Florida Red Tides, Manatee Brevetoxicosis, and Lung Models.

In 1996, 149 Florida manatees, Trichechus manatus latirostris, died along the southwest coast of Florida. Necropsy pathology results of these animals indicated that brevetoxin from the Florida red tide, Karenia brevis, caused their death. A red tide bloom had been previously documented in the area where these animals stranded. The necropsy data suggested the mortality occurred from chronic inhalation and/or ingestion. Inhalation theories include high doses of brevetoxin deposited/stored in the manatee lung or significant manatee sensitivity to the brevetoxin. Laboratory models of the manatee lungs can be constructed from casts of necropsied animals for further studies; however, it is necessary to define the breathing pattern in the manatee, specifically the volumes and flow rates per breath to estimate toxin deposition in the lung. To obtain this information, two captive-born Florida manatees, previously trained for husbandry and research behaviors, were trained to breathe into a plastic mask placed over their nares. The mask was connected to a spirometer that measured volumes and flows in situ. Results reveal high volumes, short inspiratory and expiratory times and high flow rates, all consistent with observed breathing patterns.

Back-projection and sensitivity analysis of the HIV-AIDS epidemic in the Caribbean

In this study we estimated past human immunodeficiency virus (HIV) incidence in 19 nations in the primarily English-speaking Caribbean and projected the course of the epidemic to the year 1999. We compared the results obtained from several different models of HIV incidence and different assumed incubation distributions. Linear and nonlinear optimization methods were used to fit several models (power, logistic, spline and step) to adult (age 15 years or older) AIDS incidence data derived from our existing surveillance system. All four models tested gave good fits to the data, with estimates of cumulative HIV incidence in 1993 ranging from 16,504 to 21,732. An increase in the assumed median of the AIDS incubation distribution by one year increased the estimates of current cumulative adult HIV incidence by approximately 12 percent; these estimates varied by as much as 6 percent between models. An adjustment of the data for possible reporting delay increased the estimates by approximately 7 percent and for underreporting by 25 percent. Despite their sensitivity to underlying assumptions, back-projection estimates provide useful insights into the patterns of HIV and AIDS incidence. The models indicate that HIV and AIDS incidences in the English-speaking Caribbean have been rising steadily, with adult HIV prevalence in the general population still less than 1 percent(AU)

Modelos para el estudio de la epidemia del SIDA en el Caribe de habla inglesa / Modellings the HIV/AIDS epidemic in the English-speaking Caribbean

En este estudio se examinan los efectos pasados y las posibles repercusiones futuras de la infección por el virus de la inmunodeficiencia adquirida en 19 países del Caribe de habla inglesa. Para contrastar dos hipótesis sobre la prevalencia de la infección por el virus de la inmunodeficiencia humana, se empleo el modelo DemProj de proyección demográfica. En la hipótesis de valores bajos, la prevalencia del virus de la inmunodeficiencia humana en los adultos se estabiliza en 2 por ciento en el año 2000 y en la de valores altos, en 5 por ciento. En el año 2010, la incidencia anual del síndrome de inmunodeficiencia adquirida excede los 11 000 y 28 000 casos en una y otra hipótesis respectivamente. En ambas, 70 por ciento de los casos son adultos jóvenes de 20 a 45 años y 12 por ciento, niños de 0 a 15 años. La mortalidad aumenta a más del doble entre los 20 y los 40 años en la hipótesis de valores bajos y a más del cuádruple en la de valores altos. El efecto en las tasas de mortalidad es tambien severo para los niños de 0 a 10 años. Los costos totales anuales de la epidemia se acercarán a US$ 500 millones (en US$ constantes de 1989) o a 2 por ciento del producto interno bruto en la hipótesis de valores bajos y US$ 1 200 millones o 5 por ciento del producto interno bruto en la de valores altos

Modeling the HIV/AIDS epidemic in the English speaking Caribbean

The study reported here examines the past and potential future impact of HIV/AIDS in 19 nations of the primarily English-speaking Caribbean. The authors use DemProj, a demographic projection model, to explore two different HIV scenarios. In the low scenario adult HIV prevalence stabilizes at 2 percent in the year 2000, and in the high scenario adult HIV prevalence stabilizes at 5 percent. By the year 2010, annual AIDS incidence exceeds 11,000 cases in the low scenario and 28,000 in the high scenario. In both scenarios 70 percent of the cases are in the young adults 20-45 years old and 12 percent are in children 0-15. Age-specific mortality is more than doubled in the 20-40 age range in the low scenario and more than quadrupled in the high scenario. The impact on death rates is also severe among children 0-15. In assessing the economic impact, the authors estimate that the total annual costs of the epidemic will approach US$ 500 million (in constant 1989 US$) or 2 percent of GDP in the low scenario, and will exceed US$ 1,200 million or 5 percent of gdp in the high scenario. (AU)

Modeling the HIV/ AIDS epidemic in the English speaking Caribbean

The study reported here examines the past and potential future impact of HIV/AIDS in 19 nations of the primarily English-speaking Caribbean. The authors use DemProj, a demographic projection model, to explore two different HIV scenarios. In the low scenario adult HIV prevalence stabilizes at 2 percent in the year 2000, and in the high scenario adult HIV prevalence stabilizes at 5 percent. By the year 2010, annual AIDS incidence exceeds 11 000 cases in the low scenario and 28 000 in the high scenario. In both scenarios, 70 percent of the cases are in young adults 20-45 years old and 12 percent are in children 0-15. Age specific mortality is more than doubled in the 20-40 age range in the low scenario, and more than quadrupled in the high scenario. The impact on death rates is also severe among children 0-10. In assessing the economic impact, the authors estimate that the total annual costs of the epidemic will approach US$ 500 million (in constant 1989 US$) or 2 percent of GDP in the low scenario, and will exceed US$ 1 200 million or 5 percent of GDP in the high scenario

