The purpose of surveillance is to try to detect where disease organisms, such as bacteria and viruses, might be located in Texas in order to predict and prevent human illness. Two main types of surveillance activities are conducted.
Most disease surveillance in Texas is passive surveillance. This process relies on confirmed case reports from physicians, veterinarians, laboratories, and others. The Texas Veterinary Medical Diagnostic Laboratory is one of the key sources of surveillance information for animal disease.
Active surveillance is a process whereby state or local agencies actually look for evidence of disease risk. For example, when trying to find if a certain virus carried by mosquitoes is in Texas, mosquitoes are collected and sent to the lab for testing. If a mosquito is positive, it means that the virus was found during testing. If a mosquito is negative, it means that the virus was not found during testing. Similar surveillance is conducted on other insects and samples from animals for a variety of diseases.
The amount of testing in the surveillance process will vary for different counties statewide. If a report indicates that an area does not have any positive test results for a particular disease, it does not necessarily mean that the disease organisms are not in that area. It just reflects that no positive tests on collected insects or other samples have been reported from that area.