As of August 19, the 2240 suspected or confirmed cases of Ebola Virus Disease (EVD) in West Africa have resulted in 1229 deaths; though it's feared that the numbers are underreported. The outbreak continues to grow and treatment options are somewhat limited, as there really aren’t any effective approved antivirals. The World Health Organization (WHO) is considering unconventional techniques in order to curb the spread, including last week’s approval of the use of unapproved experimental treatments. WHO is now debating whether or not to begin administering blood from those who have survived the disease into the sick, in an effort to pass antibodies along.
When a pathogen enters the body, the immune system is able to recognize it is foreign because of proteins on the pathogen’s surface (called the antigen). The immune system is then able to create antibodies that can eliminate the threat, and is also able to remember the antigen in case it comes up again. If someone currently ill was given a blood transfusion from someone who had overcome the disease, that could give them the antibodies needed to better fight the infection. This method is known as a convalescent serum and while it has been an effective technique in other illnesses, there isn’t a lot of hard evidence that it works with the Ebola virus.
Studies involving the use of convalescent serum are fairly limited. There was an outbreak of EVD in what is now the Democratic Republic of the Congo in 1995; then known as Zaire. The outbreak was caused by the same strain of Ebola that is currently causing disease, though the mortality rate was 80%, compared the 55% of the current outbreak. A convalescent serum was administered to eight individuals from five sources, and seven of those patients survived. That seems to be a fairly convincing argument that the serum should be used, right? Well, not so fast.
The seven patients who received the serum and survived were all given the treatment 7-15 days after the onset of symptoms, and were likely going to survive the illness anyway. The patient that died was given the serum 4 days after becoming symptomatic, so that study didn’t yield any evidence that the serum actually did anything.
Of course, that was a very small trial and many other factors could have played a role in the outcome. However, studies using animal models that were better controlled have not been able to produce results that were any more promising.
American doctor Kent Brantly received convalescent serum from a 14-year-old patient he had treated earlier in the summer before falling ill himself. Brantly and his associate Nancy Writebol also received an experimental serum known as ZMapp, which was based off of three different antibodies from animal sources. Though Brantly issued a statement last week saying he was regaining strength, it is unknown what role, if any, the serums played in his recovery.
However, if WHO does approve the use of this technique, it is something that could be widely implemented relatively easily. While experimental serums are produced in small quantities on a different continent, doctors in West Africa have immediate access to the EVD survivors for blood donors. While the blood would need to be screened for other infectious disease like HIV, it could be an option worth exploring in some areas.
[Hat tip: Kai Kupferschmidt, Science]
NOTE: An earlier version of this article read "...blood would need to be screened for other infectious disease like HIV/AIDS..." HIV is a transmissible virus, but AIDS is a condition caused by HIV. The article has been edited to correct and clarify the point that AIDS itself is not an infectious disease.