The Natural History of the Flu: My Latest Story For The NY Times

By Carl Zimmer | May 4, 2009 10:47 pm

You have to hand it to those little flu viruses–with just a few genes apiece, they can infect us humans by the millions, and we can barely keep up with their evolution. In tomorrow’s New York Times, I’ve written a natural history of the flu, looking at how influenza viruses mutate, swap genes, undergo natural selection, cross species barriers, and  adapt to new hosts. The new strain of swine flu (or perhaps more precisely, the new strain of human-and-bird-flu-viruses-swirled-up-inside-pigs-and-then-mixed-with-other-pig-viruses-that-descend-from-human-and-bird-flus-as-well) is just the latest chapter in this baroque evolutionary tale.

Comments (6)

Links to this Post

  1. The Evolution of the Flu Virus | Surprising Science | May 6, 2009
  1. synergy

    Well, you don’t need an engineering degree to break an engine. You just need to be able to throw a wrench into the works. ;)

  2. Jason

    Stop telling us that viruses evovlve! That’s just a trick of Darwin and.. uh.. uh.. intelligent design! Yes! God wants us to suffer and die! … I mean.. wait.

    Great article, sir. ;)

  3. Monkey

    I have never heard of, nor considered, the aspect of pigs being a blender of sorts for myriad viral strains. Could you eluicidate on this in a further post? What is the biology of pigs that makes them efficient at combining viruses? I bet my students would love to hear about this…viruses and bacteria get them the most excited every year (well, also the nudibranch pictures from nat geo!!)!

  4. Morgan

    Sorry, but you left yourself wide open for this one…
    http://www.partiallyclips.com/index.php?id=1112

  5. Dan

    Some facts about Influenza Viruses:

    Virus is a Latin word, meaning ‘poison’.

    A virus is more of a very well organized molecular parasite than an actual life form, such as a bacteria.

    The virus cannot grow or reproduce without a host cell. That means it needs a bird or mammal, such as humans, in order to exist and thrive.

    And the virus has the potential to completely destroy the host in the process in order to exist.

    The influenza viruses are of what are called orthomyxoviruses, which is a group or family of RNA viruses that are categorized into A, B, and C.

    The Influenza A virus is the one that historically has caused pandemics that have developed in the past.

    About eighty percent of flu cases in the U.S. are type A influenza viruses.

    Influenza vaccinations are the only available method of prevention at this time from the potentially deadly effects of influenza.

    Influenza is the virus responsible for the disease that has its name, and it is spread easily to other humans.

    This virus can be deadly to a greater degree when the virus creates a pandemic, which did happen in the United States and other parts of the world less than 100 years ago.

    Other influenza pandemics primarily have occurred in countries in Asia.

    For an influenza pandemic to occur, which means a global disease existence and presence, the virus must emerge from another species to humans without a strong immune system- as well as the ability to make more humans ill than normal due to the constant mutation of the influenza virus.

    Also, the virus must be highly contagious for a pandemic to occur.

    This particular virus that has been identified is just that.
    That pandemic caused around a half a million deaths in the United States alone.

    This event is now known as the Great Influenza Epidemic.

    Understandably there was panic among people worldwide, as the influenza virus itself was not identified until the year 1933.

    So, the mystery was rather frightening of what was happening at that time.

    The etiology for the deaths that were happening so rapidly was complete mystery to everyone.

    Clearly, at times these influenza viruses are more dangerous than others, and this was one of the strains that clearly very most toxic during that particular epidemic.

    Presently, influenza is once again a very concerning sub-microscopic infectious agent, and we are their potential hosts in order for these viruses to survive.

    The potentially deadly effects of the influenza virus is due to this virus penetrating the host, such as a human being

    Once infected and established in the host, the virus replicates within the cell of the host in the cell’s cytoplasm.

    To survive, the influenza virus targets an enzyme called polymerase, which is what directs the content of this cell to produce proteins the virus needs to exist.

    Unlike coryza, influenza expresses symptoms more severely, and usually lasts two weeks until one recovers who has the flu.

    Influenza, however, poses a danger to some with compromised immune systems, such as the chronically ill.

    So the risk is greater in such populations, along with women who may be pregnant during the flu season, residents of nursing homes or chronic care facilities.

    If unprotected by an effective influenza vaccination given to such patient populations, influenza has a greater ability to penetrate hosts and create complications.

    These complications may include deadly diseases, such as bacterial pneumonia or encephalitis.

    Symptoms of influenza usually start to express themselves symptomatically about two days or so after being infected with the virus.

    Over 10 percent of the population is infected with this virus every year- resulting in about 200,000 hospitalizations and nearly 40,000 deaths, according to the Center For Disease Control (CDC).

    Those who do survive an influenza infection allow others to obtain antibodies from them to develop other antibodies for future viral outbreaks.

    The antibodies are used to produce vaccines to prevent acquisition of the damaging effects of influenza.

    Yet this is only if the antibodies contained in the influenza vaccine are effective against the suspected particular influenza strains that are present during the influenza season.

    Specifically, it is usually what is known as strept pneumo bacteria that kill those due to an infection of these microbes due to being invaded by influenza, ultimately.

    This is the type of bacteria that typically infect a person suffering from influenza who may have compromised immune systems, as mentioned earlier.

    In these cases, the bacteria are allowed to thrive at a higher and more deadly rate.

    On average, it takes over a week for one to die after being infected by influenza that has the power to cause death in particular human populations.

    Pandemic flu outbreaks, such as the one that happened that was mentioned earlier was an influenza strain so powerful that it overkills the cells of its host.

