Chinese surveillance shows steep declines in reported vector-borne diseases during COVID-19

Reported incidence and mortality from five vector-borne diseases were substantially lower in China during 2020–2023 than in the preceding period, according to an analysis of surveillance data spanning 2004–2023. Compared with 2013–2019, overall reported incidence during 2020–2023 was 59.86% lower (95% CI: –60.36% to –59.36%; P < 0.001), while reported mortality was 83.72% lower (95% CI: –87.86% to –78.18%; P < 0.001). The observational analysis did not establish that COVID-19-related public-health measures alone caused these reductions.

The study examined typhus, dengue, leishmaniasis, malaria and epidemic encephalitis B, abbreviated EEB. Researchers obtained province- and age-specific surveillance data for 2004–2020 from the Chinese Center for Disease Control and Prevention and national aggregate data for 2021–2023 from the National Health Commission. Consequently, spatial and age-specific analyses covered 2004–2020, whereas national trend analyses extended through 2023. Across the earlier surveillance period, incidence and mortality declined significantly, with especially large reductions for malaria, dengue and EEB. Spatial hotspots were concentrated mainly in southern provinces, although the available data did not permit comparable geographic and age-specific analysis for 2021–2023.

Malaria and EEB had the largest reductions during the pandemic-period comparison, whereas typhus and leishmaniasis changed less markedly. These findings describe reported disease burden rather than experimentally measured causal effects. The analysis used Joinpoint regression to assess annual trends, seasonal-trend decomposition using STL to examine monthly seasonal patterns, and interrupted time-series analysis to evaluate monthly changes after January 2020. Seasonal autoregressive integrated moving average, or SARIMA, models trained on pre-COVID data also estimated expected monthly trajectories for 2020–2023, allowing observed pandemic-era patterns to be compared with forecasts based on earlier data.

Despite the size of the national reductions, interpreting them as a direct consequence of the COVID-19 period would be too simplistic, the researchers said. The observed changes may reflect a combination of pandemic-era public-health measures, the pre-existing long-term decline, disease-specific control programs and possible disruption to surveillance and reporting. The analysis therefore identifies a strong temporal association between the COVID-19 period and lower reported incidence and mortality, but it does not quantify the contribution of each possible factor. This distinction is particularly important because the study combines provincial and age-specific data through 2020 with national aggregate data for the final three years.

The findings underline the need for reliable surveillance and reporting during public-health emergencies, as well as forecasting tools that can be adapted when conditions change. The study does not show that the observed declines persisted independently of pandemic-era conditions or that they were produced by any single intervention. Instead, it documents a marked reduction in reported vector-borne disease burden in China, while leaving unresolved how much of the change reflected intervention effects, continuing control programs, underlying trends or changes in the completeness of health reporting.

Subject of Research: Trends in reported vector-borne disease incidence and mortality in China, 2004–2023

Article Title: Temporal trends in reported vector-borne diseases in China before and after the onset of COVID-19 from 2004 to 2023

Article References: Lei, Z., Liu, Q., & Lei, Z. (2026). Temporal trends in reported vector-borne diseases in China before and after the onset of COVID-19 from 2004 to 2023. PLOS Neglected Tropical Diseases, 20(10), e0014745. https://doi.org/10.1371/journal.pntd.0014745

Image Credits: AI Generated

DOI: 10.1371/journal.pntd.0014745

Keywords: vector-borne diseases, China, COVID-19, surveillance, malaria, dengue, leishmaniasis, epidemic encephalitis B, time-series analysis, public health, Temporal, trends