Two Indicators, a Common Trend: Scabicide Dispensing and Search Volume as Indirect Proxies for Scabies in Spain (2021–2025)

Scabies is a highly contagious skin condition caused by a microscopic mite that burrows under the skin, causing intense itching and a rash. While it has been recognized for centuries as a significant health issue, it is classified by global health authorities as a neglected tropical disease, meaning it often receives less attention and funding than other illnesses. In many places, including Spain, scabies is not a "notifiable" disease, which means doctors are not required to report every single case to the government. This creates a blind spot for public health officials; without a mandatory reporting system, it is difficult to know exactly how many people are suffering or whether the number of cases is rising or falling. To fill this gap, researchers have begun looking for indirect clues, such as how many people are buying the medicines used to kill the mites or how often people type questions about the condition into search engines. These digital and pharmacy records act as a shadow of the actual disease, offering a way to track its movements even when official case counts are missing.

A team of researchers in Spain decided to test whether these indirect clues could reliably map the rise and fall of scabies over a five-year period. They focused on two specific types of data: the number of packages of scabies medication dispensed by pharmacies and the volume of searches people made on Google for scabies-related terms. The medicines they tracked were permethrin, a cream applied to the skin, and ivermectin, a pill taken by mouth. The study covered the years from 2021 through August 2025. By looking at these two streams of information side by side, the researchers hoped to see if they moved in sync and if they could reveal patterns that official health statistics might miss.

The results showed a clear and synchronized story. From 2021 through 2024, both the amount of medication sold and the number of online searches increased significantly. This upward trend suggested that the burden of scabies in Spain was growing during those years. However, the data from 2025 told a different story. In the first eight months of that year, the number of medication packages dispensed dropped compared to the same period in 2024, and the search activity also began to decline after peaking in 2023. While the researchers noted that this drop might signal a genuine decrease in cases, they cautioned that it was too early to be certain, as the year was not yet complete and other factors could be at play.

A striking feature of the data was the rhythm of the year. Both the medication sales and the search queries followed a predictable cycle, spiking dramatically during the winter months between December and March and falling to their lowest points during the summer. This seasonal pattern was so strong that the researchers had to use statistical methods to remove the winter peak from the data just to see the underlying trends clearly. Even after accounting for this seasonal cycle, the two indicators remained tightly linked. When people searched for information about scabies, it was almost always followed by an increase in people buying the medicine. In fact, the analysis suggested that changes in search activity often happened before changes in dispensing, hinting that online interest might serve as an early warning signal for a rise in cases.

The study also uncovered a shift in how doctors and patients were treating the condition. Over the five years, the ratio of oral ivermectin pills to topical permethrin creams changed dramatically. In 2021, permethrin was used far more often than ivermectin. By 2025, the use of ivermectin had risen so much that it was dispensed more frequently than the cream. This shift suggests that treatment habits are evolving, possibly because people or doctors feel the traditional cream is becoming less effective, though the study did not prove that the mites had become resistant to the drug. The researchers also noted that the decline in 2025 could be influenced by factors other than a drop in disease, such as changes in how people seek medical advice or a shift toward using artificial intelligence tools instead of traditional search engines.

Ultimately, the study concludes that tracking pharmacy sales and internet searches provides a powerful, complementary way to monitor scabies in countries where official case counts are unavailable. The two indicators moved together with such consistency that they validate each other as reliable proxies for the disease's presence. While the recent dip in 2025 offers hope that the situation may be improving, the researchers emphasize that continued observation is necessary to confirm whether this is a true turning point or just a temporary fluctuation. By watching these digital and commercial footprints, public health officials can gain a clearer, more timely picture of a disease that often goes uncounted.