oxford University’s Clinical Research Unit in Ho Chi Minh City describes how shocked he was by what he was seeing. “I’ve never experienced anything like it in terms of its destructive power,” he said. “It is staggering in terms of how much lung tissue is destroyed.”⁴⁶³

H5N1 and the virus of 1918 both shared a proclivity for the lungs, but H5N1 doesn’t always stop there. It may dig deeper, invading the bloodstream to ravage other internal organs. What starts as a respiratory infection may become a whole-body infection. Researchers were surprised to find that the 1918 virus, with all its fury, had not mutated to destroy other organs. This is thought to be why H5N1 may be more than ten times more lethal than the virus that sparked the greatest medical tragedy in human history.⁴⁶⁴

As human contagious diseases go, only Ebola and untreated HIV infection are deadlier.⁴⁶⁵ But H5N1 could go airborne. In a tone one rarely finds in scholarly medical journals, Lancet, perhaps the most prestigious medical journal in the world, editorialized, “In view of the mortality of human influenza associated with this strain, the prospect of a worldwide pandemic is massively frightening.”⁴⁶⁶

One of the organs H5N1 can damage, the medical world swiftly realized, is the human brain. The first case report in the New England Journal of Medicine started with the line: “In southern Vietnam, a four-year-old boy presented with severe diarrhea, followed by seizures, coma, and death.” His nine-year-old sister had died similarly two weeks earlier. She was fine one day, and dead five days later. Her brother lasted a week. The bird flu virus seemed to attack their central nervous systems, plunging them into rapidly progressing fatal comas. The Oxford investigators concluded, “These reports suggest that avian influenza A (H5N1) virus is progressively adapting to mammals and becoming more neurologically virulent.”⁴⁶⁷ “This virus is particularly nasty,” says Nancy Cox, the chief influenza scientist at the CDC. “We’ve never seen any influenza virus quite like it before.”⁴⁶⁸

Researchers weren’t sure how the virus got to the brain. They assumed it traveled there through the bloodstream where live virus has been found,⁴⁶⁹ but experimental studies showed a possible alternate route. Once inhaled, the virus may creep up the olfactory nerves used for our sense of smell, leading to direct brain invasion though the nose.⁴⁷⁰

H5N1 is like no flu virus anyone has ever seen. St. Jude’s Robert Webster describes the virus as a “wily adversary.” “Just when you start to think that you’ve understood what it can do then it pulls another one out of the bag,” Webster said. “It’s one of the most crafty of all infectious disease agents. It’s got such a repertoire of tricks.”⁴⁷¹ H5N1 is still having trouble, to date, learning how to pull off its greatest trick of all—efficient human-to-human spread.