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Pandemics through history
There have been a number of significant pandemics in human history, all of them generally zoonoses that came about with domestication of animals - such as influenza and tuberculosis. There have been a number of particularly significant epidemics that deserve mention above the 'mere' destruction of cities:
Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence. Disease killed the entire native (Guanches) population of the Canary Islands in the 16th century. Half the native population of Hispaniola in 1518 was killed by smallpox. Smallpox also ravaged Mexico in the 1520s, killing 150,000 in Tenochtitlán alone, including the emperor, and Peru in the 1530s, aiding the European conquerors. Measles killed a further two million Mexican natives in the 1600s. As late as 1848-49, as many as 40,000 out of 150,000 Hawaiians are estimated to have died of measles, whooping cough and influenza. About 12,000 years ago, a sudden wave of mammal extinctions swept through the Americas. Ross MacPhee of the American Museum of Natural History argues the culprit was extremely virulent disease, which humans helped transport as they migrated into the New World.
Plague
Antonine Plague, 165-180. Possibly smallpox brought back from the Near East; killed a quarter of those infected and up to five million in all. At the height of a second outbreak (251-266) 5,000 people a day were said to be dying in Rome.
Plague of Justinian, started 541. The first recorded outbreak of the bubonic plague. It started in Egypt and reached Constantinople the following spring, killing (according to the Byzantine chronicler Procopius) 10,000 a day at its height and perhaps 40 per cent of the city's inhabitants. It went on to destroy up to a quarter of the human population of the eastern Mediterranean.
The Black Death, started 1300s. Eight hundred years after the last outbreak, the bubonic plague returned to Europe. Starting in Asia, the disease reached Mediterranean and western Europe in 1348 (possibly from Italian merchants fleeing fighting in the Crimea), and killed twenty million Europeans in six years, a quarter of the total population and up to a half in the worst-affected urban areas.
Cholera
- Cholera first pandemic 1816-1826. Previously restricted to the Indian subcontinent, the pandemic began in Bengal, then spread across India by 1820. It extended as far as China and the Caspian Sea before receding.
- Cholera second pandemic (1829-1851) reached Europe, London in 1832, New York in the same year, and the Pacific coast of North America by 1834.
- The third Cholera pandemic (1852-1860) mainly affected Russia, with over a million deaths.
- The fourth pandemic (1863-1875) spread mostly in Europe and Africa.
- The sixth pandemic (1899-1923) had little effect in Europe because of advances in public health, but Russia was badly affected again.
- The seventh pandemic began in Indonesia in 1961, called El Tor after the strain, and reached Bangladesh in 1963, India in 1964, and the USSR in 1966.
Influenza
The "Spanish Flu", 1918-1919. Began in August 1918 in three disparate locations: Brest, Boston and Freetown. An unusually severe and deadly strain of influenza spread worldwide. The disease spread across the world, killing 25 million in the course of six months; some estimates put the total of those killed worldwide at over twice that number. An estimated 17 million died in India, 500,000 in the USA and 200,000 in the UK. It vanished within 18 months and the actual strain was never determined, though some recent attempts at reconstructing genes from the virus have been successful.
Typhus
The epidemic disease of wartime was typhus, sometimes called "camp fever" because of its pattern of flaring up in times of strife. (It is also known as "gaol fever" and "ship fever", for its habits of spreading wildly in cramped quarters, such as jails and ships.) Emerging during the Crusades, it had its first impact in Europe in 1489 in Spain. During fighting between the Christian Spaniards and the Muslims in Granada, the Spanish lost 3,000 to war casualties and 20,000 to typhus. In 1528 the French lost 18,000 troops in Italy and lost supremacy in Italy to the Spanish. In 1542, 30,000 people died of typhus while fighting the Ottomans in the Balkans. The disease also played a major role in the destruction of Napoleon's grande armée in Russia in 1811. Typhus also killed numerous prisoners in the Nazi concentration camps during World War II.
There are also a number of unknown diseases that were extremely serious but have now vanished, so the etiology of these diseases cannot be established. During the Peloponnesian War in 430 BCE, an unknown agent killed a quarter of the Athenian troops and a quarter of the population over four years. This disease fatally weakened the dominance of Athens, but the sheer virulence of the disease prevented its wider spread; i.e. it killed off its hosts at a rate faster than they could spread it.
Concern about possible future pandemics
A report says Aids, tuberculosis (TB), measles, malaria, diarrhoeal diseases such as dysentery and cholera, and acute respiratory infections such as pneumonia are responsible for 90% of all deaths due to infectious diseases. Nevertheless, there is little chance that in the current conditions, these diseases turn into pandemics. However, it is also possible that a mutation of the genes or the collapse of the Health prevention system in Western countries render the current protection ineffective.
