Epidemiology of varicella in Mexico

Impact of seasonality and ambient temperature on testicular torsion incidence: A Mexican Nationwide population-based study

INTRODUCTION

Testicular torsion is a surgical emergency characterized by twisting the spermatic cord, disrupting blood flow, and causing severe pain and swelling. It predominantly affects males aged 12 to 18, with an incidence of about 3.8 per 100,000 in this age group. Immediate surgical intervention is vital, as irreversible damage can occur within 4-6 h of symptom onset. Recent studies have suggested a correlation between low ambient temperatures and an increased incidence of testicular torsion, particularly in colder months.

OBJECTIVE

This study aims to analyze the relationship between temperature variations, seasonal trends, and testicular torsion incidence in Mexico from 2014 to 2024.

MATERIAL AND METHODS

A retrospective cohort study was conducted using a hospital admissions database from Mexico, covering December 2013 to July 2024. Patients diagnosed with testicular torsion (ICD-10 code N44X) aged 1 year or older were included, resulting in 3973 admissions after exclusions. ANOVA was used for seasonal difference analysis, and the Kruskal-Wallis U test was employed to examine climatic regions. Post-hoc comparisons utilized Tukey's test for monthly incidence. The Spearman rank test evaluated the correlation between mean monthly temperatures and incidence. A heatmap displayed monthly incidence by state.

RESULTS

Significant seasonal variations in incidence rates were observed: averages were 0.07 ± 0.02 in winter, 0.05 ± 0.02 in spring, 0.04 ± 0.02 in summer, and 0.05 ± 0.02 in fall (p = 0.001). Seasonal fluctuations correlated significantly with ambient temperatures (p < 0.001). Post-hoc analysis indicated that winter incidence was notably higher than in other seasons (p < 0.05). Monthly incidence rates were similar in temperate and tropical regions (p = 0.095) but higher than in the subtropical zone (p < 0.05). A moderate negative correlation between ambient temperature and monthly incidence was found, strongest in subtropical regions (R = -0.323, p = 0.000).

DISCUSSION

The present work is the first to comprehensively examine the relationship between ambient temperature and testicular torsion incidence in Mexico, showing significant seasonal patterns. The findings align with previous research in Latin America, suggesting lower temperatures increase the risk of torsion. Public health initiatives are crucial to raising awareness and potentially improving early diagnosis and management strategies.

CONCLUSION

A clear association between seasonal temperature fluctuations and testicular torsion incidence was observed, particularly during winter months in Mexico.

Seroprevalence of antibodies against varicella zoster virus across all age groups during the post-COVID-19 pandemic period in Chonburi Province, Thailand

As of 2024, Thailand has not incorporated the varicella-zoster virus (VZV) vaccine into the Expanded Program on Immunization (EPI). This study aimed to evaluate VZV seroprevalence across all age groups in Chonburi Province, Thailand, during the post-COVID-19 era, and to support the development of a vaccination plan against VZV. A total of 950 participants were enrolled from October 2022 to January 2023. VZV antibody levels were measured using ELISA kits (EUROIMMUN, Lübeck, Germany), with seropositivity set at ≥110 IU/L. The overall VZV seropositivity rate was 64.8%, similar to rates in 1994 and 2014. However, seropositivity rates for the 5-9, 10-14, and 15-19 age groups were significantly higher in the 1994 study, and for the 10-14 and 15-19 age groups in the 2014 study, indicating a declining trend among young Thai individuals. The seropositivity rate increased with age, with a seroprevalence exceeding 80% in individuals aged 30 years and older. Our study found a significant association between the history of varicella and seropositivity. Thus, a positive history may indicate immunity. In conclusion, a significant portion of Thai adolescents are still vulnerable to varicella, highlighting the crucial role of vaccination in averting serious illness.

A time series study of the association between extreme temperature and ozone on varicella incidence

This study aimed to discuss the effects of extreme temperatures and ozone on the incidence of varicella in Shijiazhuang City from 2014 to 2022, which provides new ideas for preventing public health events. METHODS We collected varicella cases in Shijiazhuang, China, from 2014 to 2022 and evaluated the relationship between temperature extremes and ozone on varicella incidence by building distributional lag nonlinear models. The analysis was stratified by age and sex, with 19,188 varicella cases reported. A nonlinear "J"-shaped relationship emerged between mean daily temperature and varicella incidence, where colder temperatures heightened risk, while hotter ones reduced it, particularly affecting females and adolescents. Additionally, ozone concentration displayed an "S"-shaped correlation, with low levels posing a risk and high levels protective against varicella, notably among females and adults. Our study results show a significant correlation between extreme temperatures and ozone concentrations on varicella incidence, and this study may help prevention and control authorities to create timely warnings of high-risk outbreaks, and assist the public in responding to varicella outbreaks.

