The Battle with Infectious Diseases

 

Infectious microbes – tiny organisms that include bacteria and viruses – are living entities with a nearly unlimited ability to adapt. Microbes reproduce approximately every 30 minutes. This event allows constant mutation, migration, and adaptation of these organisms, which are the basic building blocks for some of the world’s most virulent diseases. The new forms that survive their predators, which include antibiotics and antivirals, go on to reproduce, multiply, and thrive. Staying one step ahead of these survivors requires surveillance, testing, and the redesigning of strategies through research, development, and distribution of new medicines and vaccines.1,2

We develop antimicrobials in order to control symptoms, to destroy organisms, and to seek to eradicate diseases. With the development of new classes of antimicrobials in the 1950s and 60s, the scientific community prematurely thought it could claim victory over microbes. In fact, in the late 1960s, Surgeon General William H. Stewart stated it was “time to close the book on infectious diseases, declare the war against pestilence won, and shift national resources to such chronic problems as cancer and heart disease”.1,2

Yet some 40 years later, we continue to struggle with highly recognizable foes like malaria, tuberculosis and HIV, and newcomers like SARS. Five distinct threats have emerged in our evolving battle with infectious diseases: First, the resurgence of endemic diseases, especially in the developing world. Second, a growing link between microbes and chronic diseases. Third, drug-resistant microbes. Fourth, new emerging infections, and fifth, the threat of bioterrorism.

With so many sources for trouble, it’s little wonder that infectious diseases remain a dominant cause of death worldwide. In 2002, infectious diseases caused 26 percent of global deaths. Four million deaths were attributed to respiratory infections; 2.8 million to HIV/AIDS; 1.8 million to diarrhea; 1.6 million to TB; and 1.3 million to malaria.2

Several factors have coalesced to make this an ideal time for an emergence of infectious diseases, according to the Institute of Medicine. The microbes themselves have demonstrated truly remarkable genetic and biologic flexibility. We’re seeing changes in our physical environment, with global warming and weather patterns being favorable to microbes. Social, political, and economic factors, compounded by war and famine, have led to a breakdown in public health measures. Human behavior and activities bring people into contact with species of animals that harbor transmittable diseases. And finally, high speed travel and the threat of terrorism have the world on edge.3

Infectious diseases are a critical concern for developing nations, but they are no less active in more developed countries, especially as they associate with an explosion of chronic diseases. In fact, the role of infectious diseases in the creation of chronic diseases is becoming increasingly well defined. More than a half million new cases of stomach cancer each year are due to infection with Helicobacter pylori. Cervical cancer has been known for some time to be associated with infection from the human papilloma virus. About eight in 10 cases of liver cancer are the result of infection with hepatitis B or C. The Epstein-Barr virus is a group 1 carcinogen known to cause Hodgkin’s disease. And evidence is steadily mounting that Chlamydia pneumoniae may contribute to the progression of atherosclerosis.4,5,6

Clearly, greater investment in predictive science and preventive measures will be required if further pandemics are to be avoided. The Spanish Flu Pandemic in 1918 and 1919 killed nearly 50 million people worldwide. The 1957 to 1958 Asian Flu Pandemic and the 1968 to 1969 Hong Kong Flu claimed 1 million and 700,000, respectively. The progressive reduction in the number of deaths was primarily the result of effective antibiotics that controlled secondary bacterial infections.7

Today, some believe another massive flu pandemic is conceivable because of the converging elements of a “perfect storm.” These elements include, first, the possible emergence of a strain of influenza that is non-responsive to existing vaccines. Second, the association of the virus with a highly resistant secondary bacterial infection. And third, extraordinarily fast proliferation under the radar screen due to the hyper-mobility of today’s traveler’s. Consider that in 1950 we had 200 million travelers worldwide. Fifty years later, this number has increased seven fold to 1.4 billion and continues to grow.7 Charles Darwin said, “It is not the strongest of the species that survives, nor the most intelligent, but the one most responsive to change.” To manage microbes we need to change faster than they do.

For Health Politics, I’m Mike Magee.

References

1.World Health Organization. WHO Report on Global Surveillance of Epidemic-prone Infectious Disease. Geneva: WHO, 2003.

2.Emerging Crisis in Infectious Diseases: Challenges for the 21st Century. The Pfizer Journal. 2004;5:2.

3.Institutes of Medicine. Microbial Threats to Health: Emergence, Detection, and Response. Washington, D.C.: The National Academies Press, 2003.

4.American Society for Microbiology. New and Reemerging Infectious Diseases: A Global Crisis and Immediate Threat to the Nation’s Health, The Role of Research. Washington, D.C.: ASM, 1997. Cited in Emerging Crisis in Infectious Diseases.

5.Volume 70: Epstein-Barr virus and Kaposi’s sarcoma herpesvirus/human herpesvirus 8. IARC monographs on the Evaluation of Carcinogenic Risks to Humans. 1997. Cited in Emerging Crisis in Infectious Diseases.

6.Bahrmand AR, Bahadori M, et al. Chlamydia pneumonia DNA is more frequent in advanced than in mild atherosclerosis lesions. Scand J Infect Dis. 2004;36:119-123. Cited in Emerging Crisis in Infectious Diseases.

7.Kindhauser MK. Communicable diseases 2002; Global Defence Against the Infectious Disease Threat. Geneva: WHO, 2003. Cited in Emerging Crisis in Infectious Diseases.