Top 10 Deadliest Diseases

One of the most tragic parts of being human is being afflicted by diseases with high morbidity and mortality. Here is our list of top 10 deadliest diseases ever known to man.
1.    AIDS; 25 million from 1981 to present
AIDS is a mix of infections and complications as a result of progressive damage to the body’s immune system caused by HIV. AIDS is now considered a pandemic.

2.    Influenza; 36,000 deaths annually
Influenza, which is more commonly known as flu, is a highly infectious disease that is caused by influenza virus. Transmission of the disease is by airborne and through physical contact.

3.    Spanish Flu, 1918-19; 100 million deaths
The flu pandemic that happened in 1918 is termed as a category 5 flu pandemic which was caused by the flu virus strain A with subtype H1N1.


4.    Bubonic Plague; 250 million deaths
This disease outbreak was mainly caused by fleas and rodents infected with Xenopsylla cheopsis. Humans were infected after being bitten by an affected rodent.

5.    Malaria; 2.7 million deaths annually
Malaria is an infectious disease which is vector-borne. The causative agent is the protozoan parasites. It is a common disease in the sub-tropics and tropical regions.


6.    Ebola; 160,000 deaths from 2000 to present
The Ebola virus was first isolated in1976 from the dual outbreaks that occurred in Zaire and Sudan. It is a zoonotic disease as it affects lowland apes as well as humans.

7.    Cholera; 12,000 deaths from 1991 to present
The epidemic or Asiatic cholera is a very serious type of diarrheal ailment caused by Vibrio cholera. The mode of transmission is by ingesting contaminated food and water.

8.    Smallpox; Population drop from 12 million to 235,000
Smallpox is a highly contagious viral disease that has two variants. The V major has a 35% mortality rate while the less severe V minor has a 1% mortality rate.

9.    Polio, 10,000 deaths from 1916 to present
Polio or infantile paralysis is a viral disease that is transmitted through the fecal-oral course.


10. Black Death; 75 million deaths
The Black Plague is the one of the most serious pandemic outbreak in modern history. It was believed to have started in Central Asia and affected Europe during the 13th century.

Ecology of Infectious Disease

Human diseases
Many disease organisms that threaten humans worldwide have complex life histories that are affected by both human and non-human attributes of the ecosystems in which they occur. For example,

• Lyme disease is carried by ticks that move about on mammal hosts such as deer and mice - environmental parameters that affect these non-human hosts have implications for human exposure to Lyme disease
• Rabies is a disease that is contracted by wildlife and can be passed on to humans. NCEAS researchers have assembled and analyzed an extensive database documenting rabid raccoons, refining predictions of rabies dynamics
• The bacterium causing the gastrointestinal disease cholera is waterborne and associated with microscopic crustaceans - climatic and environmental factors that affect hydrodynamics and the ecology of aquatic food webs can influence the dynamics of cholera
• The brain parasite that causes toxoplasmosis is passed among rats, cats, and humans; in humans, infection is associated with lifelong personality changes that may influence human culture
• NCEAS ecologists have formulated and applied cutting edge approaches in analysis and synthesis of human disease scenarios in recent years, improving our understanding of human disease risk

Disease and ecosystems
Ecologists have a growing awareness of the importance of pathogens and parasites in the evolution and ecology of natural systems.  Researchers at NCEAS have examined the evolutionary relationships between disease organisms and their hosts, as well as more modern alterations of pathogen and parasite dynamics by humans . For example:

• Introduced species have escaped many of the parasites of their native ranges ;
• The removal of predators that normally select sick individuals from prey groups may increase pathogen transmission among their populations, when diseased individuals continue living within groups ;
• Primate researchers have examined the role of social and feeding behavior in moderating infection by sexually transmitted diseases and parasites in non-human primates ;
• Disease is considered to be among the most significant causes of the modern coral reef decline, and warmer temperatures encourage some of the most common diseases on coral reefs ;
• Environmental warming and human activities, such as fishing, may have complex disease effects as warm temperatures seem to favor some pathogens and parasites, while decreasing the prevalence or severity of others , and human activities alter host abundance, behavior and environment

West Nile disease

What is it West Nile disease?

West Nile virus is spread through the bite of an infected mosquito. The mosquito can become infected after biting an infected bird and this can then be transmitted from the bird to humans.

There is no evidence to suggest that West Nile virus can be spread from person to person or animal to person.

Where am I at risk?

The West Nile virus was first discovered in the West Nile area of Uganda in 1937.

It is prevalent in North America, where two thirds of the East coast states have had cases. There has even been a case in California.

There have also been cases in Israel, Africa and Asia and parts of Eastern Europe.

There was a UK case of a bird with the antibodies of the West Nile virus, but there have been no human cases.

What are the symptoms?

The patient can incubate the disease for up to a fortnight after being bitten.

Many of the people who become infected will have either no symptoms or mild flu-like symptoms, which last a couple of days.

These can range from fever, headache and body aches to skin rashes on the trunk of the body and swollen lymph glands.

