To understand the disease geography of biological warfare, Việt Minh leaders needed to understand the biology of microbes. Accordingly they turned to information made available through their connections in China. Moreover they had to make detailed maps of the northern Vietnamese countryside. According to responses to surveys and other material received by the Committee to Prevent Germs from local authorities between April 1952 and March 1953, mostly from the local resistance committees (UBKCHC), the enemy launched:

• 42 attacks in Việt Bắc, largely coming by airplanes, but using cannon and spies as well;
• 17-18 attacks in Liên Khu III;
• 15-30 attacks in Khu Tả Ngạn, with most coming in February 1953;
• and, scattered attacks elsewhere.

Here is a breakdown of the province and number of reported incidents of French airplanes supposedly dropped strange things. A partial map of these sites is shown above.

• Phú Thọ, 12x
• Bắc Giang, 6x
• Cao Bằng, 4x
• Hải Ninh, 4x
• Lạng Sơn, 3x
• Vĩnh Phúc, 3x
• Tuyên Quang, 3x
• Yên Bái, 2x
• Thái Nguyên, 2x
• Bắc Ninh, 1x
• Hà Giang, 1x
• Quảng Yên, 1x