liveonearth (liveonearth) wrote,

Flu: The Book and some thoughts

Last night I *finally* finished reading this book: Flu; The Story of the Great Influenza Pandemic of 1918 and the Search for the Virus That Caused It. The last third of the book was less interesting to me than the first part. It followed the stories of many assorted researchers who were trying to recover live virus from bits of frozen bodies that had been buried in the permafrost layer of the northern tundra, or bits of viral genes from samples of lung tissue that had been saved in blocks of parafin by military doctors.

There was a long section in the middle that discussed the history of the 1976 attempt to immunize all US citizens against a swine flu that was linked to the 1918 flu by the fact that people who survived the 1918 human version have antibodies to swine flu, even if they have never been around pigs. The swine flu immunization campaign was a disaster on President Ford's watch. It illuminated the difficulties inherent in any large immunization program. Most simply it must be noted that if you vaccinate a great number of people, fate will have it that at least a few of them will soon after die or have some sort of medical issue. It is normal in human thinking to ascribe causality to things that occur in temporal proximity. If someone gets sick or dies soon after being vaccinated, people will believe that the vaccine caused the death or difficulty, when in fact it was unrelated.

I was particularly interestesd in the theories and conjecture about where, how and why flus get started. It appears that every pandemic flu on record has started in southern China, in Canton. Robert Webster (of St Jude Children's Research Hospital in Memphis) and Dr. Kennedy Shortridge of the University of Hong Kong developed a theory about the origin of flu that sounds reasonable to me, so I'll try to communicate it here.

In southern China, people and pigs and fowl live in close proximity (and high population density). Viruses and bacteria can be exchanged among individuals and species with relative ease. Birds such as ducks, chickens and geese, may show no symptoms while they carry flu viruses inside cells of their intestines. Sometimes, however, they may also get sick. Ducks are especially suspect as viral vectors because of they are used by Chinese farmers to keep rice paddies free of weeds and pests--and because their usual quarters are adjacent to the pig pens.

The H and N refer to hemagglutinin and neuraminidase proteins that are present on all flus. Hemagluttinin incidentally makes red blood cells clump (hence the name), but it is used by the viurus to get into a cell. Neuraminidase is used by new virus babies to bust out of a cell to infect new cells. New versions are numbered in order of appearance in human flus. We can't have immunity to a totally new H or N protein, because it didn't exist before for our immune systems to remember. The 1946 flu was H1N1. The 1957 "Asian" flu (H2N2) and the 1968 "Hong Kong" (H3N2) flu both caused pandemics, and both involved new virus strains that seem to have come *indirectly* from birds in southern China. Before then we weren't able to test viral genetics, but the observation was the same that China is the flu epicenter of the world.

It is thought that a bird flu cannot directly sicken a human, because it won't have the right enzymes to attack the cells of a human lung. It appears that the flu needs to incubate and exchange genes with other viruses while in another species. Pigs seem to be the common intermediate for flu viruses between humans and birds. Imagine that a poor pig gets infected with bird and human flu viruses at the same time, and the viruses exchange genes such that a new hybrid flu is formed that has some genes of each. Voila! A new pandemic in the making.

Apparently the 1918 flu was no big deal in southern China. No mass graves there. Not a blip. The best guess is that people there had been passing that flu around for some time, and were immune, but that while it was being passed around it evolved such that it was highly transmissible among humans.

In 1997 a boy in Hong Kong died of a flu that turned out to be an H5N1, never before seen in humans. Scientists were horrified, because it appeared that the virus had come directly from a bird, and not via swine. It also appeared that no one got the flu from the boy. Hong Kong gets 80% of its chickens from China. In late December it was confirmed that the birds were sickening from the new virus. It was feared that if a human could get this flu, the genetics could rearrange in a human such that human to human transmission would become possible and there would be a new pandemic. Public health officials decided to require that all possibly infectious birds be killed, and on December 29, 770,000 birds were killed. By the end over 1.2 million chickens had been killed and incinerated. After that the birds were tested for the virus and none were infected with the H5N1. But I am sure that it is out there somewhere, still.

Thinking again about how this will affect my medical practice...........will it? I still believe that if a person has a healthy immune system, it is better to be exposed than not to be exposed, because then you build immunity. But if it is that one particularly lethal strain, the cost could be great. Still working on this question....
Tags: biochemistry, birds, books, china, disease, flu, history, public health, vaccines, viruses

  • QotD: I Think

    I think, therefore I am... confused. --Benjamin Hoff in The Tao of Pooh

  • QotD: the cost of loving

    “If you’ve got a heart at all, someday it will kill you.” —Rita Dove, poet

  • QotD: If you don't

    "If you don't do it this year, you will be one year older when you do." -Warren Miller

  • Post a new comment


    Comments allowed for friends only

    Anonymous comments are disabled in this journal

    default userpic

    Your reply will be screened

    Your IP address will be recorded