Nebraska agriculture officials say no new cases of bovine tuberculosis have been found in three weeks of testing.

The latest results available show that roughly 1,200 cattle tested negative for the disease between June 29 and July 5. Including those tests, a total of 6,200 cattle have tested negative since two cases of bovine TB were found in a Rock County herd.

As of Sunday, 26 herds in 13 north-central and eastern Nebraska counties have been quarantined. Most of those herds are quarantined because they had some contact with the infected herd.

The disease typically spreads from one animal to another through the inhalation of bacteria. Experts say infected animals can transmit the disease to healthy ones within several feet.