Global Health Tom D. Y. Chin, MD, MPH

This lecture was given to the first year medical students at the University of Kansas School of Medicine in 2005

West Nile Virus  First isolated from the blood of a patient in Uganda in  The virus spread to Egypt, Middle East, Northern Mediterranean, Western Asia.  It was introduced in New York City in 1999, probably from Israel.  Since then, it has spread extensively throughout the United States.  It is spread by primarily mosquito bites

Life cycle of WNV

This knowledge has a direct impact on the practice of medicine and public health

Infectious Diseases Worldwide Size of the Problem  Biggest killers of children and young adults: >13 million deaths per year.  Particularly important in developing countries: average of 1 in 2 die of infectious disease.  In developing countries, the leading cause of deaths.  Developed countries, 3rd leading cause of deaths.

HIV/AIDS MALARIA TUBERCULOSIS ACUTE RESPIRATORY INFECTIONS DIARRHEAL DISEASES MEASLES

Disability-adjusted life years or years of health life lost

AIDS Pandemic  AIDS undoubtedly was one of the most devastating diseases emerged during the 20 th century.  From 1981 to the end of 2004, 24.9 million people world-wide have succumbed to HIV infections.  The pandemic is expected to progress well into the 21th century.

HIV/AIDS  AIDS is caused by a virus--human immunodeficiency virus.  Virus destroys the immune system. Thus termed acquired immunodeficiency syndrome or AIDS  AIDS represents complications of HIV infection when the immune system is sufficiently lowered.

Prevalence of HIV Infections End of 2004  Estimated 39.4 million people world-wide are living with HIV/AIDS.  2/3 of infected persons reside in Africa where the epidemic originated.  1/5 of those with HIV/AIDS are among people in Southeast Asia where the epidemic has been progressing rapidly. This area with the population of >2 billion may well be the future epicenter.

Global HIV/AIDS Epidemic  During the year million people became infected with HIV (incidence) 3.1 million people died of AIDS

HIV/AIDS in U.S.  At the end of 2003, a total of 902, 223 cases of AIDS have been reported to the CDC, 505,801 (56%) have died.  About 1 million of U.S. residents are living with HIV/AIDS

Primary Modes of Transmission  Globally, unprotected sexual intercourse between men and women is the predominant mode of transmission. Ratio M:F 1:1.1  In Sub-Saharan Africa, the primary mode of transmission is by contact with sex workers. Ratio F:M 13:1  In China, Myanmar (Burma), parts of Europe, IV drug use is the principal mode.  Thus, prevention rests on determination of mode of transmission.

Prevalence of HIV  In some countries in Africa, such as Botswana, HIV prevalence among adults is as high as 25 to 35 percent, with a drastic decrease in life expectancy.  Even in the United States, HIV prevalence averages 25% among men having sex with men (MSM), with the rate as high as 48% in some ethnic groups  Thus, sexual transmission is most common.

Major Problems  Although drugs are available, and effective, for the treatment of AIDS, there are major deficiencies. Among them are inadequate distribution to developing countries (high cost), requiring prolonged treatment (not curative), adverse drug reactions, development of drug resistance.  Primary prevention such as use of condoms and needle exchange have been advocated, but with varying results  Vaccine for primary prevention not yet available. Therapeutic vaccine for treatment is being explored.

Emergence of Infections  New infectious disease agents continue to emerge in populations throughout the world.  More than 30 agents have emerged during the past two decades.  Infectious diseases may also reemerge after a period of quiescence, e.g. tbc  May appear in a new locality, WN encephalitis, monkey pox  An agent may undergo genetic changes (e.g. influenza).

Emergence of Influenza  An agent of great concern globally is influenza virus.  Influenza virus is known to cause epidemics as early as the 1500’s, and pandemics have been described as early as  The most extensive pandemic ever known is the pandemic of influenza of , which killed more 20 million people.

Ref Business Week, April 14, 2003

Discovery of Influenza Virus  First isolated from a pig in 1931 (swine flu)  Isolated from human in 1933

Characteristics of Influenza Virus  Types A, B, C  Diameter nm  Pleomorphic, spherical, filamentous particles  Single-stranded RNA  Segmented genome, 8 segments in A and B  Hemagglutinin and Neuraminidase on surface of virion

Mechanisms of Transmission of Influenza Viruses  Aquatic birds  Pigs  Humans

Coping with Emerging Infections  During the past several years, the public as well as health professionals are keenly aware of the potential of global spread of emerging infectious diseases, particularly SARS, avian influenza.  Agencies such as WHO, CDC, NIH as well as Global Health Council, World Bank, Global Forum for Health Research are taking up the challenges of global health. Millions of dollars have been appropriated to meet these challenges.

Preparing for the next pandemic Are we ready for the next influenza pandemic? Many epidemiologists and virologists feel another pandemic of influenza is inevitable; the question is when.

Bioterrorism Similarly, use of biological agents to attack against civilian population is a likely possibility, the question is which agent; anthrax, smallpox, pneumonic plague?

Infectious Causes of Chronic Diseases  Helicobacter pylori: peptic ulcer  Hepatitis B & C: Hepatocellular ca  Human herpesvirus 8: Kaposi’s ca  Human papilllomavirus: cervical ca  Epstein-Barr virus: nasopharyngeal ca, Burkett’s lymphoma  Mycoplasma pneumoniae: coronary artery disease ?

suggested Reading  Anthony S. Fauci. Infectious diseases: Considerations for the 21st Century. Clinical Infectious Diseases. 2001:32: