Epidemics

"A flea, a virus, a bacterium has changed human history more than the greatest emperors, the greatest armies, the most brilliant ideas. Epidemics have influenced human life to a greater extent than kings, wars and all heroes have ever done."

Of the 100 different diseases (most of them with many synonyms) documented in my database only about 1/5 occur frequently, in the table on this page 11 are named. Most of these common diseases are epidemic and some of them have caused world-wide pandemics. It is difficult for most people in high-income countries to realize the profound impact these epidemics had on populations and societies in the past. Today the figures for the total number of people killed in the past are confusing if not compared to population densities of today. In old times the emperor or king had absolute power and often took every single decision himself. When he was unexpectedly killed by an epidemic disease society became chaotic. Things stopped working. The sanitary conditions are not worth mentioning. Nobody had any idea how an epidemic disease spread. When a Duke or Count was infected and passed away, often everybody else in his castle became infected and died too. Poor people having nothing but immunity against the disease moved into the empty castle. The banquet in Luis Buñuel's movie Viridiana is a brilliant enactment of such situations. In Medieval times the noblemen and top clergy were the only people having any education and a little knowledge about other things than planting, harvesting, timber cutting, fishing, and their own country. There were no doctors, no vaccine, no medicines against anything.

Several diseases follow other natural distasters. Following earthquakes in southwestern USA a disease often called "valley fever", Coccidioidomycosis, with flu-like symtoms, occurs in some areas. It is caused by spores of microscopic fungi. Earthquakes trigger landslides during which soil masses are moving rapidly and soil particles are thrown up in the air as dust. Mixed with the soil particles are the spores of the fungus Coccidioides which cause the infection. In Indonesia, a severe earthquake in 1835 triggered the spread of a gall bladder disease.

Explosive volcanic eruptions pose so many health risks far away from the volcano that the International Volcanic Health Hazard Network (IVHHN) has published a special folder about them and how to avoid inhaling volcanic ash. Depending on the chemical composition of the magma, its ash looks very different under a microscope. Some ash is spiny or needle-like and inhaling such ash is as dangerous as inhaling asbestos. Some volcanoes are degassing toxic substances like hydrogen fluoride, HF, adhering to the ash particles. The ash is carried downwind and when it is raining the HF is taken up by the raindrops which end up on the ground. In Iceland sheep are killed by the thousands when grazing on grass that has been sprinkled with such HF. Even sublethal doses of HF cause small spines to form in certain parts of the skeleton. In Icelandic there is a special word for such spines, gaddur. Archaeologists outside Iceland have not fully realized the potential of the gaddur to date skeletons to the year of eruption and simultaneously getting the wind direction from Iceland at the time of eruption.

Epidemic diseases are spread with the speed of human travel. Smallpox has a long history, not the least through the Roman warfare in western Asia. Smallpox was first described in China in the 5th century and then spread from there in waves over Asia to Europe, but the oceans delayed its arrival to the New world. It was common in Europe in the first decades of the 16th century. It arrived to the West Indies already in 1507 and the epidemic became very severe. When the Spanish colonizers arrived in Haiti in 1518 they brought smallpox with them which caused an epidemic that killed a major part of the local population. The following year Hernán Cortés landed on the coast of Mexico and in 1520 a smallpox epidemic — probably via an infected Spanish slave from Cuba - killed almost 50% of the Aztec population including the emperor Cuitláhuac. In the South American continent smallpox had spread to Peru 1519. By 1520 about 8 million South Americans had been killed in smallpox epidemics. The European colonizers and traders brought a lot of other diseases with them, too many to be mentioned here.

In 1545 the worst series of epidemics in the Americas ever hit Mexico. The diseases causing this had a local catchall name, Cocoliztli. It killed 3 million people in Mexico 1545-1570 and another 2 million 1576-1577. This disease was a kind of hemorrhagic fever and at least some strains had mice as vectors. Virulent epidemics of it begin after a long period of drought. The following is a possible scenario. When heavy rains suddenly end a period of drought, the mice escape being flooded by moving to populated areas where shelter and food are easily accessible. A bacterial or virus disease can be transferred to humans by fleas, ticks, and others, or by contact with mice droppings or urine. Infected people die after 3-5 days. Cocoliztli had a story similar to that of the beginning of the bubonic/pneumonic plague in East Asia.

My database can be used to study positive and negative correlations between the scores of recurrent epidemics of many diseases and other natural disasters, for instance, drought, rain, hail, snowfall, unseasonal frost together with data about poor crops/harvests, hunger/famines, migrations, and population data during more than 80 generations.

EPIDEMICS-DISEASES subregister (pages)	3086
Diseases	1016
of which >15 pages
Bubonic + pneumonic plague	343
Smallpox	108
Influenza	90
Cholera	61
Typhus	44
Ergotism	36
Malaria	35
Leprosy/Hansen's disease	30
Dysentery	30
Measles	23
Blood diarrhea, Cocoliztli	16
Pandemics	40
Epidemics	2031
Africa	76
of which the major are
Egypt	22
Africa North	12
Africa East	12
Africa South	10
America Central	11
America North	49
America South	16
Arctic	1
Asia	482
of which >12
China	61
Indonesia	53
India	41
Thailand	39
Japan	30
Vietnam	14
Sri Lanka	14
Philippines	13
Australia-New Zealand	12
Europe	1336
of which the major are
Sweden	140
Europe	160
Italy	155
Byzantine Empire-Turkey	146
UK	79
Spain	72
France	70
Germany	60
Denmark	47
Russia	42
Norway	38
Mediterranean	44
Pacific Ocean	4