Risk factors for nonidiopathic and idiopathic facial nerve palsies: findings of a retrospective study

BACKGROUND

Idiopathic (IF) and nonidiopathic facial (NIF) nerve palsies are the most common forms of peripheral facial nerve palsies. Various risk factors for IF palsies, such as weather, have been explored, but such associations are sparse for NIF palsies, and it remains unclear whether certain diagnostic procedures, such as contrast agent-enhanced cerebral magnetic resonance imaging (cMRI), are helpful in the differential diagnosis of NIF vs. IF.

METHODS

In this retrospective, monocentric study over a five-year period, the medical reports of 343 patients with peripheral facial nerve palsy were analysed based on aetiology, sociodemographic factors, cardiovascular risk factors, consultation time, diagnostic procedures such as cMRI, and laboratory results. We also investigated whether weather conditions and German Google Trends data were associated with the occurrence of NIF. To assess the importance of doctors' clinical opinions, the documented anamneses and clinical examination reports were presented and rated in a blinded fashion by five neurology residents to assess the likelihood of NIF.

RESULTS

A total of 254 patients (74%) had IF, and 89 patients (26%) had NIF. The most common aetiology among the NIF patients was the varicella zoster virus (VZV, 45%). Among the factors analysed, efflorescence (odds ratio (OR) 17.3) and rater agreement (OR 5.3) had the highest associations with NIF. The day of consultation (Friday, OR 3.6) and the cMRI findings of contrast enhancement of the facial nerve (OR 2.3) were also risk factors associated with NIF. In contrast, the local weather, Google Trends data, and cardiovascular risk factors were not associated with NIF.

CONCLUSION

The findings of this retrospective study highlight the importance of patient history and careful inspections to identify skin lesions for the differential diagnosis of acute facial nerve palsy. Special caution is advised for hospital physicians during the tick season, as a surge in NIF cases can lead to a concomitant increase in IF cases, making it challenging to choose adequate diagnostic methods.

Delineating the Seasonality of Varicella and Its Association With Climate in the Tropical Country of Colombia

BACKGROUND

Varicella causes a major health burden in many low- to middle-income countries located in tropical regions. Because of the lack of surveillance data, however, the epidemiology of varicella in these regions remains uncharacterized. In this study, based on an extensive dataset of weekly varicella incidence in children ≤10 during 2011-2014 in 25 municipalities, we aimed to delineate the seasonality of varicella across the diverse tropical climates of Colombia.

METHODS

We used generalized additive models to estimate varicella seasonality, and we used clustering and matrix correlation methods to assess its correlation with climate. Furthermore, we developed a mathematical model to examine whether including the effect of climate on varicella transmission could reproduce the observed spatiotemporal patterns.

RESULTS

Varicella seasonality was markedly bimodal, with latitudinal changes in the peaks' timing and amplitude. This spatial gradient strongly correlated with specific humidity (Mantel statistic = 0.412, P = .001) but not temperature (Mantel statistic = 0.077, P = .225). The mathematical model reproduced the observed patterns not only in Colombia but also México, and it predicted a latitudinal gradient in Central America.

CONCLUSIONS

These results demonstrate large variability in varicella seasonality across Colombia and suggest that spatiotemporal humidity fluctuations can explain the calendar of varicella epidemics in Colombia, México, and potentially in Central America.

Effects of meteorological factors on the incidence of varicella in Lu'an, Eastern China, 2015-2020

