Temporary restriction zones brought in to help stem the spread of the bluetongue virus (BTV-3) now cover the whole of the South East after more cases were found.
The government announced on Saturday that 'high risk' and 'control' zones previously set up in the UK had been merged and extended.
It means the new restrictions cover all of Surrey, West Sussex and Greater London, and comes days after the Department for Environment, Food and Rural Affairs extended the zones to cover the whole of Kent and East Sussex.
A government spokesperson said: "Following reports of suspicion of clinical disease in sheep at premises in East Sussex and East Yorkshire the UK CVO [chief veterinary officer] has confirmed two new cases of BTV-3."
Lincolnshire, Cambridgeshire, Bedfordshire and Hertfordshire are all now included in the restricted zones, along with Norfolk, Suffolk, Essex, and East Yorkshire.
There are now 95 cases in the country of the the virus.
The government said the zones were extended "following the identification of cases close to the edge of the bluetongue restricted zone and in accordance with our policy of seeking to contain and slow the spread of disease".
The restricted zone was already beginning to have a financial impact on some farmers in South East of England.
The virus is not harmful to humans but can lead to blue, swollen tongues in animals, reduced birth rates and limited milk yields.
It is spread by midges that are often blown over from mainland Europe during spells of warm weather.
