In 2025, Italy recorded a significant increase in cases of viruses transmitted to humans by mosquitoes. In particular, the Culex pipiens mosquito infected over 700 people, half of whom developed the most serious neuroinvasive form, which proved fatal in 69 cases.

In our country, this mosquito exists in two forms: Culex pipiens form molestus, which mainly bites humans in the evening and at night, and Culex pipiens form pipiens, which has a preference for birds.

For decades, evolutionary biologists believed that the molestus form had evolved over the last 200 years from the pipiens form in underground passages and cellars in northern Europe, so much so that they gave it the name “London Underground mosquito”. This case has often been cited as an example of a species' ability to adapt quickly to new environments and urbanisation. However, a new study led by researchers at Princeton University in the United States, with contributions from researchers at universities around the world, including Sapienza, refutes this theory.

The study – published on October 23 in the journal Science – thanks to the analysis of the DNA of thousands of Culex pipiens specimens representative of the geographical and genetic diversity of the species, shows that molestus evolved and adapted to humans between 1,000 and 10,000 years ago in an ancient agricultural society, most likely in Ancient Egypt, where it developed an adaptation to anthropised environments that in more recent times has allowed it to colonise underground environments in central and northern Europe.

‘In addition to reviewing one of the “textbook cases” on urban evolution and adaptation, the research also has important implications for public health,’ says Alessandra della Torre of the Department of Public Health and Infectious Diseases, co-author of the study, ‘and provides new information on the genetic variability of this mosquito that may be useful for better understanding the role of the species in the transmission of West Nile virus from birds to humans.  The results pave the way for more in-depth research on the potential links between urbanisation, hybridisation and virus transmission from birds to humans.

Ancient origin of an urban underground mosquito - Yuki Haba, PipPop Consortium, Petra Korlević, Erica McAlister, Mara K. N. Lawniczak, Molly Schumer, Noah H. Rose, and Carolyn S. McBride Authors Info & Affiliations – Science,  2025 -DOI: 10.1126/science.ady4515 

Further Information
Alessandra della Torre 
Department of Public Health and Infectious Diseases
alessandra.dellatorre@uniroma1.it

Beniamino Caputo
Department of Public Health and Infectious Diseases
beniamino.caputo@uniroma1.it