Acid Fly or Paederus Dermatitis Among Foreign Medical Students Residing in Institutional Hostels in Rangpur, Bangladesh

Background:
Paederus dermatitis is a form of irritant contact dermatitis triggered by
pederin, a toxin released when rove beetles are crushed against the skin.
Outbreaks of this condition are frequently observed in residential
institutions, particularly during rainy seasons.
Objective:
The study utilized line-listing to summarize cases by person, place, and
time, supplemented by environmental walk-through assessments to
identify risk factors.
Methods:
We performed a descriptive cross-sectional study of an outbreak among
foreign medical students residing in three hostels at Rangpur
Community Medical College (RCMC) in Bangladesh, covering the
period from January to December 2025.
Results:
A total of 76 clinical cases and 79 attack episodes were identified. The
majority of affected students were Nepalese (34/76) and Indian (33/76),
and female students accounted for 40 of the 76 cases. Clustering was
evident at the room level, with 13 rooms reporting two or more cases,
and 91.1% (72/79) of attack episodes occurred during the monsoon
months of July and August. Among 74 cases with available risk-factor
data, the most frequently documented associated factors were seasonal
occurrence during the monsoon (72/74, 97.3%), sleeping with windows
open (59/74, 79.7%), shared exposure within rooms (49/74, 66.2%),
crushing the insect on the skin (48/74, 64.9%), and bed placement near
windows (42/74, 56.8%).
Conclusion:
The outbreak demonstrated strong seasonality and room-level
clustering. Preventing future occurrences requires synchronized
environmental management and student awareness strategies
intensified during the monsoon.