But more serious cases, less than 1% of those who become infected, can result in severe illness such as West Nile encephalitis or meningitis and sometimes lead to death.

Out of about 1,000 people who became infected in Europe recently there were about 40 deaths.

How do I protect myself?

Scientists have developed a vaccine for the disease and it was due to start human trials in late 2002.

But as yet there is no vaccine for travellers to use so the best way to protect yourself is to avoid being bitten by a mosquito.

The mosquitoes which carry this disease bite at dawn, dusk and early evening, so if you are travelling to an area where the disease is prevalent you should either stay indoors, or wear long sleeved shirts and long-trousers and wear insect repellent.

People travelling with young children should ensure that they use a specially prepared insect repellent, rather than the adult version.

Health in Somalia

The average Somali is struggling hard to receive a human treatment in the African Horn. Life in this part of the world has not been easy over the last decade. War, internal rebellion and economic breakdowns have left many thousands displaced. Children and women have come to bear the maximum brunt of these unsolicited evils. Malnutrition, disablement and fatal diseases are all too, very common. With the current war scene showing no signs of ending early, there are serious doubts raised over the sustenance of human life here.

[Undernourished children everywhere in Somalia]

Meanwhile, the UNICEF (United Nations Children’s Fund) has announced plans to immunize about 100,000 internally displaced people, comprising women and children.

Malaria

Blood engorged mosquito

Health challenges are becoming more numerous as new infectious diseases such as SARS, West Nile virus, and avian flu emerge. In addition, the accumulation of chemical pollutants in the environment is starting to take a toll. While infectious diseases are fairly well understood, the health effects of many environmental pollutants are not yet known.

Malaria has an economic impact.
Among the leading infectious diseases, malaria claims more than 1 million lives each year, 89 percent of them in Africa. The number of people who suffer from it most of their lives is many times greater. Economists estimates that reduced worker productivity and other costs associated with malaria are cutting economic growth by a full percentage point in heavily affected countries.

Although diseases such as malaria and cholera exact a heavy toll, there is no recent precedent of a disease affecting as many people as the HIV epidemic does. If not checked soon, HIV could take more lives during this century than were claimed by all the wars of the last century.

Since the human immunodeficiency virus was identified in 1981, it has spread worldwide, leading to the deaths of more than 25 million people. Today 22 million HIV-positive people live in sub-Saharan Africa, but only 2 million or so are being treated with anti-retroviral drugs. Infection rates are climbing. Countries like Botswana and Zimbabwe could lose more than a fifth of their adult populations within a decade.

Affecting every facet of life and every sector of the economy, the HIV epidemic in Africa is now a development problem--threatening not only to undermine future progress but also to eliminate past gains. It threatens food security by reducing the number of available field workers, undermines the educational system as it decimates the ranks of teachers and leaves millions of orphans in its wake, strains health care systems to the point where many are now unable to provide even basic care, and dries up foreign investment.

Exposure to industrial toxins and waste are on the increase.
While the HIV epidemic is concentrated in Africa, air and water pollutants are damaging the health of people everywhere. A joint study by the University of California and the Boston Medical Center shows that some 200 human diseases, ranging from cerebral palsy to testicular atrophy, are linked to pollutants.

Nowhere is pollution damaging human health more than in China, where deaths from cancer have now eclipsed those from heart ailments and cerebrovascular disease. A Ministry of Health survey of 30 cities and 78 counties that was released in 2007 reveals a rising tide of cancer. The new reality is that each year China grows richer and sicker.

The United States is also feeling the effects of pollution. In July 2005 the Environmental Working Group, in collaboration with Commonweal, released an analysis of umbilical cord blood from 10 randomly selected newborns in U.S. hospitals. They found a total of 287 chemicals in these tests.

The WHO reports an estimated 3 million deaths worldwide each year from air pollutants-three times the number of traffic fatalities. In the United States, air pollution each year claims 70,000 lives, compared with the country's 45,000 traffic deaths.

A U.K. research team reports a surprising rise in Alzheimer's and Parkinson's diseases, and in motor neuron disease generally, in 10 industrial countries-6 in Europe plus the United States, Japan, Canada, and Australia. Over an 18-year period, death rates from these diseases, mainly Alzheimer's, more than tripled for men and nearly doubled for women. This increase in dementia is likely linked to a rise in the concentration of pesticides, industrial effluents, car exhaust, and other pollutants in the environment.

Scientists are becoming increasingly concerned about the various effects of mercury, a potent neurotoxin, which now permeates the environment in virtually all countries with coal-burning power plants. EPA research indicates that one out of every six women of child-bearing age in the United States has enough mercury in her blood to harm a developing fetus.

No one knows exactly how many chemicals are manufactured today, but with the advent of synthetic chemicals the number of chemicals in use has climbed to over 100,000. A random blood test of Americans will show measurable amounts of easily 200 chemicals that did not exist a century ago. Most of these new chemicals have not been tested for toxicity.