Shanghai was relatively unaffected by the worldwide ransomware attack over the weekend.

Yesterday, the city’s gas stations, stock exchange, entry-exit administration, hospitals and universities were working normally. However, security experts were warning people returning to work to be cautious and take precautions.

Hospitals and the stock exchange escaped the effects of the virus as they separate their core databases from public Internet networks while systems at places such as gas stations and entry-exit administrations had been restored yesterday.

Though more than 4,500 computers in Chinese universities had been affected, none of the computers at the city’s Jiao Tong University were hit, according to Jiang Kaida, who is in charge of information security at the university.

Wang Dong, chief information officer at Shanghai’s Zhoupu Hospital, said China’s hospital systems are specially designed with a “safety box” which separates the core patient and hospital database from external networks.

PetroChina, whose online payment system didn’t work at some gas stations during the weekend, has now restored the service nationwide, the oil giant said yesterday.