Aseptic Meningitis, Riyadh City 1996

There has been an unusual increase in the number of cases of aseptic meningitis (ASM) in Riyadh city recently. Cases of ASM increased 10-fold from a mean of 3.8 cases per month (between June and December 1995) to more than 32 cases per month between January and July 1996. Enteroviruses; including Echoviruses 30, 27, and 33 were isolated from 10 patients. The Field Epidemiology Training Program initiated a study to describe the geographic distribution of the outbreak of ASM in Riyadh City, and to identify risk factors for spread of the disease.

Of 285 cases of meningitis admitted to the five governmental hospitals during the period between June 1995 and July 1996 (Figure 1), the provisional diagnosis for 184 (65%) was ASM (or viral meningitis) and for 45 (15%) it was partially-treated meningitis (PTM). Bacterial meningitis (BM) with a bacterial pathogen or antigen identified in the cerebrospinal fluid (CSF) accounted for 56 (20%) meningitis cases. Cases of BM showed two small peaks during November 1995 and March 1996. Both peaks were due to Hemophilus influenzae type B.

ASM cases were characterized by fever (97%), vomiting (69%), headache (47%), sore throat (40%) and neck rigidity (40%). The average duration of fever was three days. CSF leukocyte count ranged from one to 1950 per nun' (average 160 per mm3) CSF glucose ranged from 2.5 to 4.0 mmo1/1 (average 3.6 mmo1/1). CSF protein ranged from 0.15 to 0.45 gm/I (average 0.39gm/1). The CSF picture for PTM was similar to that of ASM. Physicians prescribed antibiotic treatment for 153 (83%) ASM patients. Antibiotics included ampicillin, penicillin, gentamicin, ceftriaxone, cefotaxime, ceftazidime, and cefuroxime in different combinations. Antibiotics were given for 1 to 15 days (average 8 days).

ASM appeared simultaneously in the southwest and east of Riyadh city (Figure 2). About half of the cases (51.2%) of ASM were in children less than 3 years of age whereas more than half (57.9%) of the cases of BM occurred in children less than one year of age. Fifteen families had more than one person with ASM.

Twenty out of 35 cases (57%) had sewage overflow around their houses compared with 13 controls (19 %) (Odds ratio [OR] = 5.8; 95% confidence interval [95% CI]= 2.2-16 1) Families with cases of ASM evacuate their sewage-holding tank 5.0 times per year whereas control families did this 2.1 times per year (p<0.005, t-test). In the two weeks preceding a child's illness, at least one of the family members suffered from fever; 48% of cases vs. 16% of controls (OR 4.5; 95% CI 1.6-12.8), headache (37% of cases vs. 4% of controls; OR 13.2; 95% CI 3.1-65.8), or vomiting (20% of cases vs. 1% of controls; OR 17.3; 95% CI 1.9-397). Fifteen families with a child with ASM visited a family with a sick child within two weeks preceding their child's illness compared with five control families (OR 9.8; 95% CI 2.8-36).

Echovirus 30 and other enteroviruses produce asymptomatic infections in 50-80% of infected children, or produce a benign, self-limited illness with fever, headache, vomiting, photophobia, and sore throat lasting about 3 days [1]. Convulsions are rarely noted in infants. Antibiotic treatment is ineffective in ASM from enteroviruses, and management is mainly supportive. Hearing tests and C.T. scans are usually not indicated.

Person-to-person transmission probably explains the long duration of the outbreak of ASM in Riyadh City, which continued for more than six months. Cases were more likely to have been exposed to other cases of ASM or to unreported mild cases of enteroviral infections in children that did not need to be taken or admitted to hospitals, of asymptomatic infected persons. Young children often serve as the vehicles for spread within communities. Once infection occurs within a family, susceptible family members are rapidly infected.

Frequent evacuations of sewage-holding tanks among cases and the presence of sewage overflow around houses suggests that polluted peridomiciliary environment contributed to the occurrence of ASM. Fecal shedding of enteroviruses are resistant to chlorine treatment, and have been found to last for 3 to 4 weeks, and occasionally for as long as three months[2].

Other than hand washing and improvement of personal hygiene, there are no effective control measures to halt person-to-person transmission of non-polio enteroviral infections[3]. However alerting doctors on emerging outbreaks of ASM and their causative agents would reduce unnecessary prescription of antibiotics and duration of hospitalization. In absence of appropriate diagnostic facilities, doctors tend to assume that meningitis is of bacterial etiology.