Spatial distribution and temporal trend of Influenza in Veteran population

Influenza (flu) is an infectious respiratory disease. Symptoms of the patients can vary from mild illness to death. Every year in the United States, on average more than 200,000 people are hospitalized and about 36,000 people die from flu. Objective: To explore early event detection for the influenza, we need to monitor the extent of disease through space and time. Method: Data from veteran electronic patient records for influenza hospitalization in Baltimore, Maryland was used. Incidence rate of influenza hospitalization based on new cases per1000 veterans from 1999-2005 was calculated and mapped using the patient's zip code. These data were analyzed using GIS and statistical techniques. Results: The temporal pattern of incidence shows that the rate continuously increased from 1999-2005. Means of incidence rate are in the range of 0.23 to 0.54 new cases per1000 veterans. The higher rate is found in the winter, especially in January and the lower rate is found in the mid year with the lowest in July. For the incidence rate of the disease by geography, we find that among 30 compared zip codes; difference between the means is significant, with a range of 0.12-0.51 cases per 1000 veterans. Geocoding indicates that 3 adjacent zip codes that have the highest rates are 21223, 21216 and 21217 whereas the lowest rate is 21201. CONCLUSION: The incidences of influenza vary by space and time. The results may be used by the state or other entities to make public policy decisions regarding early event detection for this disease.