The unseasonably warm weather of late should not lull us into complacency. Peak flu season is not far off. Sadly, it can take tragedy to prompt people to exercise vigilance. The death of a six-year-old boy from complications of influenza A at Tuen Mun Hospital serves to remind us of the dangers of seasonal flu. And three cases of H7N9 imported from the mainland are a reminder of even more lethal strains that could test the city’s defences, amid massive culls of poultry stocks in Japan and South Korea to contain the virus. Two cases caused the deaths of men aged 62 and 75.

The younger man’s case is a cautionary tale. Against medical advice, he discharged himself from a Dongguan hospital on Tuesday, two days after being admitted with fever and shortness of breath and returned to Hong Kong. He died in Yan Chai Hospital in Tsuen Wan on Friday after testing positive to H7N9. Exposure to poultry or wet markets remains the most likely origin of imported infections. The man’s death serves as a dire warning against risky behaviour as well as disregard for medical advice. Health minister Dr Ko Wing-man has appealed to visitors to affected mainland areas to stay away from wet markets. It is also important to practise good personal and food hygiene – especially thorough hand-washing – and to seek early treatment for fever or respiratory symptoms.

The loss of a child from a common community infection is difficult to accept. The parents of six-year-old Cheung Tsz-yui have been critical about how long it took to administer the anti-viral drug Tamiflu, but an expert has questioned whether it was appropriate for his acute condition or too late anyway. Our thoughts must be with the family. They will not be the last to suffer in this way. Unfortunately, even the best health care systems cannot avoid criticism of performance from time to time.