Seasonal Dynamics of Varicella Incidence in Bulgaria

Todorova, Tatina T.

doi:10.2217/fvl-2020-0012

Cited by 3 publications

(3 citation statements)

References 19 publications

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“…Both relative and absolute search query volumes for varicella keywords during the 5 years preceding the COVID-19 pandemic displayed seasonal variation in countries without UVV, peaking in the autumn or winter and in the spring. This pattern aligns with seasonal variation reported in studies of incident varicella infections and varicella-related hospitalizations from several European countries [1,19,[23][24][25][26][27][28][29]. Using data from Bulgaria as a comparator, we quantitatively evaluated clinical varicella incidence with the Google Trends Index, finding an adjusted R 2 value of 0.75.…”

Section: Plos Onesupporting

confidence: 76%

Impact assessment of immunization and the COVID-19 pandemic on varicella across Europe using digital epidemiology methods: A descriptive study

et al. 2023

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Background Varicella is usually a mild disease in children but may be life-threatening, especially in adolescents and adults. Infection control measures implemented during the Coronavirus Disease 2019 (COVID-19) pandemic may have suppressed varicella transmission, potentially creating an ‘immunity debt’, particularly in countries without universal varicella vaccination. Objectives To assess trends in Google search engine queries for varicella keywords as a proxy for varicella infection rates and to evaluate the effect of universal varicella vaccination on these trends. A further objective was to assess the impact of the COVID-19 pandemic on varicella keyword search query trends in countries with and without universal varicella vaccination. Methods This study used the keyword research tool, Google Trends, to evaluate trends in time series of the relative search query popularity of language-specific varicella keywords in 28 European countries from January 2015 through December 2021. The Google Ads Keyword Planner tool was used to evaluate absolute search volumes from March 2018 through December 2021. Results The relative search query popularity of varicella keywords displayed marked seasonal variation. In all 28 countries, the relative search query popularity of varicella keywords declined after the start of the COVID-19 pandemic (March 2020), compared with pre-pandemic levels (range, -18% to -70%). From April 2020 to July 2021, a period of intense COVID-19 transmission and infection control, absolute search volumes for varicella keywords were lower than pre-pandemic levels but rebounded after July 2021, when infection control measures were relaxed. Conclusion This evaluation of search query trends demonstrated that search query data could be used as a proxy for trends in varicella infection rates and revealed that transmission of varicella may have been suppressed during the COVID-19 pandemic. Consideration should be given to using search query data to better understand the burden of varicella, particularly in countries where surveillance systems are inadequate.

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Section: Plos Onesupporting

confidence: 76%

Impact assessment of immunization and the COVID-19 pandemic on varicella across Europe using digital epidemiology methods: A descriptive study

et al. 2023

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“…26,27 In tropical climates, chickenpox has a more distinct seasonal patternwith cases occurring in spring and winter -compared to temperate climates where cases occur throughout the year with lowest case counts during summer months. 24,[28][29][30][31] Across all climatic zones, temperature and rainfall contribute to the seasonality of disease. 32,33 A modelling study of chickenpox dynamics in Mallorca, a Mediterranean island, found that solar radiation and water vapor pressure were climatic drivers of chickenpox seasonality, with peaks in case numbers in June.…”

Section: Seasonality and Climatic Drivers Of Chickenpoxmentioning

confidence: 99%

“…While cases tend to be inversely related with temperature, even in temperate climate zones, consistent caseloads throughout the year are more commonly experience in temperate climate zones relative to tropical zones. [29][30][31] In contrast to the Elliniko outbreak, the larger of two outbreaks in Malakasa camp and the outbreak in Raidestos reflect expected seasonality of chickenpox, with higher incidence of cases in cooler seasons. Specifically, the larger of two outbreaks in Malakasa camp occurred from December 2016 -May 2017, with case counts staying consistently lower after February 2017.…”

Section: Seasonalitymentioning

confidence: 99%

Chickenpox Outbreaks in Three Refugee Camps on Mainland Greece, 2016-2017: A Retrospective Study

Scales,

Park,

Nixon

et al. 2023

Prehosp. Disaster med.

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Introduction: Displaced populations face disproportionately high risk of communicable disease outbreaks given the strains of travel, health care circumstances in their country of origin, and limited access to health care in receiving countries. Study Objective: Understanding the role of demographic characteristics in outbreaks is important for timely and efficient control measures. Accordingly, this study assesses chickenpox outbreaks in three large refugee camps on mainland Greece from 2016 – 2017, using clinical line-list data from Médecins du Monde (MdM) clinics. Methods: Clinical line-list data from MdM clinics operating in Elliniko, Malakasa, and Raidestos camps in mainland Greece were used to characterize chickenpox outbreaks in these camps. Logistic regression was used to compare the odds of chickenpox by sex, camp, and yearly increase in age. Incidences were calculated for age categories and for sex for each camp outbreak. Results: Across camps, the median age was 19 years (IQR: 7.00 - 30.00 years) for all individuals and five years (IQR: 2.00 - 8.00 years) for cases. Males were 55.94% of the total population and 51.32% of all cases. There were four outbreaks of chickenpox across Elliniko (n = 1), Malakasa (n = 2), and Raidestos (n = 1) camps. The odds of chickenpox when controlling for age and sex was lower for Malakasa (OR = 0.46; 95% CI, 0.38 - 0.78) and Raidestos (OR = 0.36; 95% CI, 0.24 - 0.56) when compared Elliniko. Odds of chickenpox were comparable between Malakasa and Raidestos (OR = 1.49; 95% CI, 0.92 - 2.42). Across all camps, the highest incidence was among children zero-to-five years of age. The sex-specific incidence chickenpox was higher for males than females in Elliniko and Malakasa, while the incidence was higher among females in Raidestos. Conclusion: As expected, individuals five years of age and under made up the majority of chickenpox cases. However, 12% of cases were teenagers or older, highlighting the need to consider atypical age groups in vaccination strategies and control measures. To support both host and displaced populations, it is important to consider risk-reduction needs for both groups. Including host communities in vaccination campaigns and activities can help reduce the population burden of disease for both communities.

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Impact of climate on varicella distribution in Bulgaria (2009-2018)

Todorova

2024

Cent Eur J Public Health

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Seasonal Dynamics of Varicella Incidence in Bulgaria

Cited by 3 publications

References 19 publications

Impact assessment of immunization and the COVID-19 pandemic on varicella across Europe using digital epidemiology methods: A descriptive study

Impact assessment of immunization and the COVID-19 pandemic on varicella across Europe using digital epidemiology methods: A descriptive study

Chickenpox Outbreaks in Three Refugee Camps on Mainland Greece, 2016-2017: A Retrospective Study

Impact of climate on varicella distribution in Bulgaria (2009-2018)

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