Swine flu Q&A

Vaccines for swine flu are said to still be months away. Photo / Wanganui Chronicle

Herald health reporter Martin Johnston answers some of the questions people have been asking about swine flu.

How many people have been infected with swine flu?

In New Zealand, the number of confirmed cases since the virus arrived in April rose yesterday to 711, many of whom have recovered. Because testing of all potential cases has stopped, the number will be higher, but the Health Ministry's deputy director of public health, Dr Fran McGrath, said the ministry did not know how much higher.

The World Health Organisation's latest update, dated Monday, reports 70,893 confirmed cases worldwide, including 311 deaths.

How many people does the ministry expect will be infected?

Up to half the population. Nearly one-third may have no symptoms yet still be infectious.

How infectious is swine flu?

It is expected that every two people who get the infection will infect three others. This is slightly more infectious than seasonal flu viruses.

How severe is the illness?

For most who get symptoms, it is a mild to moderate illness. However, for some it is more serious and it is fatal for a small proportion.

Are any groups affected more than others?

Yes. In New Zealand, people of all ages have been affected, but the greatest number of cases has been in those aged up to the mid-20s.

A US-published study of Mexico at the peak of its swine flu in March and April, found that cases of illness and death from severe pneumonia were mainly among those aged 6 to 59.

Are any groups at greater risk of severe symptoms or complications?

Yes. Those with severe heart or lung disease, weakened immunity, pregnant women and young children. Some previously healthy people have also been severely affected.

Is the virus changing?

Dr McGrath said New Zealand laboratories had found no evidence of the virus mutating. She added that the mutation that had made the virus resistant to Tamiflu in a Danish patient this week, also made it unlikely to spread to other people.

When will there be a vaccine?

Vaccines are still said to be months away, and their use will depend on trials proving their safety and effectiveness. The ministry has an agreement to obtain pandemic flu vaccine from Melbourne-based manufacturer CSL.

How much anti-flu medicine does New Zealand have?

Before this outbreak began, the ministry had a stockpile of 1.25 million courses of Tamiflu and it later bought 125,000 of Relenza.

The ministry said fewer than 100 courses of Relenza had been used. It had "issued" around 34,000 courses of Tamiflu, including 10,000 that went to Pacific island nations, but the number used will not be known until next week.