Antibiotic-resistant superbugs may also revive diseases previously regarded as 'conquered' such as cholera and measles that have developed new resistance to antibiotics. Intensive agriculture and land development is bringing humans closer to animal pathogens. International travel means diseases can spread faster than ever.
"It is not in the interests of a virus to kill all of its hosts, so a virus is unlikely to wipe out the human race, but it could cause a serious setback for a number of years. We can never be completely prepared for what nature will do: nature is the ultimate bioterrorist."
Diseases that may possibly attain pandemic proportions include Lassa fever, Rift Valley fever, Marburg virus, Ebola virus and Bolivian haemorrhagic fever.
Influenza
There is a historical record of Influenza pandemics of varying severity at 20-40 year intervals. In February 2004, avian influenza virus was detected in pigs in Vietnam, increasing fears of the emergence of new variant strains. At the moment the most serious concern is H5 avian influenza in chickens in south-east Asia. If this virus learns to transmit from human to human then it could sweep rapidly around the world.
It is feared that if the avian influenza virus undergoes antigenic shift with a human influenza virus, the new subtype created could be both highly contagious and highly lethal in humans. The 1918 influenza outbreak caused 20m deaths in just one year: more than all the people killed in the first world war. A similar outbreak now could have a perhaps more devastating impact.
Malaria
Malaria is a public health problem in some 90 countries, and causes between 1.5 and 2.7 million deaths world-wide each year. It is caused by a parasite called a Plasmodium, which is passed on from infected humans when they are bitten by mosquitoes, which then go on to bite non-infected people.
The symptoms are bouts of fever, tiredness, headache, nausea, and muscular pain, leading, without treatment, to delirium, convulsions and death.
If treated promptly, it is a curable disease, and travellers are advised to take a course of anti-malaria drugs to protect them before going abroad.
However, nothing can provide 100% protection against malarial infection.
AIDS
AIDS, or Acquired Immune Deficiency Syndrome, is linked to HIV virus, which can be passed from human to human through blood to blood contact. AIDS can be considered a global pandemic but it is currently most extensive in southern and eastern Africa.
Although HIV is symptomless, over time, it reduces the body's ability to deal with outside infections.
When the body's immune system has been rendered ineffective, it is highly vulnerable to other predatory infections, such as TB, which may have already been lying dormant.
Although once full-blown AIDS has developed, it becomes increasingly difficult to treat these infections, the HIV-positive stage can be lengthened by many years using modern anti-viral treatments.
AIDS is commonly spread by unprotected sexual intercourse, both homosexual and heterosexual, and is a major killer in developing countries, where there is a higher degree of infection in the heterosexual community, and less use of protection such as condoms.
In these countries, immune resistance is generally lower due to poorer nutrition and general health, and consequently, the development of full-blown AIDS, and death from opportunistic infections is far swifter.
Tuberculosis
Tuberculosis is a lung disease caused by infection with a bacteria. In developing countries, where poorer nutrition and living conditions have reduced children's natural immune response to the virus infection, it is often fatal.
Its symptoms are a persistent cough, which may involve coughing up blood, fevers, night-sweats, weight loss and tiredness.
Once contracted, it can lie dormant in the lung, only developing into the disease if the body's immune system weakens.
Treatment is by a six-month course of antibiotics, and provided this is followed, the cure rate is high.
However, symptoms generally disappear long before the end of the treatment course, and the failure of many people to continue for the full six months has been blamed for the emergence of TB strains resistant to antibiotics.
Diarrhoeal Diseases
Clean water prevents outbreaks of diarrhoeic disease. Poor hygiene and water supplies are the main factors behind the spread of diseases like dysentery and cholera.
Both, although quite treatable, cause death through dehydration, as the body cannot replace the water and body salts it loses through diarrhoea attacks.
All are far more prevalent in developing countries, which may have no efficient sewage disposal system, leading to the contamination of water supplies.
More recently, the breakdown of proper water treatment facilities in eastern European countries such as Latvia has led to outbreaks of diseases like cholera.
Acute respiratory infections
Pneumonia is a term used to refer to a variety of lung infections caused by viruses, bacteria and parasites. In 2003, there were concerns that SARS, a new highly contagious form of pneumonia, might have become pandemic.
Common symptoms include fever, a cough, rapid breathing, chest pain, and perhaps a bluish or grey colour of the lips or fingertips, indicating that the body is not getting enough oxygen through the lungs.
One of the most dangerous forms is Pertussis, or Whooping Cough, which is prevented in many parts of the world by a vaccination.
Once an infection has taken hold, a principal treatment, either given to tackle the bacterial infection itself or act prophylactically.
Young children in developing countries, many immuno-suppressed and suffering from other infections, find it extremely difficult to fight off the disease.
Many respiratory tract infections are very infectious, particularly in the early stages, and can be spread through droplets from sneezes or coughs, or from dirty tissues or water glasses.
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