Tuberculosis, a contagious airborne disease that is increasingly resistant to drugs, infects about a third of the world's population and kills nearly two million people a year.

In some areas, one in four people with tuberculosis has a form of the disease that no longer responds to standard drugs, according to a new report by the World Health Organization. WHO estimated that 440,000 people had multidrug-resistant TB in 2008 and a third of them died.

With global travel and migration, "TB anywhere is TB everywhere," said Peter Small, the senior program officer for TB at the Bill & Melinda Gates Foundation, who manages an annual grant budget of $120 million. He said the disease is at a critical tipping point, where new tools to diagnose and fight it are being developed, but co-infection with HIV is fueling an epidemic and drug resistant TB poses an unprecedented global threat. Below is an edited Q&A.

Q: In what parts of the world is TB most concentrated?

The highest rates of TB are in sub-Saharan Africa, where there's a convergence of TB and HIV. The highest number of cases are in China and India. That's where the largest number of drug resistant cases are.

In China and India, it's largely because of the size and density of the countries. It's also a consequence of the loosely controlled use of antibiotics. You can literally buy them over the counter.

A couple of years ago there was a great deal of attention over an attorney with drug resistant TB who flew across the ocean. That story sort of put a human face to the fact that with modern population movement and migration, TB may be [more prevalent] in some areas, but that doesn't mean it's not an issue for everyone.

Q: What work is being done in Seattle?

Seattle is a critical node in the global fight against the antiquated technologies we're using -- a 125-year old diagnostic test and an 80-year old vaccine. There are now rapid DNA-based tests that can tell you within hours, not weeks, with certainty that a person has TB. The test I am thinking of is about $25, but there is a whole pipeline of tests coming in the next five years or so that are cheaper and easier to use. For Seattle we are making huge progress in making better tools to fight TB. (Organizations involved include Seattle Biomedical Research Institute, Infectious Disease Research Institute, the University of Washington and the Institute for Systems Biology).

We've made tremendous progress using a simple approach. Now we have these critical new challenges but innovation coming on line that can put TB control into the next gear. There are six TB vaccines now in human trials, we have nine drug molecules which are in human trials and already available to be mixed and matched to get best the treatments and at least a dozen diagnostic tests.

Q: Have you had TB yourself?

When TB is in a family, only about a third of the people get infected, and why is it that? Do they have different immune systems or did they inhale at the wrong time? I absolutely have no idea, and to be perfectly honest I'm not even convinced that I'm not infected with TB. The test is imperfect and I've spent a significant amount of time in the presence of infectious TB cases. It speaks to the thin veneer of understanding upon which our response to TB is based.

The focus is on identifying and treating those who have symptoms -- those who are infectious to others.

Q: Can you explain the differences in the types of TB that are emerging and treatments?

Standard TB is cured 95 percent of the time with $20 worth of antibiotics. Multidrug-resistant TB (MDR-TB) is a bacteria resistant to those antibiotics, Treatment still can likely be achieved with a 75 percent cure rate. But now it takes 18 months of antibiotics, some of which are quite toxic, maybe on par with cancer treatment, and the cost is $5,000. But there are some cases, extensively drug-resistant TB (XDR-TB), which are resistant to all known antibiotics.

Q: Can someone catch TB on an airplane?

It's possible and statistically pretty unlikely, but the fact that it is possible and has happened is a reminder that public health is really about ensuring the health of the general public. It's not just about taking care of poor people; it's not a generosity issue.

If anyone has TB, that is a public health threat for everybody around them. So ensuring everyone in the U.S. who has TB is diagnosed and treated is a central public health challenge.
_____________________________________________________________________

On Wednesday evening, four health experts and a TB survivor will hold a public forum at the Olympic Sculpture Park Pavilion to discuss the worldwide epidemic as part of World TB Day. Details are here. In 2009 there were about 250 cases of TB reported in Washington state, more than half in King County.