Takeaway: If the government shutdown resumed for a longer period of time than we just witnessed, we may have seen a reduction of operations at the USPTO.
As of now, the USPTO was not affected by the government shutdown. This is because the USPTO had previously built up financial reserves in case of a situation like this. With that said, because the USPTO is a part of the federal government, they may have to reduce their operations if the government shutdown resumes.
The USPTO made an announcement on January 24, 2019 indicating that they may run out of operational funds if the government shutdown resumed. The reason they would have run out of funds is not because they were not bringing in enough to operate, but rather, because they were not allowed to access funds that they had collected since the government began its shutdown in December. The USPTO is only allowed to use funds that were collected before a government shutdown began, which could have run out if the shutdown had continued.
If the USPTO were to shut down along with the other federal governmental agencies, they would have tried to remain operational in a limited capacity. The USPTO expected that they would continue to accept applications and maintain their information technology systems. This means that they would still collect fees and accept applications through their electronic filing systems.