In 1918, a flu pandemic swept the world. No one really knows how many people died of flu in 1918, but scientists estimate that it was somewhere between twenty and one-hundred million people. The numbers feel sterile, so here's a more poetic view.
Grandmother Speaks of the Old Country
Lola Haskins
That year there were many deaths in the village.
Germs flew like angels from one house to the next
and every family gave up its own. Mothers
died at their mending. Children fell at school.
Of three hundred twenty, there were eleven left.
Then, quietly, the sun set on a day when no one
died. And the angels whispered among themselves.
And that evening, as he sat on the stone steps,
your grandfather felt a small wind on his neck
when all the trees were still. And he would tell us
always, how he had felt that night, on the skin
of his own neck, the angels, passing.
from Desire Lines: New and Selected Poems, BOA Editions, 2004
I've enjoyed some of the flu diaries. As a student of flu for the past 12 years, I offer some of my own perspective on the history, epidemiology after the fold.
When I was a young boy, there was an epidemic of German measles (rubella). I had been vaccinated, but my brother got it. I absorbed my mother's sense of dread. When mothers got together (and I listened), they would recite lists of children who had been sick or hospitalized.
Most of us have never experienced a genuine epidemic, a plague. The memories have been lost. During the 80s, some people felt the dread as HIV/AIDS was spreading. Nowadays, HIV/AIDS is highly prevalent in some areas of the USA, especially around Washington, DC, but the epidemic is moving slowly. HIV/AIDS is far worse in Africa today, more like a plague in some places, where there's a funeral to mourn the passing of a friend every week.
In the USA, infectious diseases have been declining as a cause of death. TB and malaria kill more than a million people each year (~1.4 and ~1.2 million, respectively), but most of those deaths happen somewhere else. TB in the USA has been declining for more than a century, and all the malaria is imported.
Childhood epidemics of measles and rubella are a thing of the past, thanks to excellent vaccination programs.
My "Uncle Bill," my grandpa's brother, used to hobble around on a walker. His legs were shriveled and useless from polio. Now, polio is so rare in the USA, it makes the news if someone gets it. Polio is on the brink of eradication, but the endgame won't be easy.
Smallpox was eradicated -- and it cost a lot of money to get rid of it. Smallpox used to kill a million people or more each year, but no one even needs a vaccine today. The result? The smallpox eradication campaign pays for itself about every 28 days.
Most of the infectious diseases that used to circulate are being prevented by vaccines. Kids still get runny noses and earaches, and you can still get a sexually transmitted diseases or a hospital-acquired infection, but you're more likely to die of a heart attack or stroke.
You only get measles once, or you an prevent it with a vaccine. Flu is different because you can get flu many times.
To be more specific, when people say "flu" they mean lots of things. To most people, flu is anything that gives you a fever and makes you ache. Flu is short for Influenza (or influence), and it refers specifically to viruses that are all "related." The one that matters most to this discussion is called Influenza A
Influenza A "strains" are distinct lineages of the virus that have been circulating in the population. They are given names like this: "H1N1" or "H3N2" or "H5N1." The H stands for hemagluttanin the N stands for neuraminidase, two proteins that are the targets of the human immune response. The number stands for different gene families. There are many different kinds of H and N that exist, mostly circulating in wild bird populations, but only a few human types are in regular circulation.
When someone gets infected with some particular flu virus, say H1N1, they form an immune response. If the exact same virus came around next year, they would be immune. The virus evolves -- point mutations that arise from simple DNA base-pair replication errors change the shape of the H protein. These occur often enough that, after a few years, the virus escapes the shadow of the immune response that the last flu virus generated. The process of steady change through the accumulation of lots of these mutations is called "drift." Already, this makes flu different from measles because you can get flu several times.
Influenza A is, however, different in another way. Viruses are fairly simple structures -- either DNA or RNA wrapped in protein. Many viruses have all those instructions on a single strand of DNA or RNA. Influenza A is an RNA virus. The RNA comes in five pieces. If two different Influenza A viruses infect the same cell, then the virus that comes out can mix and match the pieces of the two parent strains. This is the viral equivalent of sex. Very rarely, this can happen to create a new kind of human influenza A virus. What comes out is often defective. Very rarely, a new flu virus comes out that can spread. This is called "shift."
When a shift happens, the new virus can spread very quickly because on one is immune.
