LASHKAR GAH, Afghanistan — In a large swath of the Taliban heartland in southern Afghanistan, government centers are facing a long-dormant concern this winter: Four years after the American troop surge helped make such places relatively secure, they are back under threat from the insurgents.

The fighting in Helmand Province in the south has been particularly deadly, with over 1,300 security force members killed between June and November. And the insurgents’ siege of several key districts has continued long after the traditional end of the fighting season.

It has been so bad that the 90-bed hospital for war wounded run in the provincial capital, Lashkar Gah, by the international aid group Emergency was still running nearly full in early December, according to Emanuele Nannini, the group’s coordinator. While the group keeps no statistics on how many of its patients are fighters, and treats all sides, a rough estimate is that half of the patients are Afghan police officers, from both national and local forces. Soldiers are treated in military hospitals, which do not divulge their statistics.

“This year is much worse than previous years,” said Dr. Abdul Hamidi, a police colonel who is head of medical services for the national police in Helmand. “We’ve heard that the Quetta Shura has a big push to raise their flags over three districts by January, and has ordered their people to keep fighting until they do,” he said, referring to the exiled Taliban leadership council in Pakistan.