THE EPIDEMIOLOGY OF VARICELLA-ZOSTER VIRUS INFECTIONS

In this investigation, a distinctive chickenpox model incorporating the Caputo fractional derivative is introduced. Equilibrium points and the fundamental reproduction number of the model are systematically computed. The study also scrutinizes the existence, uniqueness, positivity, and boundedness of solutions. Furthermore, a comprehensive analysis of both local asymptotic stability and global stability at the disease-free equilibrium is carried out. To demonstrate the practical utility of the model, a numerical simulation of chickenpox dynamics in Phuket city is conducted using MATLAB. This research contributes to a better understanding of chickenpox transmission dynamics, offering valuable insights for disease control and management strategies.

The aim of this study was to elucidate vaccine effectiveness (VE) during varicella outbreaks in schools and nurseries in Japan.

An outbreak was defined as emergence of three or more cases of varicella within 21 days at the same institute. Clinical information such as varicella vaccination status, and history of varicella was collected. If a child had varicella during the outbreak, information about absences, fever, and disease severity was collected.

From September 2018 to January 2020, four outbreaks were reported around our institute from three elementary schools and one nursery. A total of 676 children were analyzed in this study. Seventy-six children (11.2%) were unvaccinated, 309 (45.7%) had received one dose of vaccine, and 291 (43.0%) had received two doses. Most children in Pre-K2 (1–2 years old) to Pre-K6 (5–6 years old), who were the targets of the national immunization schedule, received two doses. Meanwhile, most children older than third grade received single dose. Seventy-five children (11.1%) had varicella. Varicella prevalence from Pre-K5 to the third grade was greater than 10%. The adjusted VEs of single- and two-dose of varicella vaccine were 57.8% and 89.0%. The number of days absent was significantly longer in unvaccinated children than single-dose recipients (P = 0.0145). Unvaccinated children had significantly more severe skin eruptions than single-dose recipients (P = 0.0046) and two-dose recipients (P = 0.0258).

Although VEs of single-dose varicella vaccination during outbreaks was not high, the VE of two-dose vaccination was similar to that in a previously reported case-control study.

Keratitis is one of the most prevalent ocular diseases manifested by partial or total loss of vision. Amongst infectious (viz., microbes including bacteria, fungi, amebae, and viruses) and non-infectious (viz., eye trauma, chemical exposure, and ultraviolet exposure, contact lens) risk factors, viral keratitis has been demonstrated as one of the leading causes of corneal opacity. While many viruses have been shown to cause keratitis (such as rhabdoviruses, coxsackieviruses, etc.), herpesviruses are the predominant etiologic agent of viral keratitis. This chapter will summarize current knowledge on the prevalence, diagnosis, and pathobiology of viral keratitis. Virus-mediated immunomodulation of host innate and adaptive immune components is critical for viral persistence, and dysfunctional immune responses may cause destruction of ocular tissues leading to keratitis. Immunosuppressed or immunocompromised individuals may display recurring disease with pronounced severity. Early diagnosis of viral keratitis is beneficial for disease management and response to treatment. Finally, we have discussed current and emerging therapies to treat viral keratitis.

From 2006 to 2011 nearly 174,000 deaths were prevented in Latin America and the Caribbean through vaccination of children under five, which is widely attributed to the Expanded Program on Immunization (EPI). Despite near global adoption of EPI recommendations, vaccination coverage shows substantial variation across world regions. Causes for low immunizations within regions are multifaceted and include vaccination program costs. To date, publications regarding vaccine coverage across Latin America and the Caribbean are not readily available. This study aimed to: (1) compare vaccine coverage trends across nations within the region; and (2) assess whether national immunization program expenditures are correlated with vaccine coverage.

Coverage for nine vaccines were collected by nation using publicly available data from WHO. National immunization program expenditures for each country were collected from the World Bank Index. The proportion of countries achieving 90% coverage in the years 2013 and 2017 for each vaccine were compared. Pearson correlation coefficients were calculated to measure the relationship between financing variables and DTP3 coverage for 2017.

In 2017, fewer Latin American and Caribbean nations were able to achieve 90% vaccine coverage for five vaccines compared to 2013. Mostly weak to moderate positive relationships were found between national immunization program expenditures and DTP3 coverage for 2017. Excluding Haiti, a weak negative relationship was found between total government expenditure on vaccines per infant and DTP3 coverage for 2017. Countries across Latin America and the Caribbean were largely self-reliant in funding vaccine expenditures.

Fewer countries across Latin America and the Caribbean are currently achieving optimum national vaccine coverage and weak to moderate relationships between routine immunization and vaccine expenditures and coverage were observed. Additional factors contributing to national vaccine coverage should be concomitantly examined to implement strategies which optimize delivery of childhood immunizations.