A flu virus is sweeping through families in Marlborough, a Blenheim doctor says.
Hospitals and GPs across the Nelson Marlborough health district have seen more patients with flu-like illness.
The district health board's clinical director of medical services, Dr Bruce King, said there had been several confirmed cases of the H1N1 influenza infection in young people - the same strain which caused the 2009 swine flu pandemic.
One patient has been admitted to Nelson Hospital's intensive care unit and required prolonged mechanical ventilation.
"A number of patients have been admitted acutely with breathing difficulties from infections, many of which are presumed to be viral in origin," King said.
The elderly and those with pre-existing lung conditions are at greatest risk of influenza, he said.
Scott Street Health GP and the board's chief medical officer for primary health, Dr Ros Gellatly, said viral illnesses were reported across whole families, making the school holidays miserable.
Blenheim's Community pharmacy pharmacist, Debbie Carter, said that she had seen a "dramatic increase" in the number of flu patients in the past two weeks.
"We have seen whole families affected, as well as the young right through to the elderly."
Unichem Mortimer's & Fraser's Pharmacy pharmacist Hannah Arnott said most patients coming to the pharmacy showed cold symptoms but there were a number of "nasty cases of flu" and the cold weather had aggravated asthma cases.
Those with a health complication have until July 31 to get the free flu jab.
Those at high risk of complications, including pregnant women, people aged 65 and over, and anyone with long-term health conditions such as heart disease, stroke, diabetes, respiratory disease (including asthma), kidney disease and most cancers are eligible.
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