The 1918 flu was an H1N1 virus that was, presumably, created by one of these rare "shift" events. The result killed about 25 people out of every thousand people infected. The odds of surviving the 1918 flu were pretty good, butthe virus spread so well and infected so many people that the number of deaths added up. After a few years, the 1918 flu had mutated. The case fatality rate had fallen, and the H1N1 started the process of mutation and immune evasion.
In 1957, there was another shift that brought H2N2 that killed around a million people, and H1N1 disappeared. In 1968, another shift happened and killed a million people. H2N2 disappeared. Sometime during the 1970s, H1N1 reappeared, and it looked a lot like the strain that disappeared in 1957.
Recently, "bird flu" has been in the news. It's an influenza A virus called H5N1 that can be highly pathogenic in birds and that can infect humans. It has rarely spread from one human to another, however, so the impact on humans has been limited.
There have been other flu scares. The most relevant was a previous outbreak of "swine flu" in 1976, starting with a soldier at Ft. Dix. That epidemic disappeared on its own.
Emerging infectious diseases have been in the news, including SARS, west nile virus, Bird flu. These epidemics are often treated as being equally scary. This has led some people to speculate that The risks were exaggerated. That's not how I see it -- there were important differences.
SARS was the real deal -- it spread from human to human, and it looked like it had the potential to cause a pandemic. While they were very serious issues, bird flu and west nile virus never posed the same level of threat. Bird flu, as I've already said, rarely spread from one human to another. West nile virus infects many species of birds and it is spread by many species of mosquitoes, but the human cases trickled in. Neither bird flu nor west nile virus had the potential to grow like a snowball rolling down hill. SARS had that potential, even though transmission was relatively slow. When SARS was eradicated, it prevented a great calamity.
This epidemic is another H1N1 flu strain, like the 1918 flu. It's called "swine flu" because the "shift" happened in a pig. We'll be learning about it over the coming weeks, but here are a few basics.
- My personal rule of thumb has been that if there were more than a thousand cases, a new flu strain was probably not going to be contained. I think we've gone too far, and I don't think we're going to contain it. This flu has already spread to several countries, just counting the cases that we know about.
- Flu season occurs in the late fall and early winter months. Flu transmission is slower here now, but it may not be slow enough. Even if transmission is slow here, the flu season will be starting in the southern hemisphere. Even if we get rid of all the swine flu in the USA today, it will be hard to contain it everywhere. It might be back in the fall.
- If we do get a full-blown epidemic, most people will probably survive it. Even in 1918, during the height of the pandemic, there was scarcely a mention of it in the papers, aside from the obituaries. It wasn't a plague like the old country. Another way to look at the 1918 flu is that 97.5% of the humans who got it survived. The most important measure of the total number of global deaths will be the case-fatality rate. Will the epidemic elsewhere look more like the Mexico cases or more like the USA cases?
- The virus will probably change over the next few months. It might get more deadly, or it might get less deadly.
- Flu might kill you by itself, but another way to die is from bacterial pneumonia that follows. If you're really worried about this, now's a good time to stop smoking.
- There's still a chance that we'll contain this epidemic, and it's worth spending a lot of money to contain it.
- Everyone can do their part in small ways. Some of these fall under the category of "protect yourself" and other fall under the category of "protect others." Why not do both? Think consciously about how you might be spreading the flu or putting yourself at risk. Do the little things. Don't go to work if you think you might have the flu, and if you're an employer, give your employees the benefit of the doubt to avoid having a whole bunch of sick people. If someone is sick at work, send them home and tell them to stay there until they're healthy. Then wash your hands. Wash your hands frequently and thoroughly. Avoid touching your eyes or your nose or your mouth with unwashed hands. Carry a handkerchief and use it to cover your mouth when you sneeze and cough, or do it into your sleeve. Wash your hands again. Some people claim that a saline rinse can help to prevent infection -- it probably won't hurt, but don't share your saline with anyone else. Drink lots of water. Get plenty of sleep. Eat healthy foods. Brush your teeth. Exercise (away from crowds.) Drive safely. Flu isn't the only way to go.
A personal note to end. The poem I opened with brings me close to tears. We are most human when we care for our sick and mourn our dead. We are at our best when we defeat our old enemies of plague, war, and starvation. The old enemies are still our most important ones. I will watch the news over the next few weeks on tenterhooks, but while the flu pandemic evolves, thousands will die of malaria, HIV/AIDS, TB and other diseases. Remember them and support public health here, and US efforts to improve public health abroad.