I write this from what has been the dengue fever-gripped island of Cheung Chau, and, according to earlier reports, I must have been lucky to survive. Mass hysteria was triggered when it was reported that the number of people in Hong Kong to have contracted the mosquito-borne virus had risen to 26, and that nine of the cases were connected to Cheung Chau (those numbers later rising to 28 and 10).

The harbour-side area near the ferry pier, usually crammed with visitors during summer months, was almost deserted. One fish-ball vendor told me he had heard that the government would cancel all ferries and put the island into quarantine. His business was dead and he seemed more angry than ill.

As dengue fever scare hits Hong Kong, how can you avoid infection?

Government contractors could be seen dressed in white hazmat suits, ready for a full-scale chemical or biological holocaust, marching along streets and randomly spraying roadside vegetation with God knows what. There was no sign of the dreaded Aedes albopictus mosquito, but passing pedestrians were almost asphyxiated by the fumes.

A rumour disseminated on social media suggested the spray being deployed was a lethal version of a top-secret anti-mosquito formula that was dangerous to dogs. The first unverified mutt-death report arrived soon after, reaching me via WhatsApp.

But if a dog could die just from inhaling the gas, what were they using? Chlorine? A KGB-designed airborne variant of novichok?

Just when sensible reassurance was needed from the authorities, we were treated instead to classic scaremongering by the controller of public health. “The development [of the disease] on Cheung Chau is more worrying and not easy to predict,” Dr Wong Ka-hing told reporters, adding, “We expect there will be new cases in the near future.”

Panic ensued and it was just too much for some. On one social-media group, popular with French expatriates, a woman urged everyone to “leave Cheung Chau now, while there is still time” – and she wasn’t joking.

Ironically, the Hedley Environmental Index attributed to air-pollution levels in Hong Kong  more than 1,200 hospital visits and 18 deaths on the same day, but there were no reports of cancelled shopping trips to Tsim Sha Tsui.