Varicella (chickenpox) is a serious public health problem in China, with the most reported cases among childhood vaccine-preventable infectious diseases, and its reported incidence has increased over 20-fold since 2005. Few previous studies have explored the association of multiple meteorological factors with varicella and considered the potential confounding effects of air pollutants. It is the first study to investigate and analyze the effects of multiple meteorological factors on varicella incidence, controlling for the confounding effects of various air pollutants. Daily meteorological and air pollution data and varicella cases were collected from January 1, 2015, to December 31, 2020, in Lu'an, Eastern China. A combination of the quasi-Poisson generalized additive model (GAM) and distributed lag nonlinear model (DLNM) was used to evaluate the meteorological factor-lag-varicella relationship, and the risk of varicella in extreme meteorological conditions. The maximum single-day lag effects of varicella were 1.288 (95%CI, 1.201-1.381, lag 16 day), 1.475 (95%CI, 1.152-1.889, lag 0 day), 1.307 (95%CI, 1.196-1.427, lag 16 day), 1.271 (95%CI, 0.981-1.647, lag 4 day), and 1.266 (95%CI, 1.162-1.378, lag 21 day), when mean temperature, diurnal temperature range (DTR), mean air pressure, wind speed, and sunshine hours were -5.8°C, 13.5°C, 1035.5 hPa, 6 m/s, and 0 h, respectively. At the maximum lag period, the overall effects of mean temperature and pressure on varicella showed W-shaped curves, peaked at 17.5°C (RR=2.085, 95%CI: 1.480-2.937) and 1035.5 hPa (RR=5.481, 95%CI: 1.813-16.577), while DTR showed an M-shaped curve and peaked at 4.4°C (RR=6.131, 95%CI: 1.120-33.570). Sunshine hours were positively correlated with varicella cases at the lag of 0-8 days and 0-9 days when sunshine duration exceeded 10 h. Furthermore, the lag effects of extreme meteorological factors on varicella cases were statistically significant, except for the extremely high wind speed. We found that mean temperature, mean air pressure, DTR, and sunshine hours had significant nonlinear effects on varicella incidence, which may be important predictors of varicella early warning.

Understanding the Role of Environmental Transmission on COVID-19 Herd Immunity and Invasion Potential

COVID-19 is caused by the SARS-CoV-2 virus, which is mainly transmitted directly between humans. However, it is observed that this disease can also be transmitted through an indirect route via environmental fomites. The development of appropriate and effective vaccines has allowed us to target and anticipate herd immunity. Understanding of the transmission dynamics and the persistence of the virus on environmental fomites and their resistive role on indirect transmission of the virus is an important scientific and public health challenge because it is essential to consider all possible transmission routes and route specific transmission strength to accurately quantify the herd immunity threshold. In this paper, we present a mathematical model that considers both direct and indirect transmission modes. Our analysis focuses on establishing the disease invasion threshold, investigating its sensitivity to both transmission routes and isolate route-specific transmission rate. Using the tau-leap algorithm, we perform a stochastic model simulation to address the invasion potential of both transmission routes. Our analysis shows that direct transmission has a higher invasion potential than that of the indirect transmission. As a proof of this concept, we fitted our model with early epidemic data from several countries to uniquely estimate the reproduction numbers associated with direct and indirect transmission upon confirming the identifiability of the parameters. As the indirect transmission possess lower invasion potential than direct transmission, proper estimation and necessary steps toward mitigating it would help reduce vaccination requirement.

Association between ambient temperature and varicella among adults in Qingdao, China during 2008-2019

Little concern has been paid to the relationship between temperature and varicella among adults. Daily meteorological data and varicella cases in Qingdao among adults from 1 January 2008 to 31 December 2019 were collected. A combination of quasi-Poisson generalized additive model (GAM) and distributed lag non-linear model (DLNM) was conducted to assess the temperature-lag-varicella relationship. We also estimated the lag-response curves for different temperatures and the exposure-response relationships for different lag days. The number of varicella cases was 10,296. Compared with the minimum-varicella temperature (25°C), we found the largest effect of temperature on varicella within 21 lag days was at 1°C (RR, 6.72; 95% CI, 2.90-15.57), and then the effect declined as the temperature increased. A similar trend of rising first and then falling was found in temperature-response curves for different lag days. A reverse U-shape lag pattern was found for different levels of temperatures. Temperature may affect varicella.

The global disease burden of varicella-zoster virus infection from 1990 to 2019

Data of global epidemiology of varicella-zoster virus infection (VZVI) is limited. This study aimed to investigate the burden of VZVI based on the Global Burden of Disease Study 2019 data. The age-standardized rates, including the incidence, death, disability-adjusted life years (DALYs), and the estimated annual percentage changes (EAPC) of VZVI were calculated to evaluate the disease burden of VZVI. The global numbers of incident and death cases due to VZVI were 83,963,744 and 14,553, respectively. The age-standardized incidence rate of VZVI increased slightly all over the world, while the age-standardized death and DALYs rate decreased from 1990 to 2019 (EAPC = -2.31 and -1.61, respectively). The younger age (<5 years old) and older groups had the highest VZVI burden. The high sociodemographic index (SDI) region had the highest age-standardized incidence rates in 2019 (1236.28/100,000, 95% UI: 1156.66-1335.50) and the low SDI region had the lowest incidence (1111.24/100,000, 95% UI: 1040.46-1209.55). The age-standardized death and DALYs rate of VZVI decreased with the increase of SDI. Amongst the 21 geographical regions, the high-income Asia Pacific (1269.08/100,000) region had the highest age-standardized incidence rate in 2019, while Sub-Saharan Africa had the highest age-standardized death and DALYs rate. The global incidence of VZVI has continued to increase in the past three decades, while the age-standardized death and DALYs rates have decreased. More attention should be paid to the younger and older population, as well as low SDI regions. This article is protected by copyright. All rights reserved.

