The Makona strain of Ebola virus (EBOV) circulating in West Africa for the past year takes roughly two days longer to cause terminal disease in an animal model compared to the original 1976 Mayinga strain isolated in Central Africa, according to a new National Institutes of Health (NIH) report. The results provide important information to scientists who have wondered if the EBOV in West Africa is becoming more severe. In fact, the new study suggests the current virus has a decreased ability to cause disease in their animal model compared to the 1976 strain.
Of note, the scientists reported that the immune system of animals in the Makona group produced about three times the amount of a virus-fighting protein, interferon gamma, compared to the Mayinga group. They plan more studies of the immune response, but believe that at least seven days are needed after Ebola infection to mount an effective response. This response does not seem to develop during EBOV-Mayinga infection in cynomolgus macaques because disease progression is too fast.
A Marzi et al. Delayed disease progressi n in cynomolgus macaques infected with Ebola virus Makona strain. Emerging Infectious Diseases DOI: 10.3201/eid2110.150259 (2015).