Infectious diseases are among the leading causes of death in the world. There are diseases that have emerged periodically in recent years. Some are being recognized for the first time as newly-emerging diseases. Others are re-emerging diseases that have been recognized in the past but have become greater threat than before. Communicable diseases are continuously evolving. Over time, there are emerging and re-emerging infections that pose a continued threat to humankind.
Some of these diseases, like Acquired Immune Deficiency Syndrome (AIDS), have become so deadly that they have been classified as a global threat. Another example would be the 2003 outbreakof Severe Acute Respiratory Syndrome (SARS) caused by a new form of the corona virus. Scientists are still working to discover a cure or effective treatment of many of these newly emerging diseases.
New diseases which have not been previously observed in humans are categorized as newly emerging infections. Various factors contribute to their emergence, such as environmental changes, increased urbanization, emigration, and population growth resulting in increased pollution and poor sanitation.
Some examples of newly emerging diseases include the Human Immunodeficiency Virus or HIV (first isolated in 1983), the Ebola virus (first reported in 1977), Hepatitis C (identified in 1989), the Escherichia coli bacterium (detected in 1982), and the influenza A (H5N1) virus (first recorded in humans in 1997).
There are diseases which have been recognized in the past but have become much more prevalent in recent years, either occurring more frequently, occurring in locations where they did not occur previously, or being diagnosed in a greater range of patient types. Re-emergence of diseases is caused by some of the same factors as those that propagate newly emerging diseases. These include microbial evolution, infections passing from animals to humans, and environmental changes. Climate can also be a factor in the re-emergence or resurgence of some diseases, such as cholera and malaria which have been associated with the El Nino phenomenon. Increasing numbers of people with immune deficiency and immunosuppression (associated with disease like AIDS as well as with medical treatments such as transplantation and chemotherapy for cancer) has paved the way for the re-emergence of many opportunistic infections. Some examples of re-emerging diseases are the following:
- Malaria. In the past decades, the insecticide dichlorodiphenyltrichchloroethane (DDT) was widely used to control malaria-carrying mosquitoes which spread malaria. But DDT fell into disuse due to concerns about its harmful effects on humans and wildlife, and the malaria parasite has developed resistance to anti-malaria drugs such as chloroquine and mefloquine. Current efforts against the disease include the development of new drugs and vaccines, as well as re-establishing public health measures such as sanitation and the use of mosquito nets.
- Tuberculosis. For well over a century, tuberculosis has been a disease associated with the poor who are made more vulnerable by congested and unsanitary living conditions. Thus, the population increase in poor communities has made the disease difficult to control. Incorrect or insufficient administration of antibiotics has led to drug-resistant strains of the disease. the spread of AIDS has also helped contribute to the re-emergence of tuberculosis, since immune deficiency greatly increases the risk of latent tuberculosis infections becoming active and being transmitted to others.
There are also infections described as “deliberately emerging”, caused by microbes that are intentionally used to cause harm to others, for warfare, terrorism, or other purposes. these include naturally occurring microorganisms such as anthrax, as well as those that have been genetically engineered or enhanced to be more dangerous.
Surveillance and quick-response- involving rapid diagnosis, detection, and containment – are the key strategies when responding to epidemics and other public health risks caused by emerging and re-emerging diseases. The World Health Organization demonstrated these when it coordinated the global efforts to curb the 2003 SARS outbreak. For as long as infectious diseases continue to emerge and re-emerge all over the world, these strategies will be essential.
There are no boundaries when it comes to infectious diseases. Apart from the threats posed by emerging and re-emerging diseases, everyone must be cognizant of our responsibility to chemical, biological, radiological, and nuclear attacks as well. Add to these the increasing resistance of serious infectious diseases like tuberculosis and malaria, to available treatments.
Foreign government agencies such as the US Food and Drug Administration are in the forefront of identifying and developing vaccines to protect against new diseases.