The Greatest Benefit to Mankind. Roy Porter

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СКАЧАТЬ period of ten to seventeen days. The fever lasts from two to six hours, returning every third day (hence ‘tertian’); marked by vomiting and diarrhoea, such attacks may recur for two months or longer. In time, as Greek doctors observed, the spleen enlarges, and the patient becomes anaemic and sometimes jaundiced. Quartan malaria, caused by Plasmodium malariae, is another mild variety.

      Malignant tertian malaria, caused by Plasmodium falciparum, is the most lethal, producing at least 95 per cent of all malarial deaths. The incubation period is shorter but the fever more prolonged; it may be continuous, remittent or intermittent. Plasmodium falciparum proliferates fast, producing massive destruction of red blood cells and hence dangerous anaemia; the liver and spleen also become enlarged.

      Malaria may sometimes appear as quotidian fever, with attacks lasting six to twelve hours – the result of multiple infection. Patients may also develop malarial cachexia, with yellowing of the skin and severe spleen and liver enlargement; autopsy shows both organs darkened with a black pigment derived from the haemoglobin of the destroyed red blood cells. What the ancients called melancholy may have been a malarial condition.

      Malaria shadowed agricultural settlements. From Africa, it became established in the Near and Middle East and the Mediterranean littoral. The huge attention Graeco-Roman medicine paid to ‘remittent fevers’ shows how seriously the region was affected, and some historians maintain the disease played its part in the decline and fall of the Roman empire. Within living memory, malaria remained serious in the Roman Campagna and the Pontine marshes along Italy’s west coast.

      Coastal Africa was and remains heavily malarial, as are the Congo, the Niger and hundreds of other river basins. Indigenous West African populations developed a genetically controlled characteristic, the ‘sickle-cell’, which conferred immunity against virulent Plasmodium falciparum. But, though protective, this starves its bearers, who are prone to debility and premature death: typical of such evolutionary trade-offs, gains and losses are finely balanced.

      India was also ripe for malarial infection. Ayurvedic medical texts (see Chapter Six) confirm the antiquity of the disease in the subcontinent. China, too, became heavily infected, especially the coastal strip from Shanghai to Macao. And from the sixteenth century Europeans shipped it to Mesoamerica: vivax malaria went to the New World in the blood of the Spanish conquistadores, while falciparum malaria arrived with the African slaves whom the Europeans imported to replace the natives they and their pestilences had wiped out.

      Malaria was just one health threat among many which set in with civilization as vermin learned to cohabit with humans, insects spread gastroenteric disorders, and contact with rodents led to human rickettsial (lice-, mite- and tick-borne) arbo diseases like typhus. Despite such infections encouraged by dense settlement and its waste and dirt, man’s restless inventive energies ensured that communities, no matter how unhealthy, bred rising populations; and more humans spawned more diseases in upward spirals, temporarily and locally checked but never terminated. Around 10,000 BC, before agriculture, the globe’s human population may have been around 5 million; by 500 BC it had probably leapt to 100 million; by the second century AD that may have doubled; the 1990 figure was some 5,292 million, with projections suggesting 12 billion by 2100.

      Growing numbers led to meagre diets, the weak and poor inevitably bearing the brunt. But though humans were often malnourished, parasite-riddled and pestilence-smitten, they were not totally defenceless. Survivors of epidemics acquired some protection, and the mechanisms of evolution meant that these acquired sophisticated immune systems enabling them to coexist in a ceaseless war with their microbial assailants. Immunities passed from mothers across the placenta or through breast-feeding gave infants some defence against germ invasion. Tolerance was likewise developed towards parasitic worms, and certain groups developed genetic shields, as with the sickle-cell trait. Biological adaptation might thus take the edge off lethal afflictions.

      THE ERA OF EPIDEMICS

      Some diseases, however, were not so readily coped with: those caused by the zoonoses (animal diseases transmissible to man) which menaced once civilization developed. By 3000 BC cities like Babylon, with populations of scores of thousands, were rising in Mesopotamia and Egypt, in the Indus Valley and on the Yellow River, and later in Mesoamerica. In the Old World, such settlements often maintained huge cattle herds, from which lethal pathogens, including smallpox, spread to humans, while originally zoonostic conditions – diphtheria, influenza, chickenpox, mumps – and other illnesses also had a devastating impact. Unlike malaria, these needed no carriers; being directly contagious, they spread readily and rapidly.

      The era of epidemics began. And though some immunity would develop amongst the afflicted populations, the incessant outreach of civilization meant that merchants, mariners and marauders would inevitably bridge pathogen pools, spilling diseases onto virgin susceptibles. One nation’s familiar ‘tamed’ disease would be another’s plague, as trade, travel and war detonated pathological explosions.

      The immediate consequence of the invasion of a town by smallpox or another infection was a fulminating epidemic and subsequent decimation. Population recovery would then get under way, only for survivors’ heirs to be blitzed by the same or a different pestilence, and yet another, in tide upon tide. Settlements big enough to host such contagions might shrink to become too tiny. With almost everybody slain or immune, the pestilences would withdraw, victims of their own success, moving on to storm other virgin populations, like raiders seeking fresh spoils. New diseases thus operated as brutal Malthusian checks, sometimes shaping the destinies of nations.

      Cities assumed a decisive epidemiological role, being magnets for pathogens no less than people. Until the nineteenth century, towns were so insanitary that their populations never replaced themselves by reproduction, multiplying only thanks to the influx of rural surpluses who were tragically infection-prone. In this challenge and response process, sturdy urban survivors turned into an immunological elite – a virulently infectious swarm perilous to less seasoned incomers, confirming the notoriety of towns as death-traps.

      The Old Testament records the epidemics the Lord hurled upon the Egypt of the pharaohs, and from Greek times historians noted their melancholy toll. The Peloponnesian War of 431 to 404 BC, the ‘world war’ between Athens and Sparta, spotlights the traffic in pestilence that came with civilization. Before that war the Greeks had suffered from malaria and probably tuberculosis, diphtheria and influenza, but they had been spared truly calamitous plagues. Reputedly beginning in Africa and spreading to Persia, an unknown epidemic hit Greece in 430 BC, and its impact on Athens was portrayed by Thucydides (460 – after 404 BC). Victims were poleaxed by headaches, coughing, vomiting, chest pains and convulsions. Their bodies became reddish or livid, with blisters and ulcers; the malady often descended into the bowels before death spared sufferers further misery. The Greek historian thought it killed a quarter of the Athenian troops, persisting on the mainland for a further four years and annihilating a similar proportion of the population.

      What was it? Smallpox, plague, measles, typhus, ergotism and even syphilis have been proposed in a parlour game played by epidemiologists. Whatever it was, by killing or immunizing them, it destroyed the Greeks’ ability to host it and, proving too virulent for its own good, the disease disappeared. With it passed the great age of Athens. Most early nations probably experienced such disasters, but Greece alone had a Thucydides to record it.

      Epidemics worsened with the rise of Rome. With victories in Macedonia and Greece (146 BC), Persia (64 BC) and finally Egypt (30 BC), the Roman legions vanquished much of the known world, but deadly pathogens were thus given free passage around the empire, spreading to the Eternal City itself. The first serious outbreak, the so-called Antonine plague (probably smallpox which had smouldered in Africa or Asia before being brought back from the Near East by Roman troops) slew a quarter of the inhabitants in stricken areas between AD 165 and 180, some five million people in all. A second, between AD 211 and 266, reportedly СКАЧАТЬ