October 2003

EMERGING DISEASES: GEOPOLITICAL, SOCIOECONOMIC, AND PUBLIC HEALTH TRENDS
By Saul B. Wilen, M.D.

Globalization

Globalization, technology, the “instantaneous” nature of international commerce, the advent of immediate communication, and rapid international travel and transport of people, plants, animals, and goods have all contributed to a world that functions as though it were shrinking in size. Globalization has resulted in increased dependence especially in the spheres of information, business, economics, and finance.

Urbanization

Population demographics relating to size, growth, density, geographic distribution, and economic patterns over the past five decades have supported urbanization as a progressive trend in the United States and the rest of the world. The dominance of developing core cities and surrounding areas has become the reality. These metropolitan areas whether large or small, increase in population at a steady pace. The consequences of urbanization include: encroachment of human populations with the geographic spread of cities at their periphery into areas that have been natural animal habitats; pollution and adverse environmental outcomes; the stretching of available necessary resources (water, clean air, food, sewage systems, healthcare, public safety and emergency services, and infrastructure for energy production and distribution/transmission, communication, educational facilities, and social services); and the increasing vulnerabilities of such population concentrations to disease, economic adversity, and even terrorism through its development out of frustration and helplessness, as a focus for its expression, and through the creation of a terrorist haven.

Dr. M. Perryman, a Texas-based economist has studied Texas population trends and shown these to reflect urbanization which parallels that seen in the U.S. and the rest of the world. As of 2002, about two-thirds of all Texans lived in the states six largest metropolitan areas. He has concluded that, “the Texas population will continue toward a metropolitan emphasis.”

Trends

Over the past few decades and especially in the last few years, changing patterns relating to human infectious diseases have emerged. SARS, Monkeypox, West Nile virus, Dengue fever, Plague, AIDS, Hanta viruses, and Lyme disease are prominent examples. Outbreaks of these diseases have occurred in unexpected geographic locations, at unexpected times of the year, and with unexpected severities. The American public in general is unaware of most of these diseases and Public Health professionals have done little to educate healthcare workers and the public about them.

SARS

This past year, 2002-2003, brought the emergence of SARS (Severe Acute Respiratory Syndrome) caused by a corona virus and spread human-to-human via droplet infection. The world outbreak began in Guangdong Province of mainland China in November 2002. The four month silence about the existence of the epidemic by the Chinese government until February 2003 played a significant role in the uncontrolled spread of the disease. Healthcare workers unwittingly played a significant role in the spread of SARS throughout the world, and closing healthcare facilities helped bring the epidemic under control. SARS infected 8439 people in thirty countries on five continents with a death rate of ten percent (812 people). In mainland China, more than 5300 people were infected and 349 died. The United States was not hard hit with only 75 cases and no deaths.

Public Health officials and healthcare workers struggle with understanding and controlling SARS, a disease that is both difficult to diagnose and difficult to treat. The illness was passed from person to person, the transmission became intensified when healthcare workers became infected, and “super spreaders”, people for unknown reasons are extremely contagious, infected hundreds.

In evaluating the SARS epidemic significant questions have been raised relating to the seasonal variation of SARS, the risk of household transmission (important since many patients were sent home for isolation and quarantine), evaluation for optimal diagnostic tools, the potential mutation of the corona virus that causes SARS, the existence of a SARS reservoir (as is the case for Influenza viruses) to support recurrence, and identification of potential “super spreaders.” These and other components of SARS experiences and processes can be used for the development of predictive modeling for recurrence, in modeling for future disease epidemics, and even for bio-terrorism and terrorism prevention planning.

Influenza

Strains of the Influenza virus return each year from embedded reservoirs, during the cold months. The WHO (World Health Organization) Influenza Surveillance Network serves as part of a global alert mechanism for the emergence of Influenza viruses especially those with pandemic potential. A pandemic can occur when a new virus appears against which humans have no immunity. With the existing increase in global transport, as well as urbanization and overcrowded conditions, new virus epidemics can quickly take hold around the world. This is the pattern seen in the recent SARS epidemic.

Vaccination is the principal strategy for preventing Influenza and reducing the impact of epidemics. Deaths from Influenza, approximately 36,000 each year in the United States, have increased over the past two decades, partly because of the aging of the population. It is important that the older and other at-risk populations prevent Influenza by taking the vaccination against it yearly. However, the present vaccination rate is only about thirty percent in the U.S.

HIV/AIDS

AIDS (acquired immunodeficiency syndrome) cases were first reported in the U.S. in 1981 and the human devastation in the 1980s was rampant. New medications have allowed Americans to become complacent about safe sex and a new generation of gay men have reached their 20’s without the experience and direct memory of the graphic early AIDS consequences and death rate. This new generation has not benefited from early prevention strategies. Socioeconomic factors – homophobia, high rate of poverty and unemployment, and lack of access to healthcare by racial/ethnic minorities – create barriers to HIV testing, diagnosis, and treatment. Increased risk taking has resumed. Many myths about safe sex have emerged among young heterosexual individuals that are used to justify unprotected sex practices.

In North America there are 980,000 people living with HIV/AIDS. New medication development which is solely treatment, in the mid-1990s helped control AIDS allowing HIV-infected people to live longer and reduced U.S. deaths from 51,000 in 1995 to about 15,000 in 2001. The development of a viable HIV/AIDS vaccine for prevention has been elusive for the past 10 to 12 years. New data released in late July, 2003 indicate that AIDS diagnoses in the United States have increased for the first time in ten years. Similar findings are reflected in the August 22, 2003 health report from the San Antonio Metropolitan Health District.

