Posts Tagged ‘H1N1 virus’

The 1918 flu virus and its descendants: Part 2 Rediscovering the culprit

Sunday, May 13th, 2012

many other major pandemics were associated with rodents, but not the 1918 flu

I re-read my last post a day after writing it and amended the first line, since I found it misleading. It was the worst flu pandemic ever, but I knew that smallpox, the Black Plague, AIDS, malaria and perhaps even typhus each have caused nearly as many or even more deaths over a period of years. I eventually found a rather strange, non-medical website with the "7 Worst Killer Plagues in history," and confirmed my belief that no other bacteria or virus had wreaked as much havoc in brief span of time as the 1918-1919 H1N1 influenza virus.

I wanted to find out what happened to that highly pathogenic organism and, after searching the web, realized the PBS article on the "Spanish flu" was a good place to start. It mentions that the influenza virus was not identified until 1933 and that the actual genetic identity of the particular strain involved in that pandemic (as opposed to the basic type...H1N1) was not identified for many years. The influenza virus responsible for the 1918-1919 pandemic has had many descendants, none as deadly as their ancestor.

In 1950, Johan V Hultin, a graduate student starting his doctoral studies in microbiology, got a clue from a visiting professor who suggested hunting for the virus in bodies buried 32 years prior in the permafrost of the Arctic. Hultin and his faculty advisor traveled to Alaska where flu among the Inuits had been especially deadly with 50 to 100% death rates in five villages.

early days in the Far North

Gold miners, under contract with the Territorial government, had served as grave diggers in 1918-1919 and tissue samples were recovered from four bodies exhumed in 1951. Pathology slides fit with viral lung damage and, in some cases, secondary bacterial pneumonia. But tissue cultures from the samples did not cause disease in ferrets and no influenza virus was recovered.

It wasn't until 1995 that science had advanced enough to for researchers to start the work necessary to identify the virus's unique features. Jeffrey Taubenberger, a molecular pathologist then working at the Armed Forces Institute of Pathology (AFIP), began a ten-plus-year-long project starting with autopsy tissues from the time of the pandemic that had been preserved in the National Tissue Repository. His project was stimulated by a paper published in the journal Science in February, 1995, in which preserved tissue samples from the famous British scientist John Dalton (often called the father of modern atomic theory) were examined. Dalton was color-blind and had donated his eyes at his death in 1844 to determine the cause of the defect; his DNA was studied 150 years later and the resultant publication gave Taubenberger the impetus to do the same with the flu virus.

Hultin read the first paper from Taubenberger's group, wrote to him and eventually went back to Alaska to exhume more flu victims. One was an obese woman whose lungs had the findings of acute viral infection. Samples of these permafrost-preserved tissue had RNA incredibly similar to those obtained from the AFIP National Tissue repository.

And so began an amazing chapter in the history of virology.

The 1918 flu and its descendants: part 1

Friday, May 11th, 2012

In some years this sign should be in red

The worst flu pandemic of all time began near the end of World War I, in the fall of 1918. It killed, in the next year, somewhere between 20 and 50 million people across the globe.  The comparison to WW I deaths, eight and a half million from all countries involved, is striking.

There had been major influenza pandemics before and since, some severe and some relatively mild. The term itself conventionally refers to a worldwide outbreak of an infectious disease with some adults in every continent (except Antarctica) involved, but doesn't imply how lethal the illness is.  For example the H1N1 "swine flu" pandemic in 2009-2010 involved 74 countries, but the death rate was relatively low.

Stanford University has a superb description of the so-called Spanish flu online. Usually flu kills the very young and the very old more than young adults; this time was different with far more deaths between the ages of 20 and 40 (some say 20-50 and others 15 to 34) than in the typical flu season. The influenza-related death rate, normally about 0.1%, has been estimated at 2.5 to 3% and may have been even higher. A fifth to a third of everyone alive at the time caught the virus, so half a billion victims may have been inflicted.

For Americans, including soldiers, the end of the war was near, but over 40,000 servicemen and nearly two-thirds of a million back home would die of this modern plague.

The precise origin of the disease is unclear; swine were affected in a nearly simultaneous fashion, but have not been blamed for the human ailment. The war itself and its resultant transportation of large numbers of troops, could have facilitated its spread globally. A first wave of the infection struck American army encampments in the United States, but was comparatively mild, at least when contrasted to the second and third outbreaks later in 1918 and then in 1919.

He was at risk as well

Public health measures were widely instituted, but the actual effectiveness of quarantine, gauze face masks, limited school closures and banning of public events is unknown.

In the midst of what for many was a typical flu infection, some developed a highly virulent form of the disease, with a strikingly abrupt onset, fever, exhaustion and rapid progression to pulmonary complications and death.

Many cases developed secondary bacterial infections and one species of bacteria was initially blamed for the disease. Then two French scientists reported a filter-passing virus in the British Medical Journal in November 1918. They used filtration to remove bacteria from the sputum coughed up by a flu patient and then injected the remaining fluid into the the eyes and noses of two monkeys. After their primate subjects were noted to have fevers, a human volunteer was given a subcutaneous injection of the same filtrate. He was the only person in their laboratory to develop the flu.

The extraordinary mortality rate of the 1918 influenza is shown on a graph plotting deaths in America from a variety of common infectious diseases over the years from 1900 to 1970. Another way to gauge the impact of the pandemic is to note that average life expectancy in the United States fell by ten years for that period.

And yet the incidence of influenza ebbed and since 1920 we've returned to the normal cycle of seasonal flu, intermittent epidemics and occasional pandemics, none as severe and deadly as the Great Flu of 1918-1919.