Back-projection of the HIV/AIDs epidemic in the Caribbean - abstract

In this study, we estimated past HIV incidence in 18 English-speaking Caribbean countries and Suriname, and projected the course of the epidemic to the year 2000. Nonlinear optimization methods were used to fit various models to adult (age 15 years or older) AIDS incidence data (not adjusted for bias in reporting) derived from our existing surveillance system. APM, an AIDS projection model, was used to project the future impact. The best feasible fit to the data was obtained by estimating adult HIV incidence as at with a=538.6 and b=0.6313. With this model, in 1992 adult HIV incidence reached 2586 (0.06 percent) and adult HIV prevalence 17272 (0.39 percent). This prevalence estimate is supported by recent blood donor and antenatal clinic data. The model predicts that by the year 2000 adult HIV incidence will reach 3569 (0.0796) and adult HIV prevalence 30,938 (0.61 percent). However, this does not negate the possibility of a recent upswing in incidence, as suggested by data from certain high-risk groups. Further work, including population sampling and additional modelling, is in progress to investigate these trends (AU)

Modelos para el estudio de la epidemia del SIDA en el Caribe de habla inglesa / Modellings the HIV/AIDS epidemic in the English-speaking Caribbean

En este estudio se examinan los efectos pasados y las posibles repercusiones futuras de la infección por el virus de la inmunodeficiencia adquirida en 19 países del Caribe de habla inglesa. Para contrastar dos hipótesis sobre la prevalencia de la infección por el virus de la inmunodeficiencia humana, se empleo el modelo DemProj de proyección demográfica. En la hipótesis de valores bajos, la prevalencia del virus de la inmunodeficiencia humana en los adultos se estabiliza en 2 por ciento en el año 2000 y en la de valores altos, en 5 por ciento. En el año 2010, la incidencia anual del síndrome de inmunodeficiencia adquirida excede los 11 000 y 28 000 casos en una y otra hipótesis respectivamente. En ambas, 70 por ciento de los casos son adultos jóvenes de 20 a 45 años y 12 por ciento, niños de 0 a 15 años. La mortalidad aumenta a más del doble entre los 20 y los 40 años en la hipótesis de valores bajos y a más del cuádruple en la de valores altos. El efecto en las tasas de mortalidad es tambien severo para los niños de 0 a 10 años. Los costos totales anuales de la epidemia se acercarán a US$ 500 millones (en US$ constantes de 1989) o a 2 por ciento del producto interno bruto en la hipótesis de valores bajos y US$ 1 200 millones o 5 por ciento del producto interno bruto en la de valores altos

Se publica en inglés en el Bull. PAHO Vol. 28(3), 1994

Modeling the HIV/ AIDS epidemic in the English speaking Caribbean

The study reported here examines the past and potential future impact of HIV/AIDS in 19 nations of the primarily English-speaking Caribbean. The authors use DemProj, a demographic projection model, to explore two different HIV scenarios. In the low scenario adult HIV prevalence stabilizes at 2 percent in the year 2000, and in the high scenario adult HIV prevalence stabilizes at 5 percent. By the year 2010, annual AIDS incidence exceeds 11 000 cases in the low scenario and 28 000 in the high scenario. In both scenarios, 70 percent of the cases are in young adults 20-45 years old and 12 percent are in children 0-15. Age specific mortality is more than doubled in the 20-40 age range in the low scenario, and more than quadrupled in the high scenario. The impact on death rates is also severe among children 0-10. In assessing the economic impact, the authors estimate that the total annual costs of the epidemic will approach US$ 500 million (in constant 1989 US$) or 2 percent of GDP in the low scenario, and will exceed US$ 1 200 million or 5 percent of GDP in the high scenario

This article will be published in Spanish in the BOSP. Vol. 117(4), October 1994

A model of the transmission of dengue fever with an evaluation of the impact of ultra-low volume (ULV) insecticide applications on dengue epidemics

We have developed a deterministic susceptible, exposed, infectious, resistant or removed (SEIR) model of dengue fever transmission that enables us to explore the behavior of an epidemic, and to experiment with vector control practices. Populations of both host and vector are divided into compartments representing disease status (susceptible, exposed, infectious, and , for humans, resistant), and the flow between compartments is described by differential equations. Examination of the equilibrium points leads to a formulation of the basic reproduction rate (Zo) of the dsease. With a base set of parameters, Zo=1.9 and the model realistically reproduces epidemic transmission in an immunologically naive population. Control of adult mosquitoes by ultra-low volume (ULV) aerosols is simulated by an abrupt decrease in vector densities, followed by gradual recovery of the vector population. The model indicates that ULV has little impact on disease incidence, even when multiple applications are made, although the peak of the epidemic may be delayed. Decreasing the carrying capacity of the environment for mosquitoes, and thus the basic reproduction rate of the disease, by source reduction or other means, is more effective in reducing transmission. (AU)