Sidenote: Hope you're finding this useful? I have always been curious about this matter. And when I found very little quality information about it, I decided to share a part of what I've learned about it - which is why this article came to be written. Read on.
Diseases have the potential to turn into epidemics, however none have been as devastating in history as the Black Death (Bubonic Plague) which rampaged the earth for the better part of 2 centuries having a death toll in the millions. A new disease The Bird Flu (H5N1) has recently cropped up (2003) and there are some similarities between this disease and the Black Plague which are too scary to ignore.
The Black Death broke out in China in the early 1300s and quickly spread Westward into Europe and throughout the world. The Avian (bird) Flu also had its initial breakout in the East (Vietnam) in 2003 and has been steadily moving west to include countries such as China, Thailand, Indonesia, Egypt and Turkey to name a few.
Animal hosts which spread the virus were key in both diseases. For the Bubonic Plague it was rats which carried fleas which were capable of infecting humans. These rats stowed away on boats which aided in the transmission of the disease across the continents. In the Bird Flu it is the birds which carry the disease. With the ability of flight and the fact that this disease can strike domestic species as well as wild birds which often migrate, the potential for the disease to spread rapidly is very real.
In fact in order for a disease to be considered a pandemic (rampant or uncontrollable disease), three conditions must be met.
1. A new form of a virus subtype must emerge for which there is little or no human immunity.
2. The virus must be able to infect humans and cause illness.
3. It must spread easily and without interruption among humans.
The Avian Flu has met the first 2 conditions listed above with nearly 300 cases of human infection causing illnesses such as fever, cough, sore throat, muscles ache, eye infections, pneumonia and even severe respiratory distress. There is little human resistance to this disease as infected individuals show a mortality rate of greater then 50%.
Fortunately the third criterion has yet to be met. To date, the only method of transmission is from direct contact with excretions or secretions or surfaces covered in these materials from infected birds. Human to human infection has in a few rare cases occurred but has not gone beyond a single individual. This means that while the disease is dangerous it is difficult for humans to become infected at this stage.
Another danger lies in the possibility of the virus being able to infect other intermediary hosts. To date the virus has been found in birds, pigs, cats (both large and domestic) and ferrets. In laboratory testing dogs have been able to be artificially infected with the virus but it has not been shown to occur in the natural world. Domestic and feral cats have become infected by eating raw meat of infected birds, however to date cats have not been able to pass the disease on to humans.
Viruses mutate at a vast rate (often within a few months), however many mutations are possible. Some make the virus more virulent (dangerous) while others can make it benign (safe). However it is a guessing game as to which form the new mutations will take on.
The Black Death was so devastating partially because modern medicine did not exist and vaccinations, antibiotics and antiviral medications were not available. Today the Bird flu has been shown to be resistant to 2 of the 4 antiviral medications on the market today (the other 2 have yet to be tested). No vaccine has been developed for this strain of Flu virus so currently the effects of the Bird Flu could be similar to those of the Black Death if it were to become rampant in the human population.
Although the similarities are scary currently there is no need for excessive alarm regarding the Bird Flu as human infection rate is low. Vigilance from the various World Health Organizations is needed to keep track of the Avian Flus progress and also to aid in the development of vaccinations and treatments for this virus in the case that a mutation occurs which allows it to pass freely through the human population.
Evangeline Siri is an amercian biologist that studied in Missouri, Florida and now continues disease research near Bangkok Thailand. Her website is http://www.AvianBirdFluDefense.com