"Suspicious" powder was reported on a Germany-Brazil flight
Several European countries have introduced new measures to tackle chemical or biological attack, while pointing out that they anticipate isolated cases at most.
Doctors have been reminded how to diagnose and treat anthrax, the disease at the centre of a US bio-terror scare, which has triggered several false alarms in Europe.
The UK says it has obtained extra supplies of the antiobiotics used to treat anthrax, while French Health Minister Bernard Kouchner indicated on Sunday that France was also seeking to increase its stocks.
He added: "We are not the only people seeking them."
No cure
Mr Kouchner said there would be no mass smallpox vaccination programme - the stockpiles would be used vaccinate people living around an infected person if a case occurred.
Some experts fear that smallpox reportedly manufactured by the Soviet Union in the 1980s for biowarfare may have leaked into the wrong hands.
In the aftermath of the US attacks:
France has launched a 400 million franc ($57m) programme dubbed Biotox to address risks, detect attacks against air or water and assess the country's capacity for decontamination. A military decontamination centre has been made available for civilian use.
Italy has boosted production of relevant drugs, and opened a 24-hour hotline at the Health Ministry. Rapid response teams have been formed, and test laboratories earmarked. Anthrax and smallpox are listed as category A threats; the full list includes botulism and ebola.
The UK has been refining plans to deal with a public health emergency. New supplies of anthrax antibiotics have been obtained, and doctors have been reminded how to recognise the disease.
Germany says it is establishing a biological warfare centre in Berlin to collect information on the threat and prevention of attacks. The Defence Ministry has denied reports that it has ordered an extra two million units of anthrax vaccine. However, the head of the German body responsible for tackling infectious diseases, Reinhardt Kurth, has said there is a shortage of vaccines against anthrax and other diseases.
Switzerland has opened a hotline to its biological and chemical weapons research laboratory to cope with a growing number of requests for information.
Belgium has embarked on a campaign to raise awareness in the health sector of a number of infectious diseases.