John M. Barry wrote a terrific book a few years ago titled The Great Influenza. It is about the international flu of 1918, mis-named the Spanish flu, which killed millions of people.
(From the cover): "In the winter of 1918, the coldest the American midwest had ever endured, history's most lethal influenza virus was born. Over the next year it flourished, killing as many as 100 million people. It killed more people in twenty-four weeks than AIDs has killed in twenty-four years, more people in a year than the Black Death of the Middle Ages killed in a century."
One of the interesting things about the 1918 flu was that the death rate was highest among young, healthy people. In normal flu, it is the infants and the old people who are at highest risk of death. But in the 1918 flu, it was the young, the strong, who died. When the flu germ enters people's bodies, the body's immune system fights back by sending out white blood cells to attack the flu germs and kill them. That combination -- the extra white blood cells and the dead germs -- creates a waste material inside the body -- mucus, for a cold, for example -- which must be expelled for the body to heal.
These young, healthy people's immune systems put up such a valiant struggle that their bodies actually became impacted with the waste products, and that is what killed them. The proper, highly-effective functioning of their immune systems killed them.
This 1918 flu began during World War I. It started I think in the spring, with a mild version causing little note, then came back months later in its deadly form. Young men from all over the United States were being drafted and sent to Europe to fight in World War I. They were brought to certain military make-shift bases for training, then transferred to the East Coast of the country, then shipped to various places in Europe. In the military bases, the only shelter they could put together on such short notice for so many young men draftees were tents.
So in the middle of winter in Iowa, in the freezing cold, knee-deep snow, thousands of young American men lived and slept inside poorly-insulated tents, sleeping on cots, often with inadequate blankets, all breathing the same air. When the flu first surfaced it was in these military camps, but nobody understand it was more than just a bad cold, so the draftees were not quarentined. Some would be exposed, get up the next day and ship out to the East Coast, be put on a ship, maybe die on the way, some carried it with them to Europe, including to Spain, so Spain got the blame for the 1918 pandemic.
It is of course impossible for an electric fence or the National Guard to prevent disease from crossing our border. Maybe the western world will finally wake up and realize that we need to have a wealth tax, take the 50% of the world's assets away from the 2% who own them, sell the assets and use the money to eliminate poverty, create communities for all people in which they have food, shelter, education, healthcare, sanitation, and functioning government systems that will be alert to outbreaks and have the resources to immediately contain them.
Or, in the alternative, we can continue to allow much of the world to live in dire, severe, deadly poverty, and wait until most of them die -- or maybe most of the world dies. If not this flu, then the next one. If not the flu, then some other disease. It's inevitable that millions, maybe hundreds of millions will die from disease unless we end the terrible inequality that condemns so many to an early and needless death. And oh yes: since we don't even have a national healthcare system in our own country, our own people will in many cases never go to the doctor or report a problem unless they are near death, because they can't afford to. So just like in Mexico, the failure in our country to have a single-payor government-provided system free of charge to the citizens could contribute to the deadly spread of a disease such as influenza.