The world's largest disease outbreaks and threats

(Reuters) -The new swine flu virus that has killed up to 159 people in Mexico and one Mexican baby in the United States remains tiny in scale compared to other global epidemics.

Following are details of the some of the world's largest disease outbreaks and threats:

* HIV/AIDS:

-- An estimated 33 million people worldwide are living with HIV, an immunity-destroying disease that spreads mainly through sexual contact, blood transfusions and needle-sharing. Almost all live in developing countries.

-- Every year about 2.5 million people are newly-infected with the virus and 2 million die from AIDS-related causes. Drugs known as antiretrovirals, taken on a continual basis, have been shown to extend the lifespan of people with the disease.

-- HIV/AIDS has killed more than 25 million people worldwide. It is the leading cause of death in sub-Saharan Africa and the fourth-leading cause of death globally.

* TUBERCULOSIS:

-- One third of the world's population -- more than 2 billion people -- are infected with the bacterium causing tuberculosis, a disease affecting mainly the lungs.

-- About 9 million people develop the disease each year when their immune systems weaken, normally from illness or pregnancy. In 2007 there were 1.3 million tuberculosis deaths among people without HIV, and 456,000 deaths among people infected with both tuberculosis and HIV.

-- Tuberculosis can normally be treated with antibiotics, but drug-resistant forms of the disease have made it increasingly hard, and costly, to treat.

* MALARIA

-- Almost half the world's population, 3.3 billion people, are at risk from malaria, a tropical disease that is transmitted from human to human by mosquitoes.

-- Each year nearly 1 million people die from malaria, mostly children under the age of 5, and 189 million to 327 million are diagnosed with the disease that can be prevented with drugs.

-- Those at highest risk include children, pregnant women, travelers, refugees, and migrant workers in endemic areas.

* INFLUENZA:

-- Between 3 million and 5 million people experience severe illness due to regular, seasonal flu around the world each year, and between 250,000 and 500,000 die as a result.