Sharad Malavade

A systematic review to identify areas of enhancements of pandemic simulation models for operational use at provincial and local levels

BackgroundIn recent years, computer simulation models have supported development of pandemic influenza preparedness policies. However, U.S. policymakers have raised several concerns about the practical use of these models. In this review paper, we examine the extent to which the current literature already addresses these concerns and identify means of enhancing the current models for higher operational use.MethodsWe surveyed PubMed and other sources for published research literature on simulation models for influenza pandemic preparedness. We identified 23 models published between 1990 and 2010 that consider single-region (e.g., country, province, city) outbreaks and multi-pronged mitigation strategies. We developed a plan for examination of the literature based on the concerns raised by the policymakers.ResultsWhile examining the concerns about the adequacy and validity of data, we found that though the epidemiological data supporting the models appears to be adequate, it should be validated through as many updates as possible during an outbreak. Demographical data must improve its interfaces for access, retrieval, and translation into model parameters. Regarding the concern about credibility and validity of modeling assumptions, we found that the models often simplify reality to reduce computational burden. Such simplifications may be permissible if they do not interfere with the performance assessment of the mitigation strategies. We also agreed with the concern that social behavior is inadequately represented in pandemic influenza models. Our review showed that the models consider only a few social-behavioral aspects including contact rates, withdrawal from work or school due to symptoms appearance or to care for sick relatives, and compliance to social distancing, vaccination, and antiviral prophylaxis. The concern about the degree of accessibility of the models is palpable, since we found three models that are currently accessible by the public while other models are seeking public accessibility. Policymakers would prefer models scalable to any population size that can be downloadable and operable in personal computers. But scaling models to larger populations would often require computational needs that cannot be handled with personal computers and laptops. As a limitation, we state that some existing models could not be included in our review due to their limited available documentation discussing the choice of relevant parameter values.ConclusionsTo adequately address the concerns of the policymakers, we need continuing model enhancements in critical areas including: updating of epidemiological data during a pandemic, smooth handling of large demographical databases, incorporation of a broader spectrum of social-behavioral aspects, updating information for contact patterns, adaptation of recent methodologies for collecting human mobility data, and improvement of computational efficiency and accessibility.

Re-emergence of cholera in the Americas: Risks, susceptibility, and ecology

Background: The re-emergence of cholera in Haiti has established a new reservoir for the seventh cholera pandemic which threatens to spread to other countries in the Americas. Materials and Methods: Statistics from this new epidemic are compared to the 1991 Peru epidemic, which demonstrated the speed and complexity with which this disease can spread from country to country. Environmental factors implicated in the spread of Vibrio cholerae such as ocean currents and temperatures, as well as biotic factors from zooplankton to waterfowl pose a risk for many countries in the Americas. Results: The movement of people and goods from Hispaniola are mostly destined for North America, but occur to some degree throughout the Americas. These modes of transmission, and the probability of uncontrolled community spread beyond Hispaniola, however, are completely dependent upon risk factors within these countries such as water quality and availability of sanitation. Although North America has excellent coverage of these deterrents to the spread of infectious gastrointestinal diseases, many countries throughout Latin America and the Caribbean lack these basic services and infrastructures. Conclusions: In order to curb the immediate spread of cholera in Hispaniola, treatment availability should be expanded to all parts of the island and phase II epidemic management initiatives must be developed.

Cholera in Ecuador: Current relevance of past lessons learnt

This report analyses the trends in the cholera epidemic that hit Ecuador in 1991. The study is based on personal experiences and analysis of epidemiological databases from the Ministry of Public Health of Ecuador. The number of cases and initial attack rates in an immunologically naive population are described by province. An analysis of the Andean and coastal cholera patterns of transmission are described along with its associated risk factors. The logistical, environmental, and socio-cultural risk factors prevalent during the epidemic and the control measures implemented are also reviewed. Also, the role of the epidemic in the development of the public health and healthcare resources in Ecuador is discussed here. Current data indicate favorable conditions for another outbreak of cholera in Ecuador. In view of the existing risk factors, new strategies are proposed to prevent such an epidemic in the future.

Reemergence of Measles in the Americas: The Genotype B3 2011–2012 Outbreak in Ecuador

This study characterizes a measles outbreak which occurred in Ecuador in 2011–2012, analyzing data from 3700 suspected cases of measles reported to Ecuador’s Ministry of Public Health. The study population had a large age range and included 333 confirmed cases of measles. The greatest number of cases were found in the <1 year (32.43%, n = 108) and 1–4 year (30.03%, n = 100) age-groups. Compared to Mestizos, indigenous people had the highest number of cases (68.2%, n = 227), as well as a higher risk of infection (OR 7.278 (CI 5.251–10.087)). The greatest protection from measles was observed in individuals who received two doses of the measles vaccine. Residents of Pastaza (OR 6.645 CI (3.183–13.873)) and Tungurahua (OR 8.346 CI (5.570–12.507)) had a higher risk of infection than the other provinces. Of the 17 laboratory confirmed cases, all were identified as genotype B3. Age-group, ethnicity, measles vaccinations, and residence in Tungurahua and Pastaza were correlated with rates of measles infection in the outbreak. Tungurahua and Pastaza, where the outbreak originated, have large indigenous populations. Indigenous children <1 year of age showed the highest incidence. It is likely that indigenous women do not have immunity to the virus, and so are unable to confer measles resistance to their newborns.

Overview of the Ophthalmic System

Drug delivery to the eye is a challenging task given the inherent structural and physiological uniqueness of the eye. The eye is a composite organ comprised of unique structures with distinct structure and functions that work together for the perception of sight. Structures like the cornea, the crystalline lens, and the vitreous humor are avascular structures, while the uveal tract is primarily the vascular layer of the eye. The retinal neuro-circuitry is complex and situated deep inside the eye and is a derivative of neuroectoderm. Similar to the blood–brain barrier, there is the blood–retina barrier in the eye. The limited external surface area and the deep isolated location of the different structures of the eye along with avascularity of some of the structures and the blood–retina barrier pose unique challenges for delivery of drugs to intraocular structures.