More PPE protects better against Ebola

We read the article by Dunn et al on Ebola infection among health care staff in Sierra Leone with great interest. Health care staff is at a much greater risk of Ebola infection than the population in general. It is unclear how they can be best protected against these risks. Dunn et al provide valuable information on how well personal protective equipment (PPE) works, but they have not quantified this effect. Even though they present their findings as a case study, they can also be analyzed as a retrospective cohort study of how well various levels of PPE use protect against infection in health care workers.