More than half of all healthcare workers in the developing world, including Africa, are unknowingly infected with deadly tuberculosis (TB), according to a report on the Science and Development Network’s website.
The study, published in the online journal Medicine by the open-source Public Library of Science, highlights the risk of TB transmission from patients to healthcare workers — and onward into the general community.
According to the authors, who include Rajnish Joshi of the Mahatma Gandhi Institute of Medical Sciences in Maharashtra state in India and Arthur Reingold of the University of California Berkeley in the United States, the TB infections also have a subsequent negative effect on health services.
However, this problem is frequently neglected in countries that lack the resources or community mobilisation to prevent it.
The researchers reviewed 51 published studies concerning healthcare workers and TB in several developing countries, including India, Malawi, Uganda, South Africa and Peru.
Their analysis shows that, on average, 54% of the healthcare workers have latent TB, in which the microscopic bacterium responsible for the disease causes no symptoms but remains in the body. About a third of the world’s population is latently infected with mycobacterium TB.
The scientists found that the level of active disease among healthcare workers is higher than among the general population. The longer that healthcare workers were exposed to TB, the higher was the prevalence of latent infection. Many cases could be directly attributed to occupational exposure.
Certain workplaces, such as in-patient TB facilities, laboratories and emergency facilities, carried a higher risk of infection. Some occupations, such as radiology technicians and nurses, were also more likely to be infected.
Drug resistance
More than 90% of the world’s TB cases are found in hospitals in developing countries, from the Russian Federation to Brazil. Many of these facilities lack the resources to prevent TB transmission. But simple measures, such as early diagnosis, segregation of infectious patients and better training of healthcare workers, can make a big improvement, the authors note.
They also say that further research into cheap and effective prevention measures in resource-limited settings is needed — particularly with the emergence of extensively drug-resistant TB in countries such as South Africa.
Multi-drug-resistant TB is more widespread than thought, warn researchers from the Global Project on Anti-Tuberculosis Drug Resistance Surveillance.
Misusing antimicrobial drugs can lead to multi-drug-resistant TB, which is defined as resistant to the two most powerful anti-tuberculosis drugs, Isoniazid and Rifampicin.
But researchers warn that multi-drug-resistant TB is only the precursor to extensively drug-resistant TB, which is potentially incurable with available drugs. It resists all standard TB drugs and at least one of three second-class drugs.
Looking at four of the six most widely used TB drugs, the scientists found that both multiple and extensive drug resistance were causing growing numbers of new infections, especially in parts of China and the former Soviet Union. The results have been published in the medical journal the Lancet.
Increase in cases
In the 79 countries surveyed between 1999 and 2002, multi-drug resistance in new TB cases ranged from zero to 14%. Resistance to just one drug ranged from zero to 57%. In Botswana, however, there has been a worrying increase in resistance to any available TB drugs. The researchers estimate that 424 000 cases of multi-drug-resistant TB emerged worldwide in 2004. Half of the new cases of multi-drug-resistant TB were in China, India and Russia alone.
Expensive drugs are needed to treat multi-drug-resistant TB. But because the multi-drug-treatment is lengthy and difficult, patients often fail to follow it through. This can lead to extensively resistant TB, which is resilient to first- and second-line drugs.
The emergence of extensively resistant strains is “extremely worrisome”, says the report. This type of TB is particularly worrying for people living with HIV/Aids or otherwise compromised immune systems. TB killed almost two million people in 2004, many of whom were co-infected with HIV.
“The findings of the global project emphasise the importance of implementing sound tuberculosis control activities to prevent further creation of multi-drug resistance,” said Mario Raviglione, of the World Health Organisation (WHO), which led the project with the International Union against Tuberculosis and Lung Disease.
The results also reveal the need to include high-quality treatment for multi-drug resistance in routine control programmes, said Raviglione, head of the WHO’s Stop TB department. He warned that extensively drug-resistant TB will be fatal, particularly in regions (such as South Africa) with considerable numbers of HIV infections.
The second Open Forum on TB Drug Development last month stressed that ensuring the effective use of drugs is as crucial to TB control as is developing new drugs.
“What we need first and foremost is innovation,” said Maria Freire, president of the Tuberculosis Alliance, which convened the forum in London, United Kingdom. — SciDev.Net
On the net
International Union against Tuberculosis and Lung Disease
Global Project on Drug Resistance Surveillance