Refer to: Ostroy PR: Bacterial meningitis in Washington state (Public Health). West J Med 131:339-343, Oct 1979
Bacterial Meningitis in Washington State PAUL R. OSTROY, MD, Olympia, Washington
During 1977 the state of Washington maintained a surveillance system for reporting cases of bacterial meningitis. Hemophilus influenzae meningitis was the most common etiologic agent causing bacterial meningitis. A high incidence rate for H. influenzae meningitis was found among American Indians less than five years ago. A focus of ampicillin-resistant H. influenzae meningitis was found in Pierce County among military dependents or persons who had family members or relatives working or attending school with Fort Lewis Army Base personnel. Although relationships between the individual cases were not detected, the surveillance system continues to seek some association.
BEGINNING IN JANUARY 1977 the Association of State and Territorial Epidemiologists (ASTE) began surveillance of bacterial meningitis and meningococcemia in 37 states. Information obtained from this surveillance was used for planning the choice and appropriate use of new polysaccharide vaccines that might be effective in preventing the three most common types of meningitis. Additionally, surveillance provided information on the distribution and prevalence of ampicillin-resistant strains of Hemophilus influenzae and meningococcal serotypes. This paper describes the results of the surveillance system maintained by the Epidemiology Section of the Department of Social and Health Services of the state of Washington.
Materials and Methods The Washington State Health Services Division has maintained
reporting system for meningo-
At the time this paper was written the author was EIS Officer, Field Services Division, Bureau of Epidemiology, Center for Disease Control, Atlanta, assigned to the Washington State Department of Social and Health Services, Olympia, Washington. Reprint requests to Major Paul R. Ostroy, MD, MC, US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21701.
coccal (or epidemic) meningitis disease since 1915. The Washington State Reference Laboratory and the King County (Seattle) Laboratory confirm and serogroup all meningococcal isolates. Both laboratories then forward these isolates to the Center for Disease Control for confirmation of identity and serogroup. No other cases of bacterial meningitis have previously been required to be reported to the State Health Services Division. Beginning in early 1977, in cooperation with the Center for Disease Control and ASTE, The Washington State Epidemiology Office sent letters and copies of the bacterial meningitis case report forms to all county health officers soliciting their assistance in reporting all cases of bacterial meningitis. Six months later a similar letter and reporting forms were sent to all nurse epidemiologists and infection control nurses throughout the state of Washington and to the directors of clinical laboratories doing any bacteriologic work within the state. In July 1977 a summary of the results of the first six months of surveillance was reported in the Washington State Communicable Disease Report reinforcing the reporting of bacterial meninTHE WESTERN JOURNAL OF MEDICINE
gitis cases. Finally, letters were sent to the medical records department of selected hospitals requesting that all cases of bacterial meningitis with date of onset in 1977 be reported to the State Health Services Division Epidemiology Section. For the purpose of this study a case of bacterial meningitis was defined as (1) a patient with clinical and laboratory findings consistent with bacterial meningitis who had a positive cerebrospinal fluid cultured for any bacterium and (2) a patient with clinical findings consistent with bacterial meningitis and having a diagnosis of bacterial meningitis made by the primary physician despite a negative cerebrospinal fluid culture. A case of meningococcemia was defined as a patient with clinical findings consistent with meningococcemia and having three or more of the following: purpura, fever, shock, adrenal hemorrhage and positive blood cultures for Neisseria meningitidis. For each case of meningitis and meningococcemia a case report form was completed by a nurse epidemiologist, a county health department nurse or the Epidemic Intelligence Service officer. Data requested included address, age, sex, race, type of illness (bacterial meningitis, meningococcemia or both), the specific bacterium, whether the organism was isolated from blood or cerebrospinal fluid (or both), the date of onset of symptoms and the outcome. For those cases of meningitis caused by H. influenzae, the status of ampicillin-sensitivity was also requested. Before forwarding meningococcal isolates to the Center for Disease Control, the state and King County laboratories carried out antibiotic sensitivity studies to sulfonamides and rifampin using the modification of the Kirby-Bauer disc method on Mueller-Hinton agar." At the Center for Disease Control, final confirmation of identity, sero-
group and antibiotic sensitivities using the minimal inhibitory concentration was completed. The State Reference Laboratory also documented and did antibiotic sensitivities on a small number of other bacterial isolates causing bacterial meningitis. Population data are from the 1977 estimate of the Office of Financial Management of the State of Washington which is based on the 1970 United States census.
Results Of the 203 cases of bacterial meningitis and meningococcemia reported in Washington in 1977, all but four were in Washington residents. Two cases occurred in visitors from California and two from Alaska. The number of cases of meningitis occurring in Washington residents receiving medical care in other states is unknown and, except for meningococcal disease, they would be unlikely to have been reported. Table 1 shows the number of cases, incidence rate, number of deaths and mortality according to etiologic agent for all ages and for children less than five years. Most reported cases were due to H. influenzae (43.3 percent) followed by meningococcal disease (22.2 percent). The overall case-fatality ratio was 13.3 percent. No time clustering was seen for any of the etiologic agents. Of the 203 cases of bacterial meningitis, 161 (79.3 percent) of the reported cases had positive cerebrospinal fluid cultures of a specific bacterium. Although the statewide incidence rate of H. influenzae meningitis for all ages was 2.5 per 100,000, Grays Harbor and Pierce Counties had incidence rates of 6.5 and 5.4, respectively. Of the reported cases of H. influenzae meningitis, 60 percent occurred in residents of the contiguous counties of Snohomish, King and Pierce, which
TABLE 1.-Number of Cases and Deaths, Case-Fatality Ratio (CFR), Incidence and Mortality Due to Bacterial Meningitis Listed by Etiologic Agent in Washington State, 1977 No. Cases
AAU Ages Mortality Incidence No. Rate* Deaths Ratet
Hemophilus influenzae ..... 88 Neisseria meningitidis ...... 45 Streptococcus pneumoniae .. 24 Group B streptococcus ...... 10 Listeria monocytogenes ..... 6 Miscellaneous ............. 30 TOTAL ................ 203
2.5 1.3 0.7 0.3 0.2 0.8 5.8
*Cases per 100,000 population
tDeaths per 100,000 population
OCTOBER 1979 * 131
8 1 10 2 0 6
0.21 0.03 0.27 0.05 0.00 0.16 0.68
Less Than 5 Years No. Mortality Incidence Deaths Ratet Rate*
9.1 2.2 41.7 20.0 0.0 20.0
79 22 11 9 3 10
31.8 8.9 4.4 3.6 1.2 4.0
form the eastern littoral of Puget Sound. Approximately 50 percent of the state's population reside in these counties. Pierce County, which includes Tacoma, reported 2.4 times the number of H. influenzae meningitis cases and 1.8 times the number of meningococcal disease cases expected if the disease was equally distributed among the state's populace. Considering all the causes of bacterial meningitis, the highest incidence rate (54 per 100,000) occurred in children less than five years old and was almost eight times the next highest rate of 7 per 100,000 seen in persons 80 to 84 years old. Table 2 gives the incidence of H. influenzae meningitis, meningococcal disease and all other types of meningitis according to race. American Indians had an H. influenzae meningitis incidence rate of 13.5 per 100,000 which was six times that seen for whites. The difference in the proportion for American Indians and for the rest of the population is highly significant (X2= 15.26; p