Urgent priorities remain. Prevention initiatives that link to treatment and care programs, and reach at-risk populations for early diagnosis and treatment must be expanded. Learning from HIV/AIDS experiences of the past two decades and establishing globally linked programs can still keep the pandemic from worsening.

Mosquito Vectors

A number of human diseases are spread by mosquito vectors. Included are Dengue fever, Malaria, Yellow fever, West Nile virus, and filariasis. The spring and early summer rains of 2003 have enhanced the breeding grounds for mosquitoes. The rainfall has also made it harder to control them because pesticides become diluted with each new cloud burst. The cool wet weather delayed the development process with more time for growth through the larval stage into the adult form. The result is bigger and hungrier mosquitoes by the time the weather gets hot and dry and they begin to fly. This has been the case for this summer.

Dengue Fever

Dengue fever and Dengue hemorrhagic fever are caused by four closely related, but antigenically distinct virus serotypes. Infection with one of the serotypes does not render cross-protective immunity. However, until the late 20th century each of the serotypes remained primarily in its endemic region. The introduction of additional serotypes and mosquito vectors into various regions has resulted in the human population now being at risk for two or more Dengue infections. Dengue has emerged as a major public health problem in the region consisting of the Americas. No Dengue vaccine is available. In 1997 it was determined that the geographic distribution of the mosquito vector has progressively widened. Dengue is presently the most important mosquito-borne viral disease affecting humans, with a case-fatality rate of five percent. Most of the deaths occur among children and young adults.

West Nile Virus

Though West Nile virus was first found in Uganda in 1937, its progression in the United States, identified first in New York in 1999, has generated great interest and concern. The initial failure of U.S. health officials to quickly identify West Nile virus exposed weaknesses in America’s ability to detect emerging infectious diseases that occur elsewhere and are then transported to the U.S. In that year (1999) only four states were affected, with 62 cases and seven deaths. By 2002, West Nile was present in forty states. There were 4156 cases and 284 deaths making the U.S. outbreak of West Nile Encephalitis the largest reported in the world. West Nile has proven to be extremely aggressive and versatile.

The occurrence of dying and dead birds in a community should be of concern to the residents. All communities should be educated to be alert to such occurrences and to report such findings to local health authorities immediately. These birds can be retrieved for testing. The results may serve as an early warning sign of a possible health problem. Mosquito collections can then be instituted to determine if any are carrying the West Nile virus.

No medical treatment or vaccine presently exists. Since 1999 health officials have tried – mosquito spraying and other control efforts, public information messages, and disease detection programs – to slow the rapid spread of the disease.

CDC is recommending in the states where the virus has been found, the use by the public of mosquito repellents containing DEET, the removal of standing water, repair of screens, clothing that protects by covering the arms, legs, and midriff, and to avoid the times of day (morning and evening) when mosquitoes are most active. Communities need to work to prevent mosquitoes from breeding and biting.

Emerging Diseases

Human living environments particularly in the western United States, have encroached into traditional animal habitats. The Hanta viruses have crossed over from being infections solely carried by the deer mouse, to ones infecting humans.

The level of vaccination of children for measles in Britain has steadily dropped to below 80 percent (from 92 percent in 1995) due to parental decisions against vaccinations over fear of side effects. Britain is experiencing more frequent and larger outbreaks of measles. The declining level of protection of the British population is declining and could result in measles becoming endemic.

Lyme disease (named in 1977) is the most commonly reported vector-borne disease in the United States. It has emerged and has become embedded in a geographic distribution (the northeast, mid-Atlantic, upper north-central regions, and northwestern California) with progressive infection of humans manifesting an acute and/or chronic form of the disease. This is an infectious disease transmitted by an arthropod (the deer tick) and causes more than 16,000 cases in the United States each year. An effective vaccine was developed and produced, but abandoned in February, 2002, by the nation’s only approved manufacturer, citing lack of demand for the vaccine. Strategies to prevent Lyme disease require education about the potential risks of the public who reside in and/or visit endemic areas. Prevention approaches include: avoiding tick habitats, wearing protective clothing and using repellents to avoid tick attachment, promptly removing attached ticks, and employing community measures to reduce tick abundance.

During a period of six weeks in June through July, 2003, a mosquito-borne viral meningoencephalitis killed 110 children in southern India. The cases have been among poor and malnourished children living in rural areas at the periphery of villages near bodies of stagnant water. This encephalitis according to the WHO is endemic to Asia with about 50,000 cases each year. Of concern is that this outbreak occurred several months earlier than expected and has a case-fatality rate of 55 percent, significantly higher than the 30 percent with previous occurrences.

In the spring of 2003, an outbreak of Monkeypox occurred in Wisconsin, Illinois, and Indiana. This represents the first outbreak of Monkeypox infection in the Northern Hemisphere. Human Monkeypox is a rare viral disease that occurs in central and West Africa. Animal species (non-human primates, rabbits, and some rodents) are susceptible to Monkeypox virus. The virus is transmitted to humans from infected animals, in this case imported sick African prairie dogs and a Gambian giant rat.

The bacteria that cause Plague have been detected in squirrels that inhabit national parks in the western states of the U.S. Areas of some parks have been closed due these infected rodents. Of concern is the potential for transmission of the bacteria to the western rat population as the fist step in establishing a cycle for infection of humans.

Specialists and Experts

Specialists and experts must be well grounded in the factual elements. For truth to prevail scientists, Public Health and healthcare professionals must bring to light the crucial and related ancillary facts. These must include the limitations of the science employed and the extent to which the opinions generated represent subjectivity, causality, and validity. These experts must be willing to include the public in the education and surveillance programs for early detection and intervention.