Meningitis and Cochlear Implants

Source: FDA Public Health Notification, July 24, 2002. (www.accessdata.fda.gov/scripts/medwatch)

Carol A. Kemper, MD, FACP

The FDA issued a public health advisory in late July regarding a possible association between cochlear implants and bacterial meningitis. Cochlear implants are a novel new technology that allows activation of auditory nerve fibers via electrodes implanted in the inner ear. An estimated 60,000 individuals worldwide have been implanted with the devices. Unfortunately, at least 25 adults and children with the implants, varying in age from 21 months to 63 years, have developed meningitis. Nine persons have died. Infections in several patients were due to pneumococcus (none of these persons were vaccinated to this organism). The basis for the increased risk of infection is not clear, but probably is not a result of contamination of the device. Rather, it is believed that many people who are candidates for the device have sub-chronic or chronic otitis, or congenital abnormalities that predispose them to middle ear infections—and subsequent meningitis. The device may additionally serve as a nidus of infection in the inner ear.

The FDA is seeking information regarding possible additional cases (Office of Surveillance and Biometrics, e-mail: phann@cdrh.fda.gov). In the meantime, it has been suggested that patients receiving cochlear implants receive prophylactic antibiotics or treatment for middle ear infection prior to surgery. The immunization status of candidates should be evaluated and consideration should be given to vaccination against S pneumoniae and Hemophilus influenzae.

Monkeypox Genome: A Surprise Inside

Source: Shchelkunov SN, et al. Virology. 2002;297:172-194.

Shchelkunov and colleagues successfully sequenced and analyzed the 196,858 base-pair genome of the monkeypox virus and compared its key gene structures to human smallpox. While certain innate elements of the orthopoxvirus genome were identified in the monkeypox gene structure, significant differences were found between the host range genes and the immunomodulatory genes for human and monkey pox viruses. Shchelkunov et al have therefore concluded that monkeypox is probably not related to smallpox and instead represents a distinct species of pox virus—blowing out theories that smallpox was some kind of ancestral derivative of monkeypox.

Monkeypox is endemic in Africa and occasionally results in a pustular disease in humans reminiscent of human smallpox, although person to person transmission is unusual. Concerns have been raised that possible bioengineering of the monkeypox genome could result in the successfully creation of a new and improved pox virus, or that the monkeypox could "jump" species, resulting in an outbreak of human disease. This study suggests otherwise. 

"Polioman" Discovered in Europe

Source: Pro-MED-mail post, July 23, 2002; www.promedmail.org.

Pursuant to Dr. Deresinski’s recent summary of an outbreak of poliovirus infection due to a mutant strain of vaccine-derived OPV-1 found circulating in the Dominican Republic and Haiti, proMED-mail picked up this report from the BBC regarding the discovery of a young, immune deficient man who has chronically excreted poliovirus for years. The man was first discovered in 1995, when he presented with chronic diarrhea. Subsequent evaluation of his stools revealed the presence of poliovirus. The man had been vaccinated against polio and has remarkably not developed systemic or neurologic signs of infection, despite his immunosuppressed condition. Health experts suggest his virus may have naturally attenuated to a less virulent form, although his prior vaccination may have provided some protection against infection.

Immunodeficient hosts have been known to excrete vaccine-derived virus in stools for months to years; for example, one immuno-incompetent individual has reportedly excreted vaccine-derived virus for 16 years. However, the recognition of "polioman," who excretes wild type virus, and the concern that other cases like him may exist elsewhere, has led many experts to pause and rethink how to go about terminating existing vaccine programs in the Western world.

Dr. Kemper, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center, is Associate Editor of Infectious Disease Alert.