Based on the text, please give me a brief summary of the history of the DTES neighbourhood in Vancouver

Around the beginning of the 20th century, the DTES was Vancouver's political, cultural and retail centre. Over several decades, the city centre gradually shifted westwards, and the DTES became a poor neighbourhood,[1] although relatively stable. In the 1980s, the area began a rapid decline due to several factors, including an influx of hard drugs, policies that pushed sex work and drug-related activity out of nearby areas, and the cessation of federal funding for social housing. By 1997, an epidemic of HIV infection and drug overdoses in the DTES led to the declaration of a public health emergency. As of 2018, critical issues include opioid overdoses, especially those involving the drug fentanyl; decrepit and squalid housing; a shortage of low-cost rental housing; and mental illness, which often co-occurs with addiction.

The DTES has transformed from the focal point of Vancouver’s cultural and commercial life at the start of the 20th Century to an impoverished neighbourhood with many socio-economic problems by the 1980s. Since the 1990s, the DTES has been home to a public health emergency due to drug overdoses, HIV infection, a housing crisis, and mental health problems.