Clamping down on travel raises questions of balance

Virtually closing down the country to control the spread of a bird flu pandemic might have "limited effectiveness", says a public health doctor.

Northland medical officer of health Dr Jonathan Jarman says this is because a flu virus can be spread even before infected people start coughing and sneezing.

That means the likely limited success of standard steps such as closing schools and other public gatherings and restricting travel "need to be balanced with the disruptive social and economic impacts of such measures".

He made these comments in a pandemic planning document for the Northland District Health Board that the Herald obtained under the Official Information Act.

New Zealand's 21 district health boards are producing pandemic plans in response to concern by the World Health Organisation that the H5N1 bird flu that has led to the deaths of millions of birds and 79 people in parts of Asia and Eastern Europe could mutate into a pandemic flu virus that spreads easily among humans, killing millions.

In a public health emergency such as a flu pandemic, the Government has wide powers to restrict contact between people and to close the borders.

"These things ... can interfere with people's individual freedoms," Dr Jarman told the Herald yesterday. "In public health we always have to balance those issues with the question: 'Is it going to work? Is it going to make a difference?"'

Christchurch virologist Dr Lance Jennings said yesterday that it usually took from 24 to 72 hours following infection with flu virus for people to start suffering symptoms such as fever, followed by headache, muscle pain, coughing and sneezing.

People could become infectious during that "incubation period".

"This is one of the issues with people being exposed [to a future pandemic flu] in a foreign country and getting on to a plane and arriving at their destination then going down with disease."

Dr Jarman said that once a flu pandemic began, the only intervention that would stop it was a vaccine. Restrictions on public gatherings and travel - designed to reduce the chances of virus transmission - would only slow the pandemic's spread.

"We are probably not going to have a vaccine [at first] and all we can do is slow down the transmission so that all the services that need to respond are not going to be overwhelmed all of a sudden.

"We also hope we can prevent transmission to some people so when we do get the vaccine we can vaccinate some people and be ready before the next wave comes."

The Government has a deal with Australian vaccine-maker CSL to supply a pandemic flu vaccine within four to six months of the World Health Organisation's declaration of a pandemic.

Dr Jennings said little research had been done on whether people spread the virus before symptoms started, but a study of flu in Taranaki found that did happen.

"We do know that people with symptoms are efficient transmitters. We don't know a lot about the transmission of human influenza virus during that early stage, the incubation period.

"There are a lot of unknowns but we mustn't let the unknowns negate what we do know. A common sense approach is to have those [public health] systems in place to deal with it."