By Sarah Long
19 March 2008 [MEDIAGLOBAL]: Tuberculosis (TB), a disease responsible for the deaths of an estimated 1.5 million people each year, continues to be a threat to the developed and developing world alike, reports the World Health Organization (WHO).
A report released Monday by the WHO, titled Global Tuberculosis Control 2008, concludes that global efforts to combat the disease have slowed in recent years, causing the WHO to call for renewed commitment to fighting tuberculosis around the world.
The emergence of new, drug resistant strains of tuberculosis is of particular concern. Cases that do not respond over six months to any of the medicines typically administered, collectively called “first line” drugs, are considered Multi-Drug Resistant (MDR). Of the 9.2 million new cases of TB in 2006, the WHO estimates that 500,000 were MDR-TB.
Treatment of MDR-TB requires so-called “second line drugs”, which can take years to effectively treat TB and are 100 times more expensive than first line treatments.
While some countries, such as Hong Kong, have shown significant decreases in incidence of MDR-TB, and the MDR-TB rates in several other nations are holding steady, Multi-Drug Resistant Tuberculosis is on the rise globally. Countries such as Peru, the Republic of Korea and the Russian Federation have seen what the WHO calls “concerning increases.”
Because MDR-TB can be passed between individuals as easily as drug-sensitive TB, the emergence of MDR-TB anywhere is cause for concern everywhere.
“TB and drug resistant TB affect the public, and this disease does not honor any borders,” Dr. Abigail Wright, WHO TB specialist and primary author of last month’s WHO report on MDR-TB, told MediaGlobal. “Governments and health systems of all countries must take drug resistance seriously”
MDR-TB on the Rise
“There are a variety of reasons for an increase in resistance, but most are program-related,” Wright said, explaining that unnecessary hospitalization can lead to infection. “Increases in resistance are due to weakness in health systems,” she said.
According to Dr. Edward Nardell, a physician and TB expert with Partners in Health, a Boston-based NGO that specializes in addressing and treating MDR-TB around the world, overcoming these weaknesses is a complex, multi-faceted process.
“The barriers are financial but [there are] also implementation bottlenecks even if the money were to appear,” Nardell told MediaGlobal. “Many programs wait for treatment failure, and many still follow the discredited old WHO policy of using Regimen 2, which is adding just one drug (streptomycin) to the failed standard regimen. This leads to more drug resistance and allows transmission to other patients of MDR-TB because the patient is still not effectively treated.”
In the absence of labs where strains can be analyzed for drug resistance, MDR-TB is often simply not identified at all, Nardell said.
“Only 30,000 MDR cases have been treated so far, and there are hundreds of thousands of cases each year,” he said. “In the 10 year WHO Global Plan to Stop TB (which is being revised) it was estimated that 800,000 cases will need to be treated, mostly in Eastern Europe, because there are laboratories there able to diagnose them. There are many more cases elsewhere that will go undiagnosed for lack of laboratories, and these will not be treated.”
One such area of high concern is sub-Saharan Africa, home to many of the world’s least developed countries. Because many African nations lack the technologies needed to identify resistance, very little is actually known about the extent of TB or MDR-TB on the continent.
What is known, however, is that in many African countries, incidence of MDR-TB is likely to be high both because of poor health care infrastructure, and because of the presence of another serious public health threat-HIV/AIDS.
While many people are infected with the bacterium that causes TB, it very often remains inactive and asymptomatic in the body. However, because AIDS weakens the immune system, people with AIDS are far more likely to become sick with TB if infected.
Of the 9.2 million new TB cases in 2006, the WHO reports that 700,000 were among people living with HIV. The WHO further estimates that TB is responsible for up to a third of all AIDS deaths, making it the leading cause of death among HIV-infected people. In 2006 alone, 200,000 people died from HIV-associated TB.
Because people with weakened immune systems are more vulnerable to tuberculosis, they are more likely to pass the disease on to others. “Lack of testing and treatment of HIV fuels the [TB] epidemic,” Nardell said.
The Trouble with Treatment: Second Line Drugs
Where MDR-TB is identified, the only course of treatment is to administer second line drugs, which are substantially more expensive than first line treatments, and have to be taken for a much longer time.
This increased cost can make treatment prohibitively expensive for impoverished nations facing outbreaks of MDR-TB. In response, the WHO has set up a Green Light Committee to help coordinate bulk purchases, making drugs more affordable.
Increased access to second line drugs, however, is in itself a cause for some concern. There is a significant risk that increasingly powerful medicines may set off a kind of epidemiological arms race. The more widely distributed these drugs become, the more chance there is that strains will develop that are resistant to the more advanced drugs as well.
“We know the second line drugs are bought, sold and used in many countries,” Wright told MediaGlobal. The Green Light Committee therefore also acts to “aid countries in setting up MDR-TB treatment programs to ensure that drugs are used properly, and so that we do not rapidly lose our last line of defense,” Wright said.
Already cases of extensively drug resistant TB (XDR-TB) have been reported, and there has been at least one confirmed case of tuberculosis that was resistant to all existing treatments.
Were TB to become completely drug resistant, even developed countries would be essentially powerless to fight the disease.
An increased incidence of completely resistant TB “is a very important possibility,” Wright said, adding that immediate action is needed to keep MDR-TB in check and ensure that programs are being both effective and careful in their treatment of MDR-TB with second line drugs.
What’s Next? The Need for Global Action
Despite the significant difficulties in fighting TB and MDR-TB, Nardell emphasized that it can be done if developed nations step up to the challenge.
“Controlling TB globally is the right thing to do from a humanitarian perspective,” Nardell told MediaGlobal. “The problem is there, but the resources are here, in the developed world, and we can, and have, shown that partnerships with poor countries can help them build their own effective programs.”
Investing in the control of TB in the developing world is also in the best interests of developed nations, Nardell said.
“In the US, more than 50 percent of TB cases are foreign-born, and if MDR-TB rises in those countries, arrivals will increasingly be infected by MDR-TB, potentially developing active, communicable disease here. They will be effectively treated here, but some transmission will occur before they are diagnosed. Moreover, global travel has never been easier. Visitors of all kinds, from business people to students, are increasingly going to parts of the world where MDR-TB is common.”
“The only sensible solution is for developed countries to use their resources to eradicate this problem from the world,” he said.
“Tackling this problem will take the global political will and resources that controlled smallpox and almost eradicated polio. Much progress has been made, but the next global report in two years is likely to be far worse, unless resources and implementation strategies are brought in at an unprecedented level,” he stressed. “This is a complex biosocial problem for which there are no easy answers. But there are answers.”