Hong Kong sits at a crossroads: travelers bring in tropical diseases, while the local climate is governed by global cycles. In the archive, this work sits alongside studies that view epidemics as waves in time: some distinguish outbreaks by their rhythm, others model the city as an organism with dengue fever, and still others assess the burden on hospitals. Our article stands with them but shifts the focus: it does not just describe the wave of one disease but seeks a shared pulse in two different ailments and a climate index.
The researchers collected monthly data on Guillain–Barré syndrome and dengue cases in Hong Kong from 2000 to 2016 from open sources at the local health center. Meteorological indicators (temperature, humidity, evaporation, and others) came from the Hong Kong Observatory, and the global MEI index from the U.S. National Oceanic and Atmospheric Administration. First, they calculated Spearman correlations between the diseases and weather, then shifted the series by various lags to find the maximum cross-correlation. To assess the dengue–MEI link, they built a Poisson regression with lags from 0 to 11 months. Finally, they applied wavelet analysis with the Morlet wavelet to see how the synchrony of oscillations changed over time rather than being constant.
Both diseases became more frequent in Hong Kong: Guillain–Barré notably increased after 2014, and imported dengue rose sharply from 2012. Their seasonal peaks are opposite: paralysis peaks in February–March, fever in August–September. The association with weather is weak but statistically significant for Guillain–Barré: colder and lower evaporation correspond to more cases (correlation coefficient around −0.28). Dengue and MEI are more strongly linked: the index explains more than 12% of dengue variability, with maximum correlation at a lag of 3–5 months. Between dengue and Guillain–Barré, no direct link is apparent, but at a seven-month shift the correlation reaches 0.28. Wavelet analysis showed that from 2005 to 2015, oscillations of dengue and Guillain–Barré periodically resonated, especially in years of major dengue outbreaks (2002, 2007, 2010, 2014).
Unlike neighboring studies that treat one disease or one city as an isolated system, this work is the first to show at the population level a non-stationary oscillatory link between dengue and Guillain–Barré syndrome. Previously, such a sequence was known only from clinical descriptions of individual patients. Now it is clear that the link is not constant but flares up in certain periods that coincide with large dengue waves. This changes the perspective: Guillain–Barré can be seen not as random background noise but as an echo of tropical epidemics reaching the subtropics with a delay.
The topic could develop toward multi-regional comparisons: taking several cities in Southeast Asia and southern China would test how universal the seven-month lag is and how local mosquitoes, population density, and travel flows affect it. Another path is to add data on Zika virus and other triggers of Guillain–Barré to separate the contribution of dengue from other infections. Also promising is building predictive models that, based on MEI and imported dengue, warn in advance of a possible rise in paralyses.
The results could help public health services in Hong Kong and neighboring regions plan neurology department resources in seasons following dengue outbreaks. They are also useful for epidemiologists studying how global climate cycles drive infection–complication chains.
The next step is to collect similar series from several cities and check whether the seven-month delay between dengue and Guillain–Barré holds under different conditions. Then, data on residents' travel and the source of imported dengue cases should be included in the model.
The work addresses a long-standing problem in epidemiology: how to distinguish causation from mere coincidence of rhythms when both diseases depend on a common external factor (climate). Wavelet coherence shows that the link is not constant but occurs episodically, yet it does not prove that dengue causes Guillain–Barré at the population level. The question of mechanism remains unresolved: what specific immune or viral processes turn a dengue wave into a wave of paralyses after seven months.
Guillain–Barré syndrome is named after two French neurologists who described it in 1916, while dengue fever has been known in China since ancient times as "water fever" because joint pain feels like bones breaking.
In Greg Bear's novel "Blood Music," an infection acts as a conductor, making the body's cells sing in unison. Here, dengue and Guillain–Barré also resonate, but not directly; rather, through a shared climatic rhythm, like two parts in one score.