A disease outbreak is defined as the occurrence of incidences of diseases that appear to be more than what is normally expected in a particular community, geographic area, or season. On the other hand, a cluster refers to the occurrence of incidences of diseases in several people which is more than expected in a specific group, geographical area, or a particular period (Reingold,1998). When reports of diagnosis of disease among several members of a family, neighbors, workers in a particular setting, or community members lead to the same illness, then a disease cluster is suspected.
In determining whether a disease case is a cluster or an outbreak, first, the date of the disease onset should be checked rather than reported (Reingold,1998). In this case, the 12 cases reported could represent 12% or could be 12 cases that were scattered over time but forwarded as a batch. If the 12 cases of tuberculosis and those of West Nile virus that was reported represented recent cases in the county, then both cases would be assumed as clusters. To classify the cases as outbreaks, it will depend on whether the 12 cases surpassed the normal number of cases reported in the county in August. It should be noted that tuberculosis does not have a prominent seasonal distribution (Mobak, 2004). Therefore, the cases reported in August can be compared to either those reported in the preceding months or the cases reported during August of the preceding years. On the other hand, the West Nile virus is a disease that is seasonal and reaches its peak in August through September and October. As such, the number of cases reported in August could be higher than those reported in the preceding months. In determining whether the number of incidences reported in August exceeds the expectations, the number should be compared with those that have been reported in August of the preceding years.
The frequency of the two cases of diseases in the county in five years will provide information that helps make a determination (Reingold, 1998). If the frequency is noted, then it will be easy to determine whether the new cases are extraordinary and cause for alarm or whether the numbers are prevalent in that area. Changes in the reporting procedure, as well as case definitions, help in determining whether the disease cases are outbreaks or clusters. Other important considerations would be the size of the population, referral bias and media awareness. Information may be obtained from the health departments of the state (Selman & Green, 2008). The health departments keep records of reported cases that can help determine whether the reported disease cases are more than the expected numbers as compared to the previous years. The Centers for Disease Control and prevention are a good source of information. In addition, the State health statistics and the communicable disease statistics provide the required information to help determine whether the disease cases are outbreaks of disease clusters.
Outbreaks may occur frequently but not every case is reported. In case this happens, the health agencies must decide whether to handle them in the office or carry out field investigations (Ghosh et al, 2008). The investigation is important because it helps to learn more about the cases to put appropriate prevention and control measures. Every health department responds differently to the reports. The decision on whether to carry out an investigation depends on several grounds, which include factors that are related to the health problem, for example, how severe the disease is, mode of transmission, number of cases and the availability of control and prevention measures (Ghosh et al, 2008). Some health departments are likely to carry out an investigation when the number of reported cases is large.
References
Ghosh, T. S., Patnaik, J. L., Alden, N. B., & Vogt, R. L. (2008). Internet- versus telephone based local outbreak investigations. Emerging Infectious Diseases, 14(6), 975-977.
Mobak, K. (2004). Spread of resistant bacteria and resistance genes from animals to humans—The public health consequences. Journal of Veterinary Medicine Series B, 51(8/9), 364-369.
Reingold, A. L. (1998). Outbreak investigations: A perspective. Emerging Infectious Diseases, 4(1), 21-28.
Selman, C. A., & Green, L. R. (2008). Environmental health specialists’ self-reported foodborne illness outbreak investigation practices. Journal of Environmental Health, 70(6), 16-21.