Budget impact analysis of multiple varicella vaccination strategies: a Mexico perspective

A number of live-attenuated varicella vaccines are produced globally that provide protection against the varicella zoster virus. In Mexico, varicella vaccination is not included in the national immunization program and is recommended for use only in high-risk subgroups. We developed a budget impact model to estimate the impact of universal childhood immunization against varicella on the national payer system in Mexico. A scenario of no varicella vaccination was compared to scenarios with vaccination with a single dose at 13 months of age, in alignment with the existing program of immunization with the measles-mumps-rubella vaccine. Nine different vaccination scenarios were envisioned, differing by vaccine type and by coverage. Varicella cases and treatment costs of each scenario were computed in a dynamic transmission model of varicella epidemiology, calibrated to the population of Mexico. Unit costs were based on Mexico sources or were from the literature. The results indicated that each of the three vaccine types increased vaccine acquisition and administration expenditures but produced overall cost savings in each of the first 10 years of the program, due to fewer cases and reduced varicella treatment costs. A highly effective vaccine at 95% coverage produced the greatest cost savings.

Burden of varicella in Latin America and the Caribbean: findings from a systematic literature review

BACKGROUND

Varicella is typically mild and self-limiting, but can be associated with complications and even death. The limited data available on varicella in Latin America and the Caribbean (LAC) indicate substantial burden in countries where varicella vaccine is not part of publicly funded childhood national immunization programs.

METHODS

A systematic literature review of published studies was complemented by "gray" literature on varicella incidence, complications, mortality, and economic consequences, in the absence and presence of universal varicella vaccination (UVV) in LAC.

RESULTS

Seroprevalence data indicate that varicella is usually a disease of childhood in LAC. Varicella incidence rates, while unreliable in the absence of mandatory reporting, show a trend to increased incidence due to greater urbanization and population density. The introduction of UVV in national immunization programs has led to significant reductions in varicella incidence in these areas.

CONCLUSIONS

Varicella continues to pose a substantial healthcare burden in LAC. The future introduction of UVV in additional countries is predicted to provide substantial reductions in cases, with important economic benefits. For countries that have already implemented UVV, the challenge is to maintain high rates of coverage and, where relevant, consider inclusion of a second dose to reduce breakthrough cases. Given the significant proportion of the region now implementing UVV, a regional recommendation in order to prevent any potential for age-shifts in varicella infection might be considered.

Digital epidemiology reveals global childhood disease seasonality and the effects of immunization

Public health surveillance systems are important for tracking disease dynamics. In recent years, social and real-time digital data sources have provided new means of studying disease transmission. Such affordable and accessible data have the potential to offer new insights into disease epidemiology at national and international scales. We used the extensive information repository Google Trends to examine the digital epidemiology of a common childhood disease, chicken pox, caused by varicella zoster virus (VZV), over an 11-y period. We (i) report robust seasonal information-seeking behavior for chicken pox using Google data from 36 countries, (ii) validate Google data using clinical chicken pox cases, (iii) demonstrate that Google data can be used to identify recurrent seasonal outbreaks and forecast their magnitude and seasonal timing, and (iv) reveal that VZV immunization significantly dampened seasonal cycles in information-seeking behavior. Our findings provide strong evidence that VZV transmission is seasonal and that seasonal peaks show remarkable latitudinal variation. We attribute the dampened seasonal cycles in chicken pox information-seeking behavior to VZV vaccine-induced reduction of seasonal transmission. These data and the methodological approaches provide a way to track the global burden of childhood disease and illustrate population-level effects of immunization. The global latitudinal patterns in outbreak seasonality could direct future studies of environmental and physiological drivers of disease transmission.

Association between the incidence of varicella and meteorological conditions in Jinan, Eastern China, 2012-2014

BACKGROUND

Varicella remains an important public health issue in China. In this study we explored the effect of weather conditions on the incidence of varicella in the temperate city of Jinan, Eastern China during 2012-2014 to inform public health prevention and control measures.

