Airborne transmission of Ebola virus -- which has never been documented in humans -- apparently occurred between monkeys that were caged three meters apart in a research lab, the authors report.
Secondary transmission of Ebola virus infection in humans is known to be caused by direct contact with infected patients or body fluids, but airborne transmission has been a theoretical concern. The findings underscore the need for "eye and oronasal mask protection" as infection control precautions for personnel exposed to the virus, the authors recommend.
They report transmission of the virus to two of three rhesus monkeys that did not have direct contact with experimentally inoculated monkeys held in the same room. The two control monkeys died from Ebola virus infections at 10 and 11 days after the last inoculated monkey had died. During the course of the experiment, blood and viral swab sampling procedures were always performed first on control animals, and individual needles and swabs were used for every procedure. That practice presumably eliminated the possibility of inadvertent needle or swab transmission of the virus as a possible mode of infection. Fomite or contact droplet transmission of the virus between cages also was considered unlikely.
"Standard procedures in our BL4 containment laboratories have always been successful in the prevention of transmission of Ebola or Marburg virus to uninfected animals," the authors note. "Thus, pulmonary, nasopharyngeal, oral, or conjunctival exposure to airborne droplets of the virus had to be considered as the most likely mode of infection."
Ebola virus replicates extensively in infected nonhuman primates, reaching high concentrations in tissues, they add, suggesting that although viral titers in body secretions and excretions are lower than in blood, they are apparently high enough to transmit infection.
"This idea is supported by our report, and by previously determined experimental aerosol infective doses," they conclude. "While airborne transmission of Ebola hemorrhagic fever has not been documented in humans, only limited tissues have been available for complete virological and histopathological examinations. . . . These data also suggest potential avenues of exploration regarding the routes of infection for index human cases of Ebola fever, which remain a mystery."
Telzak EE, Sepkowitz K, Alpert P, et al. Multidrug-resistant tuberculosis in patients without HIV infection. N Engl J Med 1995; 333:907-911.
HIV-negative patients with multidrug-resistant tuberculosis, contrary to previous reports, can respond well to chemotherapy -- both clinically and microbiologically, the authors found.
Investigations of outbreaks of multidrug-resistant TB have found low rates of treatment response and very high mortality, but they have mainly involved patients with advanced HIV infection. For patients without HIV infection, anther study found mixed response to treatment and mortality of 22%, they note. However, they found that 24 of 25 HIV-negative TB patients had clinical response to treatment.
"We have shown that HIV-negative patients with multidrug-resistant TB can be expected to have a good response to medical therapy," they conclude. "All of our patients who received appropriate therapy have had clinical and microbiologic responses. There were no relapses or treatment failures during a median follow-up period of 91 weeks. It is still possible that some of these patients will relapse."
Spitalnic SJ, Woolard RH, Mermel LA. The significance of changing needles when inoculating blood cultures: A meta-analysis. Clin Infect Dis 1995; 21:1,103-1,106.
A meta-analysis demonstrated reduced blood culture contamination when needles used for phlebotomy are changed prior to inoculation, and the findings should be considered when setting clinical policy, the authors recommend.
They found a statistically significant decrease in the rate of blood culture contamination if inoculation was done after a needle change.
"When developing protocols for the performance of blood cultures, practitioners must weigh the decreased likelihood of blood culture contamination with a needle change against the risk of needlestick injuries," they report. "Minimizing contamination by optimizing other aspects of blood culture specimen collection -- e.g., careful attention to cutaneous antisepsis and proper phlebotomist training -- may reduce the added benefit of a needle change. Using a separate needle to inoculate blood culture bottles after venipuncture should be considered when effective devices are available that eliminate the risk of needlestick injury."
Several recent studies have concluded that the changing of needles prior to inoculation of blood culture bottles does not reduce the contamination rate, although there is a consistent trend toward a reduction in number of contaminated cultures when the needle is changed prior to inoculation, the authors note. They performed a meta-analysis of available studies prospectively comparing blood culture contamination rates with and without a needle change prior to inoculation. The overall weighted contamination rate when the needle was changed prior to inoculation was 2%, compared to 3.7% when the needle was not changed. Since an increase of some $5,000 in costs per patient is associated with a contaminated blood culture, the reduction in contamination rate could save an estimated $85,000 for every 1,000 cultures performed, they conclude. *