Estimated reproduction ratio between herds per country in 2007. Estimate of the reproduction ratio for BTV between herds for different countries, based on the reported case date in 2007, and assuming an infectious period of 2 weeks per herd. In this year there was a secondary warm period in August, which is mirrored by a peak in the reproduction ratio for Germany and the Netherlands. The effect is less pronounced when longer infectious periods are assumed. The y-axis stops at 14. For higher values, the number of infected farms on which the estimate is based, is too small to be considered seriously. Especially in France where the epidemic had hardly started in 2006, the epidemic takes of later than in the other countries and only in September de the case numbers reach a sufficient number.