METHODS

Data on reported cases of varicella were obtained from National Notifiable Disease Report System. Meteorological data for the same time period were obtained from the Jinan Meteorological Bureau. A negative binomial regression model was used to assess the relationships between meteorological variables and the incidence of varicella. Given collinearity between average temperature and atmospheric pressure, separate models were constructed: one including average temperature without atmospheric pressure, the other including atmospheric pressure but without average temperature. Both models included relative humidity, wind velocity, rainfall, sunshine, and year as independent variables.

RESULTS

Annual incidence rates of varicella were 44.47, 53.69, and 46.81 per 100,000 for 2012, 2013, and 2014, respectively. Each increase of 100 Pa (hPa) in atmospheric pressure was estimated to be associated with an increase in weekly incidence of 3.35 % (95 % CI = 2.94-3.67 %), while a 1 °C rise in temperature was associated with a decrease of 3.44 % (95 % CI = -3.73-3.15 %) in the weekly incidence of varicella. Similarly, a 1 % rise in relative humidity corresponded to a decrease of 0.50 % or 1.00 %, a 1 h rise in sunshine corresponded to an increase of 1.10 % or 0.50 %, and a 1 mm rise in rainfall corresponded to an increase of 0.20 % or 0.30 %, in the weekly incidence of varicella cases, depending on the variable considered in the model.

CONCLUSION

Our findings show that weather factors have a significant influence on the incidence of varicella. Meteorological conditions should be considered as important predictors of varicella incidence in Jinan, Eastern China.

Varicella-Zoster Virus in Perth, Western Australia: Seasonality and Reactivation

Background

Identification of the factors affecting reactivation of varicella-zoster virus (VZV) largely remains an open question. Exposure to solar ultra violet (UV) radiation is speculated to facilitate reactivation. Should the role of UV in reactivation be significant, VZV reactivation patterns would generally be expected to be synchronous with seasonal UV profiles in temperate climates.

Methods

We analysed age and gender specific VZV notification time series data from Perth, Western Australia (WA). This city has more daily sunshine hours than any other major Australian city. Using the cosinor and generalized linear models, we tested these data for seasonality and correlation with UV and temperature.

Results

We established significant seasonality of varicella notifications and showed that while herpes-zoster (HZ) was not seasonal it had a more stable seasonal component in males over 60 than in any other subpopulation tested. We also detected significant association between HZ notifications and UV for the entire Perth population as well as for females and males separately. In most cases, temperature proved to be a significant factor as well.

Conclusions

Our findings suggest that UV radiation may be important for VZV reactivation, under the assumption that notification data represent an acceptably accurate qualitative measure of true VZV incidence.

The potential impact of climate change and ultraviolet radiation on vaccine-preventable infectious diseases and immunization service delivery system

Climate change and solar ultraviolet radiation may affect vaccine-preventable infectious diseases (VPID), the human immune response process and the immunization service delivery system. We systematically reviewed the scientific literature and identified 37 relevant publications. Our study shows that climate variability and ultraviolet radiation may potentially affect VPID and the immunization delivery system through modulating vector reproduction and vaccination effectiveness, possibly influencing human immune response systems to the vaccination, and disturbing immunization service delivery. Further research is needed to determine these affects on climate-sensitive VPID and on human immune response to common vaccines. Such research will facilitate the development and delivery of optimal vaccination programs for target populations, to meet the goal of disease control and elimination.

Systematic review of incidence and complications of herpes zoster: towards a global perspective

OBJECTIVE

The objective of this study was to characterise the incidence rates of herpes zoster (HZ), also known as shingles, and risk of complications across the world.

DESIGN

We systematically reviewed studies examining the incidence rates of HZ, temporal trends of HZ, the risk of complications including postherpetic neuralgia (PHN) and HZ-associated hospitalisation and mortality rates in the general population. The literature search was conducted using PubMed, EMBASE and the WHO library up to December 2013.

RESULTS

We included 130 studies conducted in 26 countries. The incidence rate of HZ ranged between 3 and 5/1000 person-years in North America, Europe and Asia-Pacific, based on studies using prospective surveillance, electronic medical record data or administrative data with medical record review. A temporal increase in the incidence of HZ was reported in the past several decades across seven countries, often occurring before the introduction of varicella vaccination programmes. The risk of developing PHN varied from 5% to more than 30%, depending on the type of study design, age distribution of study populations and definition. More than 30% of patients with PHN experienced persistent pain for more than 1 year. The risk of recurrence of HZ ranged from 1% to 6%, with long-term follow-up studies showing higher risk (5-6%). Hospitalisation rates ranged from 2 to 25/100 000 person-years, with higher rates among elderly populations.

CONCLUSIONS

HZ is a significant global health burden that is expected to increase as the population ages. Future research with rigorous methods is important.