Cumulative Infected Cases Research Articles

A SICA compartmental model in epidemiology with application to HIV/AIDS in Cape Verde

We propose a new mathematical model for the transmission dynamics of the human immunodeficiency virus (HIV). Global stability of the unique endemic equilibrium is proved. Then, based on data provided by the “Progress Report on the AIDS response in Cape Verde 2015”, we calibrate our model to the cumulative cases of infection by HIV and AIDS from 1987 to 2014 and we show that our model predicts well such reality. Finally, a sensitivity analysis is done for the case study in Cape Verde. We conclude that the goal of the United Nations to end the AIDS epidemic by 2030 is a nontrivial task.

Characteristics of an epidemic outbreak with a large initial infection size

ABSTRACTA deterministic model proposed in previous literatures to approximate the well-known Richards model is investigated. However, the model assumption of small initial value for infection size is released in the current manuscript. Taking the advantage of the closed form of solutions, we establish the epidemic characteristics of disease transmission: the outbreak size, the peak size and the turning point for the cumulative infected cases. It is shown that the usual disease outbreak threshold condition (the basic reproduction number is greater than unity) fails to fully guarantee the existence of peaking time and turning point when the initial infection size is not relatively small. The epidemic characteristics not only depend on but also on another index, the net reproduction number.

Modeling the effect of comprehensive interventions on Ebola virus transmission.

Since the re-emergence of Ebola in West Africa in 2014, comprehensive and stringent interventions have been implemented to decelerate the spread of the disease. The effectiveness of interventions still remains unclear. In this paper, we develop an epidemiological model that includes various controlling measures to systematically evaluate their effects on the disease transmission dynamics. By fitting the model to reported cumulative cases and deaths in Guinea, Sierra Leone and Liberia until March 22, 2015, we estimate the basic reproduction number in these countries as 1.2552, 1.6093 and 1.7994, respectively. Model analysis shows that there exists a threshold of the effectiveness of isolation, below which increasing the fraction of latent individuals diagnosed prior to symptoms onset or shortening the duration between symptoms onset and isolation may lead to more Ebola infection. This challenges an existing view. Media coverage plays a substantial role in reducing the final epidemic size. The response to reported cumulative infected cases and deaths may have a different effect on the epidemic spread in different countries. Among all the interventions, we find that shortening the duration between death and burial and improving the effectiveness of isolation are two effective interventions for controlling the outbreak of Ebola virus infection.

The cascade of care in the Eastern European country of Georgia.

Individual and public health benefits of antiretroviral therapy (ART) rely on successful engagement of HIV-infected patients in care. We aimed to evaluate the HIV care continuum in the Eastern European country of Georgia. The analysis included all adult (age ≥ 18 years) HIV-infected patients diagnosed in Georgia from January 1989 until June 2012. Data were extracted from the national HIV/AIDS database as of 1 October 2012. The following stages of the HIV care continuum were quantified: HIV infected, HIV diagnosed, linked to care, retained in care, eligible for ART and virologically suppressed. Of 3295 cumulative cases of adult HIV infection reported in Georgia, 2545 HIV-infected patients were known to be alive as of 1 October 2012, which is 52% of the estimated 4900 persons living with HIV in the country. Of the 2545 persons diagnosed with HIV infection, 2135 (84%) were linked to care and 1847 (73%) were retained in care. Of 1446 patients eligible for ART, 1273 (88%) were on treatment and 985 (77%) of them had a viral load <400 HIV-1 RNA copies/mL. Overall, 39% of those diagnosed and 20% of those infected had a suppressed viral load. The findings of our analysis demonstrate that the majority of patients diagnosed with HIV infection are retained in care. Loss of patients occurs at each step of the HIV care continuum, but the major gap is at the stage of HIV diagnosis. Reducing the number of persons living with undiagnosed HIV infection and simultaneously enhancing engagement in continuous care will be critical to achieve maximum individual and public health benefits of ART.

Modelling strategies for controlling SARS outbreaks

Severe acute respiratory syndrome (SARS), a new, highly contagious, viral disease, emerged in China late in 2002 and quickly spread to 32 countries and regions causing in excess of 774 deaths and 8098 infections worldwide. In the absence of a rapid diagnostic test, therapy or vaccine, isolation of individuals diagnosed with SARS and quarantine of individuals feared exposed to SARS virus were used to control the spread of infection. We examine mathematically the impact of isolation and quarantine on the control of SARS during the outbreaks in Toronto, Hong Kong, Singapore and Beijing using a deterministic model that closely mimics the data for cumulative infected cases and SARS-related deaths in the first three regions but not in Beijing until mid-April, when China started to report data more accurately. The results reveal that achieving a reduction in the contact rate between susceptible and diseased individuals by isolating the latter is a critically important strategy that can control SARS outbreaks with or without quarantine. An optimal isolation programme entails timely implementation under stringent hygienic precautions defined by a critical threshold value. Values below this threshold lead to control, but those above are associated with the incidence of new community outbreaks or nosocomial infections, a known cause for the spread of SARS in each region. Allocation of resources to implement optimal isolation is more effective than to implement sub-optimal isolation and quarantine together. A community-wide eradication of SARS is feasible if optimal isolation is combined with a highly effective screening programme at the points of entry.

Surgical repair of traumatic medial disruption of the elbow in competitive athletes.

Five active athletes with acute medial elbow rupture were treated with muscle-ligamentous repair and a spiked washer. All patients regained full strength as well as stability of the elbow, and resumed previous sporting activities within 3 months of surgery. Early surgical repair of the ligament and flexor mass should be considered for active athletes who exhibit gross instability of the elbow on a valgus stress test without anaesthesia.