An Unwelcome Gift from Gorillas

July 3, 2015

By Medical Discovery News


You probably know that Acquired Immunodeficiency Syndrome (AIDS), which has affected 79 million people and killed 39 million since 1981, is the result of Human Immunodeficiency Virus (HIV). What you may not know is that there are several different types of this virus and they did not all come from the same source, making the search for HIV’s origins lengthy and complicated.

There are four groups of HIV-1: M, N, O, and P. Each of them was transmitted between African primates as simian immunodeficiency viruses (SIVs) before infecting humans, and each crossed species to humans independently. More than 40 African primates carry SIVs, which emerged up to 6 million years ago. It is likely that transmission to humans has occurred many times when hunters where exposed to the blood and tissues of infected animals. However the isolation of humans in Africa limited the spread of SIVs that crossed into humans until the last century.

It was not until modern travel allowed infected humans to move from the bush to cities and from there to other cities and countries that an HIV strain such as M took hold among humans, leading to a global pandemic. Group M causes more than 90 percent of AIDS cases and currently affects 40 million people worldwide. We already know that it came from chimpanzees in southern Cameroon. Group N also came from chimpanzees, but has infected less than 20 people.

Group O has infected about 100,000 people in Cameroon, Chad, Gabon, Niger, Nigeria, Senegal, and Togo. Although anti-retroviral drug combinations have made HIV infections survivable, many in Africa and the developing world do not have access to these treatments. Group P has only been isolated from two people. The origins of groups O and P were previously unknown, but now their source has been definitely confirmed: gorillas.

Scientists gathered fecal samples from western lowland, eastern lowland, and mountain gorillas, screening them for SIV antibodies and genetic information. Despite testing many wild troops of gorillas throughout Cameroon, Gabon, the Democratic Republic of Congo, and Uganda, the virus was identified at only four sites. Two strains of SIVs from southwestern Cameroon resembled HIV Group P and one from central Cameroon resembled Group O.

Not only does this data prove that gorillas were the immediate source of groups O and P, but the genetic information revealed that the viruses originated through a cross-species transmission from chimpanzees to gorillas. These are the same chimpanzees that infected humans, leading to groups M and N. Chimpanzees and gorillas share the same habitat, so the virus could have infected a gorilla if it bit a chimpanzee with SIV or was exposed to its blood or tissues.

Understanding the origins of HIV in humans is crucial if we want to prepare for additional viruses, especially SIV variants, entering the human population in the future, which will remain a risk as long as humans continue to hunt and eat primates.

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Why Is Polio Still Around?

Dec. 29, 2012

By Medical Discovery News

An Afghan health worker administers the polio vaccine to a child during a vaccination campaign in 2010 in Kabul, Afghanistan

After plaguing humans for thousands of years, polio is on the verge of being wiped out. In 1988, the virus was endemic in 125 countries, but today it exists in only three: Nigeria, Afghanistan, and Pakistan. With scientists so close to eradicating polio, their work exhibits a renewed sense of urgency.

Polio, also called poliomyelitis or infantile paralysis, is caused by a virus that can infect nerves and lead to partial or complete paralysis. Between the 1840s and 1950s, polio epidemics occurred worldwide, paralyzing or killing half a million people each year.

All that changed in the 1950s with the development of polio vaccines. Over twenty years ago, the World Health Assembly resolved to wipe polio from the Earth by 2000. They got pretty close. During that time, healthcare workers immunized over 2 billion children. 

Since humans are the only reservoirs for polio, there’s an opportunity to eliminate the disease yet that hasn’t happened. Why? Inadequate funding is a major barrier. For example, an 18-month action plan devised by the World Health Organization needs $945 million to be fulfilled.

Logistics and politics are even bigger obstacles. Getting the vaccines to children in remote areas is complicated or made impossible by geopolitics, many of which are anti-U.S. or anti-Western. The Taliban has banned vaccinations in northern Pakistan, an area it controls, to protest American drone strikes. In one of the safe havens inside Pakistan, a local community worker helping with the campaign against polio was shot and killed. Just days before, two gunmen shot a Ghanaian doctor working for the WHO and his Pakistani driver, who were also participating in a polio vaccination campaign. 

Some of the violence is driven by a distrust of humanitarian and healthcare workers. A polio vaccine program in Nigeria eight years ago was undermined by rumors that the vaccine was unsafe and part of a nefarious plan to sterilize Muslim children.  

The CIA exacerbated this distrust by using a fake vaccination campaign to locate Osama Bin Laden. It planned to use DNA obtained through administering a Hepatitis B vaccine to identify Bin Ladin’s children and therefore find the terrorist. The ruse enraged locals, along with critics who blame the CIA for damaging the fragile relationship healthcare workers built with local communities in the anti-polio campaign and other vaccine programs. Furthermore, community workers in these areas became even greater targets of terrorist organizations.

Such complications leave polio-free countries at risk for imported cases. Chad, a country bordering Nigeria, has documented a few cases from people crossing the shared border. An outbreak in China in early 2012 that paralyzed 17 children and killed two is believed to have come from Pakistan.

Already this year, over 100 cases of polio have been reported, although they could have been avoided with a 50-cent vaccine. A valiant effort by multiple nonprofit and governmental agencies is now underway to rid the last vestiges of this disease.

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