All the vertebrates in Australia including humans died off due to biopathogens. Insects are the highest life forms left in some parts of the world. Humans are durable by nature and have survived in certain isolated, sheltered enclaves. These enclaves are very overcrowded. They are filled with many people squeezed into small geographic areas and have little food available.
Conditions are harsh.
The health care system consists of only a few hospitals in each enclave to take care of numerous people. You live in Nexa, which is a small, overcrowded area of barely habitable land along the eastern coast of what was once a state called Texas. It used to be part of a large country called the United States. Nexa raises most of its food in greenhouses. Fish from the ocean are not eaten unless they are tested carefully.