* Swine flu could threaten millions with HIV, tuberculosis
* Immune-weakened people may struggle to fight new virus
* WHO appeals for continued attention to other diseases
By Laura MacInnis
GENEVA, April 29 (Reuters) - The swine flu outbreak, which has killed up to 160 people, could be especially dangerous for millions of people already battling other infections, such as HIV or tuberculosis, health experts said.
A 23-month-old child died in Texas on Wednesday, becoming the first death from swine flu outside Mexico, where the H1N1 strain raised alarms when it killed young adults who are normally more resilient than babies and the elderly.
The virus has caused mainly minor symptoms in countries with confirmed infections outside Mexico, and the outbreak remains tiny in scale compared to other epidemics such as malaria, hepatitis, cholera and meningitis.
However, as it continues to spread epidemiologists worry that swine flu could have a devastating impact on people whose immune systems are weak due to the AIDS virus or other diseases.
World Health Organisation (WHO) spokesman Gregory Hartl said adults who suffered severe pneumonia and died from the virus in Mexico may in fact have fallen into this category.
"It is a question which a lot of our scientists have been looking at," Hartl told reporters in Geneva on Tuesday, when asked why the deaths so far have been clustered in Mexico.
"Maybe people were infected with other illnesses too that made their illness more severe. Maybe they were immunologically suppressed," he said.
LOW IMMUNITY LEVELS KEY
According to WHO estimates, there are 33 million people infected with immune-weakening HIV worldwide, and another 9 million people are diagnosed with tuberculosis every year, a disease that only rears its head when immunity levels are low.
If swine flu infiltrates those communities, and takes hold in impoverished and densely-populated areas such as urban slums, where tropical and other diseases are rife, health experts expect the outbreak could quickly become more severe.
With health budgets already stretched by the global economic downturn, WHO officials are appealing to governments to keep ensuring HIV and tuberculosis patients get the drugs they need to stay strong, and to improve access to medical care and testing facilities in poor areas.
"Many of the world's poorest people are particularly vulnerable to lethal airborne diseases," said Glenn Thomas, a spokesman for the Stop TB Partnership.
"With health resources already stretched in low income countries, a new disease pandemic could jeopardize effective TB control and other health programmes," he said.
WHO Acting Assistant Director-General Keiji Fukuda stressed that while it is important to keep a close watch on swine flu -- in case it ramps up into a full-blown pandemic -- other epidemics and diseases need continued attention and care.
But we are also mindful that even in this kind of situation other urgent health matters and issues do not go away," he said.