Re-Emerging Microbes
The reappearance of microbes that had been successfully conquered or controlled by medicines and vaccines is distressing to the scientific and medical communities, as well as to the public. One major cause of disease re-emergence is that microbes responsible for causing these diseases are becoming resistant to the drugs used to treat them. Also, the decrease in vaccine use for vaccine-preventable diseases is contributing to re-emergence of previously controlled diseases. Some examples of re-emerging infectious diseases that are of significant public health concern are TB, malaria, and polio.
TB (Tuberculosis)
According to the World Health Organization (WHO), nearly 2 billion people, one-third of the world’s population, are infected with Mycobacterium tuberculosis, the bacterium that causes TB. This includes between 10 and 15 million people in the United States.
TB is the world’s leading cause of death from a single infectious organism, killing 2 million people each year. Failure to stop the spread of TB can be attributed to several factors, including
- The co-epidemic with HIV/AIDS which has led to more
and more TB cases developing in people with weakened
immune systems
- The failure of infected people to complete the entire drug treatment needed to eliminate the disease (this treatment may take up to 9 months to complete)
- The emergence of MDR TB (multidrug-resistant TB) and XDR TB (extremely drug resistant TB), which do not respond to available treatments
WHO estimates that 500,000 people worldwide have MDR TB, while the frequently fatal XDR TB has been detected in 46 countries.
As a result of these many factors, a disease that was once considered “old” and curable is making a strong comeback in resource-poor countries and is also re-emerging in the United States.
Malaria
Malaria, the most deadly of all tropical parasitic diseases, has been resurging dramatically in recent years. Increasing resistance of Plasmodium protozoa (one of the microbes that causes malaria) to inexpensive and effective medicines presents problems for treating active infections. WHO estimates between 300 million and 500 million new cases of malaria occur worldwide each year, causing more than 1 million deaths annually. In the United States, approximately 1,300 cases are reported annually. Most of the U.S. cases occur in people who had been infected while traveling abroad. Other cases occur in people bitten by infected mosquitoes in the United States.
Polio
Polio is another disease that had come close to eradication (elimination), due to the widespread use of polio vaccines. Recently, however, polio has been re-emerging. According to the Global Polio Eradication Initiative, global polio eradication efforts have resulted in a reduction from 350,000 cases in 1988 to fewer than 2,000 cases worldwide in 2006. Only four countries continue to see new polio cases (Nigeria, India, Pakistan, and Afghanistan,). There are ongoing efforts to increase vaccine coverage in these areas.
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