Fighting infectious diseases

Biotechnology is used extensively in the study of emerging infectious diseases. These are diseases that are:

  • new and previously unrecognised, such as SARS - Severe Acute Respiratory Syndrome, or
  • known diseases that have increased in number and spread over the past two decades, such as foot-and-mouth disease, or
  • diseases that threaten to increase in occurrence and severity in the near future, such as influenza.

Infectious diseases pose a threat to humans as they can pass quickly from person to person and affect a large number of people in a very short time.

A disease-causing agent is called a pathogen and can be a virus, bacterium or a prion. Their ability to infect and cause disease is referred to as pathogenicity.

There are a number of issues involved in emerging infectious diseases. Some of them are:

  • Growing tourism and trade, or political instability which results in more people and animals moving from one place to another. It can lead to a drop in standards of health or increase in the spread of infectious diseases, increasing the risk of transmitting disease from one place to another.
  • The evolution of new and more deadly disease-causing strains of infectious agents. Viruses and bacteria can naturally modify their genetic material over time (mutate). Some of these changes can increase their pathogenicity, while others can allow normally harmless pathogens to transmit disease.
  • Changes in climate and ecology can contribute to increases in vector-borne diseases (diseases carried by insects). The pathogens, their vectors (the insects that transmit them) and their hosts (the animals, including humans, that can be infected by them) can all be influenced by the environment.
    A change of just a few degrees Celsius could impact on the distribution of either a pathogen, its vector or its host. For example, mosquitoes, which carry a lot of diseases, prefer a warm climate. Global warming could increase the range of places where mosquitoes can live, allowing malaria to spread. Alternatively, people are increasingly encroaching into wilderness areas to farm, as vacant land becomes scarce. This increases those people’s exposure to wild animals, many of which may harbour bacteria or viruses that do not cause disease in the animal because they have evolved together, but may cause diseases in people who have never had contact with these bacteria or viruses before.

Human behaviour also allows pathogens to exploit new niches, such as hepatitis C, HIV, SARS and variant CJD (the human form of mad cow disease).

Biotechnology is used to study the genetic material of viruses, bacteria and other organisms like prions, and can work out whether a disease is caused by a totally new pathogen, or a new type (strain) of a known pathogen.

This information can be used to develop rapid diagnostic tests which enable specific detection and identification of a disease. This is important, as speedy detection of a pathogen can allow for a quick response to eradicate the disease, or develop vaccines and effective drugs for treating infections.