As the world's population continues to grow at an alarming rate, new microbes are developing to feed on an abundant food supply: humans. Each year new and deadly diseases hit the headlines: the filoviruses; E. coli 0157:H7; Legionnaire's disease; Lyme disease; and HIV and AIDS. Meanwhile, well known illnesses we thought we had conquered - such as influenza, tuberculosis, and bubonic plague - continue to evolve into new and more deadly strains as they become resistant to conventional antibiotics.

Filoviruses are possibly the most dangerous new forms of disease to have come to light in recent years, and can cause severe illness including haemorrhagic fevers and often death. One of these, the Marburg virus, was first identified in 1967, in an outbreak that killed seven people. It was found in a pharmaceutical factory in the German town of Marburg, which imported monkeys from east Africa for research.

Nine years later, in 1976, another filovirus, Ebola, hit Zaire (now the Democratic Republic of Congo) and 9 out of 10 of those infected there died. One of the survivors was a scientist at Porton Down, the UK government microbiological lab, who accidentally infected himself while investigating the virus. Subsequent fears that Britain would experience an epidemic of this terrifying disease were luckily unfounded.

Then in 1989 a related form of the same filovirus, called Reston, was carried by monkeys brought to the USA after a complicated journey that brought the animals into contact with other monkeys and people in four continents. This case brought into focus just how quickly hundreds of people around the globe can be exposed to a potentially deadly new virus before it has even been identified, or contained.

Fortunately predictions of a devastating filovirus epidemic were unfounded, and this strain of the virus was subsequently found to be harmless to humans, but the threat of a filovirus epidemic still strikes fear into the heart of the medical authorities.

Fifty years ago, when penicillin was fairly new, it could cure almost every case of infection caused by the common staphylococcus bacteria. Over time however, bacteria have absorbed part of penicillin's genetic material into their DNA, and as a result penicillin has been rendered ineffectual - curing only 10 per cent of cases today. This pattern has been repeated with each successive advance in antibiotics as the targeted bacteria evolves to outwit the treatment.

Today there is a whole new breed of bacteria that cause 'old' diseases (such as pneumonia, sexually transmitted diseases, dysentery and tuberculosis) that are now resistant to traditional antibiotics. The situation has been worsened by the over-prescription of antibiotics for all manner of ailments, by patients not finishing their antibiotics, and by the extensive use of antibiotics in animals intended for human consumption.

The bacterium Eschericia coli (E. coli) is one of the common bacteria that people carry in their intestines. However, a dangerous form of E. coli (0157:H7), that causes intestinal haemorrhaging, has emerged due to evolutionary processes and through the unregulated use of antibiotics for livestock.

There have been serious outbreaks in Britain, the USA and elsewhere: in 1997, a Scottish outbreak infected hundreds, especially the very young and the elderly, and killed at least twenty people. The source of infection was eventually traced to cooked meats supplied by a butcher. Basic food hygiene precautions are usually all that is required to prevent the spread of infection.

New diseases are not just a problem of the poor, some emerge specifically because of our wealthy western society. In1976 a strange new disease emerged affecting members of the American Legion who had attended a convention in a grand Philadelphia hotel. Exhaustive tests failed to find the cause, until finally a rare type of bacterium - legionella - was discovered.

Legionella lives in a film of scum on the surface of water, in dark, oxygen deficient places. In the case of the first outbreak, it was inhaled from air conditioning units. Although many air conditioning systems have been redesigned to prevent further infection, legionella still lurks. The disease has been identified in many places since, although usually as an isolated incident rather than mass infection, and it has even been found in showers. Of those who contract it one in every ten will die.

Humans again, unwittingly, created the environment for new disease by radically changing the wooded environment in inhabited parts of the world. As a result of clearing forests, particularly in New England in the USA, ticks that usually fed on mice and deer began to feed off humans and passed them a bacterium. The resulting Lyme disease (named after the Connecticut town where it was first identified) has since been found in many different parts of the world. It causes similar symptoms to rheumatoid arthritis and can cause long-term disability and even death.

No new disease has gripped the imagination and the world to a greater extent than AIDS and HIV (the human immuno-deficiency virus that is associated with it - (WRONGLY, see vaccines List ... Ed). Its origins are obscure. Scientists believe that it originated from an isolated and rare virus in Africa, which exploded on to the world scene in the 1980s. It is most commonly transmitted sexually, or through contaminated blood products. Its spread has also been encouraged by extensive international travel, war and particularly by sexual liberation and intravenous drug-abuse.

AIDS is the number one killer virus and has the potential to cripple the human race. Its effects are at their starkest in many of the poorest parts of Africa, where poverty means that drugs to control infection are not available and a lack of effective sex education hastens its spread. The UN conference on AIDS in Africa, held in July 2000, highlighted the bleak future for many African countries, with extremely low life expectancies, the varying degrees of success in dealing with the problem, and the potential loss of a whole generation. Few were hopeful, and some predicted chaos and war in the wake of AIDS.

Nature's ability to adapt is amazing - but the consequences of that adaptation are that mutations of old diseases, we thought were long gone, may come back to haunt us. But of all these new and old diseases, AIDS poses the greatest threat. It has the capacity to mutate and evolve into new forms, and the treatments that are being developed have to take account of that. Yet the recent history of life-threatening and lethal diseases suggests that even if we conquer this disease, and all the others described here, there may be yet another dangerous micro-organism waiting in the wings. The golden age of conquering disease may be drawing to an end. Modern life, particularly increased mobility, is facilitating the spread of viruses. In fact, some experts believe it will be a virus that leads to the eventual extinction of the human race.

Channel 5 Television, 22 Long Acre, London WC2E 9LY.

Published in 2000 by Channel 5 Broadcasting Ltd. Project co-ordinator: BBS, Author: David Souden. For further copies of this fact sheet please send a stamped, self addressed envelope to: Air Sick, PO Box 55, London W12 8UE; or ring the Channel 5 order line on 0990 555055 (calls cost a maximum of 8p per minute.) Alternatively visit the website at: www.channel5.co.uk

Useful Resources

The Royal Free Travel Health Centre: operates an advice service during normal office hours. Tel: -20 7830 2885. www.travel-health.co.uk

The United Nations AIDS programme: the largest coordinated international effort to combat the disease. www.unaids.org

The TB Network: deals with issues on the spread and resurgence of tuberculosis. www.tbnetwork.co.uk.
The National AIDS Help line: Tel- 0800 567123

The Terrence Higgins Trust Help line: deals with enquiries about HIV and AIDS (12 noon to10 pm daily). 52 Grays Inn Road, London WC1. Tel- 020 72421010. www.tht.org.uk.

The Centers for Disease Control and Prevention: Based in Atlanta, Georgia, USA. They are in the front line of investigation, and provide up-to-date information on emerging and virulent diseases. www.cdc.gov

The World Health Organisation: Is the United Nations agency for health and medicine. It provides background detail and information on outbreaks and incidence for a whole range of infectious diseases. www.who.int/health-topics.

AIDS 2000 conference: This was held in Durban, South Africa. Its website provides news and proceedings. www.aids2000.com.