    The influenza virus has this ability on occasion, and its efficacy is dependent on its mutations that have developed over time that make it more powerful than other influenza viruses.

    The flu vaccination is trivalent- meaning it contains three viral strains of suspected viruses for flu outbreaks during a particular winter season.

    The viral strains are determined by the World Health Organization, as well as the Centers for Disease Control, and other organizations.

    Yet one should keep in mind that these three strains of influenza may not even exist in a particular flu season.

    The vaccination is a guess, at best, yet is certainly better than the absence of a flu vaccination.

    Unfortunately, the influenza vaccine administered last flu season was believed to be largely ineffective due to unsuspected strains of the virus infecting others.

    Although about 140 million injections of this vaccine were administered, this proved to be pointless for preventative medicine for influenza during this season.

    The most recent flu season was fairly mild, according to the CDC.

    After giving the vaccination dose to one, it takes about 10 days for that person to build up the immunity for the disease of influenza.

    The months of October to December are recommended to receive this vaccine.

    And the vaccine is about 50 percent effective in offering protection from influenza, according to others, if one calculates the previous flu seasons with flu vaccinations.

    Vaccines are a catalyst for antibody production in humans, which protect them against the virus, if the influenza virus happens to present itself within them.

    The influenza vaccines can be given by injection or nasally.

    The flu season that is now occurring was supplied with 150 million vaccines in the United States.

    However, some studies have shown that this vaccine is rather ineffective based on incidences of the acquisition of the influenza virus by others, initial reports have indicated.

    The influenza season peaks between the months of January and March.

    The vaccine for this influenza season is manufactured by 6 different companies in preparation for this timeframe of the influenza season.

    Also, it takes manufacturers about 6 months to make and formulate the influenza vaccination.

    The influenza vaccine is produced every year according to which type of virus types that may be prevalent during a particular flu season.

    The presence of influenza can be widespread in certain states, yet not others. The vaccination is recommended to be administered to those who are at high risk, such as the chronically ill.

    Also, it is recommended that those under 18 years of age get the vaccine, as well as those people over the age of 50.

    Pregnant women should receive the immunization. Health care personnel are always encouraged to get a flu vaccine as well.

    Such populations of those recommended to receive the flu vaccination are those believed to need the protection the vaccine may offer the most.

    This is of concern, as influenza can progress rapidly into the more serious illnesses mentioned earlier that can lead to death.

    Anti-virals, on the other hand, decrease greatly the ability for viruses to reproduce once established in a human.

    That seems like it should be a focus during viral seasons instead of any vaccination that exist today regarding the disease of influenza.

    Yet, as with antibiotics, viruses can become resistant to anti-virals as well.

    Yet the strains chosen for the influenza vaccine contain what are speculated influenza viruses.

    So the vaccine is ineffective if a new and dominant influenza viral strain that possibly could cause a pandemic happens to be present during an influenza season.

    With the influenza virus, again it can have the ability to kill mammals, as well as birds, along with humans at times.

    The concern that there is an influenza strain that exists that has the ability to mutate.

    If this happens, the viruses have the ability to share genetic data between separate life forms as they, multiply within each one of them with ease.

    This is the case with what is known as the Avian Flu, as well as the Swine Flu.

    The most recent avian influenza virus was identified in China in 1997. Called the H5N1 virus subtype, it has the potential to be the next flu pandemic.

    The last Swine Flu outbreak occured in the United States during the mid 1970s.

    However, the virus responsible for the pandemic mentioned earlier was an avian influenza, which was called the H1N1 influenza virus.

    This virus, unlike the human influenza virus, has a longer incubation period- about 5 days.

    Also, H5N1 has the ability to mutate more rapidly, as well as replicate at a similar speed.

    Avian influenza viruses are highly pathogenic. No one fully understands the influenza virus and its rapid ability to mutate.

    This is because this particularly malicious virus is the result of two separate influenza viruses acquiring the same host at the same time.

    As a result of mutual sharing of genetic material between the two viruses, novel attributes are allowed to develop and create a H5N1 that obviously prove to be rather deadly.

    The H5N1 Avian influenza virus seems to have become progressively more pathogenic in the past decade, according to others.

    The letters H and N, by the way, stand for the antigens HA and NA-and are the letters of proteins that protrude from the viral shell.

    It is these proteins that mutate so often with the influenza virus, and which is why we continue to be infected with this virus.

    With the Avian Influenza existing with the H5N1 strain, millions of birds have been slaughtered due to the danger and unpredictability of this strain.

    The first recorded incidence of human-to-human transmission of the H5N1 virus was believed to be in Thailand in 2004.

    There have been outbreaks of Avian flu in about 10 or 20 countries in the world so far- with Indonesia appearing to be the worst.

    Migratory birds spread this influenza virus between continents.

    The pathogenic strength of the H5N1strain varies due to constant re-assortment or switching of genetic material between the viruses.

    This essentially creates hybrid modifications of what it was before this occurs due to this re-assortment that makes this virus much more virulent.

    So far, nearly a half a million people worldwide have been infected with this strain.

    Also, about half have died from the infection caused by this H5N1 influenza virus.

    Vaccinations are being developed and reformulated constantly at this time due to the pandemic threat of the H5N1 Influenza virus, and most recently, the swine flu virus.

    http://www.cdc.org/flu/weekly

    Dan Abshear

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The Loom

A blog about life, past and future. Written by DISCOVER contributing editor and columnist Carl Zimmer.

About Carl Zimmer

Carl Zimmer writes about science regularly for The New York Times and magazines such as DISCOVER, which also hosts his blog, The LoomHe is the author of 12 books, the most recent of which is Science Ink: Tattoos of the Science Obsessed.

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