A viral infection has killed 30 people in Ukraine.
The illness begins as an ordinary bout of flu, but after a week the symptoms get worse.
Almost 40,000 Ukrainians have contracted the disease. Around 100 are in hospital.
In the west of the country there has been a run on virus inhibitors and surgical masks. Schools and childcare centres in the city of Lvov are closed.
Test are being carried out to establish what kind of virus is causing the sickness. The H1N1 virus which causes Mexican flu has been ruled out.