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Acute conjunctivitis is a common childhood illness; it is probably the most common acute eye disease seen by the practicing physician. Over the past decade, several studies have been published that have significantly increased our understanding of the etiology and epidemiology of this infectious disease. This article summarizes this information so that a physician seeing a child with conjunctivitis will be aware of 1) the potential pathogens, 2) the clinical clues, which suggest a bacterial or viral etiology, and 3) the expected course of acute conjunctivitis in children.
EPIDEMIOLOGY AND MICROBIOLOGY
Both bacteria and viruses are able to cause conjunctivitis. In the pediatric patient, nonepidemic acute conjunctivitis is twice as likely to be due to a bacterial infection than to a viral infection. In our original study of 99 children, ages 1 month to 18 years, 54% of the patients had either Hemophilus influenzae or Streptococcus pneumoniae isolated from their conjunctivae.1 Hemophilus influenzae was never isolated from the eye of any of the 101 age- matched control patients and S pneumoniae was an uncommon isolate (3%), thus supporting the role of these two organisms as causative agents in conjunctivitis. The H influenzae that cause conjunctivitis are usually nontypeable, although type b or other serotypes are occasionally isolated from the eye in this situation. An adenovirus was isolated from 20% of the patients, but again, never from an uninfected control. Based on this statistically significant differential isolation rate, it was possible to implicate one of these three microorganisms as the cause of conjunctivitis in 72% of the patients. Further evidence supporting the fact that H influenzae and adenovirus are etiologic agents in conjunctivitis comes from human volunteer experiments where instillation of either of these organisms into the conjunctival sac resulted in acute conjunctivitis.2'3 Outside of the neonatal period, Chlamydia trachomatis is not a very important cause of conjunctivitis in the United States. It does begin to show up again when adolescents become sexually active, resulting from inoculation of genital secretions into the eye.
The role of Staphylococcus aureus as a cause of conjunctivitis deserves some comment. In the study noted above, the isolation rate of S aureus was no different between patients and controls. Similar findings have been noted in several other studies using control patients....