"is most widespread" is a correct and usable phrase in written English.
You can use it to refer to something that is happening or existing in many places, or that is affecting many people. For example, "Climate change is most widespread in the southern hemisphere."
It is most widespread and apparently most virulent in China, Vietnam, Hong Kong and Singapore, and the World Health Organization issued a global health alert last month.
Her worry is that figures are much higher and rising because child mortalities in isolated highland areas where disease is most widespread are unlikely to have been recorded.
But more than three in four acid attacks are against women, Mr. Shah said, and the practice is most widespread in societies where women have limited rights.
Bribery is most widespread in poorer, badly run parts of the world in Africa and the Middle East: the highest rates are reported in Sierra Leone (84%), Liberia (75%) and Yemen (74%).
By contrast, the misconception that markets will take care of themselves is most widespread at the top of the cycle, at the point of most danger to the system.
Almost every day, two C-17 Globemaster cargo planes take off from Ramstein Air Base in Germany carrying as many as 34,000 packets, each filled with two vegetarian meals, to be dropped from 20,000 feet onto the remotest regions of Afghanistan, especially those where hunger is most widespread.
But it is in Germany that retaliation appears to have been most widespread and concerted.
The flu virus continually mutates, and each spring, the C.D.C. chooses the strains it believes will be most widespread the following winter.
Adding covers to phones was most widespread in Seoul and Kampala, and the use of decorative phone straps was most popular in Seoul and Tokyo.
