Yellow fever is a mosquito born disease that is found throughout South America and sub-Saharan Africa. While the disease is actually more deadly than malaria, it has never been as widely a threat.
In part this is because the first stages are not as severe as malaria’s and it’s usually the secondary effects that lead to mortality. These secondary effects can be quite prolonged. As a result it’s possible that many deaths in sub-Saharan Africa are actually from a yellow fever infection while being diagnosed as something else.
Mostly, however, it’s because persons who recover from the disease acquire virtually complete immunity. This is completely unlike malaria. Persons can succomb to malaria multiple times and likely achieve no immunity against a future infection.
The new research is one of the first in-depth studies that carefully looks at how the disease works. It’s complicated and fascinating. Note that the research was done on macaques, although scientists are fairly confident that the dynamics would be the same in all primates.
The virus switches on and switches off a variety of genes while it resides in the liver.
Over time this leads to a variety of pathological events, including liver and other organ failure.
In the past in Africa mosquito-born diseases like malaria and yellow fever were thought to manifest mortality more quickly and more simply.
As most travelers know there is an effective yellow fever vaccine, although it loses significant effectiveness for very young children and older adults. Persons who obtain the inoculation in their young adult years are easily revaccinated every ten years for extremely good protection.
But the vaccine is expensive and has been difficult to disseminate throughout endemic areas. It is a fragile vaccine that requires refrigeration and is a live-virus based vaccine, which means that incorrect storage or administration can actually give the patient the disease rather than the protection.
By studying the genetic trail of the disease’s manifestations, scientists may be able to interrupt organ damage by neutralizing the proteins that switch certain genes on or off.
Travelers to East Africa are particularly sensitive to not just the pathology but the politics of the disease.
Because vaccination throughout sub-Saharan Africa combined with natural immunity has minimized the disease’s effects over the last half century, many areas of sub-Saharan Africa which have not experienced any yellow fever whatever are particularly susceptible should an outbreak occur.
Tanzania, especially, has reacted to yellow fever outbreaks in neighboring countries like Uganda and The Congo by suddenly – without very much if any notice – requiring incoming visitors to have the inoculation … even though Tanzania itself is yellow fever free.
This has put it from time to time at odds with national health authorities like the CDC that recommend against obtaining the vaccination except for visits to countries that actually have disease outbreaks.
Many other countries in Africa, such as South Africa, require evidence of the vaccination if the traveler has been in an effected country within the last six months.
Genetic science is advancing so quickly that doctors are discovering methods of interruption or curing of diseases that before were thought only capable of being prevented with a vaccine, and that may the route of current science towards the management of this curious and powerful disease.