Scientists meeting in Rome have made important progress in identifying the role wild birds play in spreading the bird flu virus in Europe, according to a Swiss expert.
But Katharina Stärk, head of monitoring at the Federal Veterinary Office, said many questions remained unanswered and further research was needed.
Stärk was speaking on Wednesday at the end of a two-day conference held by the Food and Agriculture Organization (FAO) and the World Organisation for Animal Health.
The meeting, which was attended by around 300 scientists from over 100 countries, set out to fix the role played by wild birds in introducing bird flu into new areas. Scientists have been split on whether domestic poultry or wild birds are to blame.
"I think we all share the view that there are still a lot of questions that remain open, but for the first time there was no dispute about the fact that wild birds do have a role in the spread of the virus," Stärk told swissinfo.
"However, each country has to be looked at on a case-by-case basis. Wild birds may be relevant for the introduction of the virus in European countries, but in other countries that have different trade contacts and different levels of protection things might be different."
According to the FAO, wild birds are responsible for spreading the virus in Europe, a combination of domestic poultry and wild birds are to blame in Asia, whereas the poultry trade appears to be responsible in Africa.
"We need more coordination to bring together all the information in order to better understand and solve the puzzle," said Joseph Domenech, the FAO's chief veterinary officer.
With this in mind, the Federal Veterinary Office is to conduct research over the summer around Lake Constance – where the majority of Swiss bird flu cases have been found – to see whether wild birds that permanently live there carry the virus.
Stärk said the Swiss would also be examining research conducted in the Netherlands on how three species of duck common to Switzerland are susceptible to the virus and how they react to it.
"We have an ongoing screening programme at Lake Constance and I would expect an increased level of monitoring in the autumn when migratory birds that spend the winter in Switzerland arrive again," she said.
The veterinary office set up a nationwide screening programme in September last year as part of a Europe-wide initiative. Since then more than 1,000 wild birds have been tested.
Officials still maintain that the risk of infection from illegally imported live birds and poultry meat is greater than that from migratory birds.
The first case of bird flu in Switzerland was discovered on February 27 in Geneva. Since then there have been 32 cases of the deadly variant H5N1 among wild birds – the last on March 31.
The arrival of the virus in neighbouring countries at the beginning of February prompted the government to reintroduce a ban on keeping poultry outdoors. The order was lifted on May 1.
swissinfo, Adam Beaumont
From October 26 to December 16 last year, the autumn migration period, Switzerland banned the keeping of domestic poultry outdoors. The aim was to reduce the risk of Swiss poultry coming into contact with virus-carrying wild birds.
A second outdoor ban was imposed on February 20 after the H5N1 virus was detected in wild birds in neighbouring countries during the spring migration season.
Since introducing a nationwide screening programme in September last year, veterinary experts have taken samples from more than 1,000 wild birds.
According to latest World Health Organization figures, there have been 224 human cases of bird flu, including 127 deaths.
Most fatalities have occurred when humans have been in close contact with infected poultry. Health experts fear the H5N1 virus will eventually mutate into a form easily transmissible among humans, sparking a pandemic that could cost millions of lives.
In compliance with the JTI standards