What happened
The Global Health Security Agenda, built up after the 2014–2015 West African Ebola epidemic exposed how slowly outbreaks were detected and reported, put American epidemiologists inside the health ministries and disease-control agencies of countries judged most likely to be the source of the next pandemic — China chief among them, given its history with SARS in 2003 and its opacity around domestic outbreak reporting. Congress had funded this at roughly $600 million; when that money ran out in 2019, the Trump administration chose not to request its renewal, and CDC warned it might have to shrink the programme from 49 countries to just 10.
The clearest individual casualty of that decision was Dr. Linda Quick, CDC's resident adviser to China's Field Epidemiology Training Program. She left her post in July 2019 after being told the position would be eliminated that September. CDC's total US-based staff working on global health security in China fell from 8 in March 2019 to 3 by December; local Chinese staff supporting the same work fell from 39 to 11.
CDC has stated the elimination of Quick's specific post "had absolutely nothing to do" with the agency's later slowness in learning about the Wuhan outbreak. That may be true of the formal notification chain — but the position existed precisely to give US officials real-time, on-the-ground visibility into a country whose government has a well-documented history of suppressing early outbreak information, and it was gone by the time that exact scenario played out again. It is worth noting Congress restored much of the CDC's broader emerging-disease budget after the administration proposed cutting it by 10–20% across 2018–2020, so the picture is one of a specific, targeted staffing gap rather than a wholesale defunding of CDC.