While most memories of the Sars outbreak in 2003 have faded with time, there is one word many people in the Pearl River Delta instantly associate with that time - vinegar.
When 20 people were approached at random in Guangzhou and asked what first comes to mind when they think about Sars, 15 said vinegar. Four mentioned the isatis root, a Chinese medicine rumoured to be useful against Sars and one mentioned civet cats, which hosted the Sars virus and transmitted it to humans.
They recall when there were reports of a mystery illness spreading but silence from the government. Rumours that vinegar fumes could ward off the disease took hold.
"I still remember my daughter calling me suddenly on the first working day after the Lunar New Year holiday that year," said Zhu Yinghua, a 61-year-old retired teacher.
"She sounded scared and urged me to shop for vinegar and medicine called roxithromycin [an antibiotic]."
"I still remember I was disapproving at first, but soon felt panic with my daughter crying on the phone and yelling 'Mum, people are dying in Guangzhou from an unknown but horrible disease … don't waste time. Just go buy some'," Zhu said.
"I soon found that my daughter was right. When I went to a supermarket, many people were already buying vinegar."
Drug stores began to run out of the isatis root, as prices soared from 6 yuan (HK$7.50) per 200 grams to 50 and even 80 yuan. Vinegar prices rocketed as speculators sought 100 yuan or more per bottle.
"The label price was meaningless in the panic buying," recalled Luo Bihua, a 35-year-old accountant. "It was so hard to buy even though you would pay 200 or 300 yuan."
Worried residents called relatives in other provinces or in Hong Kong to seek supplies.
According to Xinhua, salt sales in Beijing reached 7,247 tonnes from April 23-25, equal to 45 days of normal sales, as panic buying set in.
Now, locals look back on the panic buying with bemusement.
"To be honest, I can't believe I was so silly," said He Zhijian, a 65-year-old retired civil servant.
"I think ordinary people just did it to ease their fears when we were blocked from the truth [about the Sars outbreak]."