Ebola Mutating

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Is Ebola mutating?

Yes. The question really is: Does it matter?

Viruses mutate.

Influenza mutates. Mumps mutates. Polio mutates. The sun rises. The sun sets.

RNA viruses – like Ebola – mutate even faster than other viruses. When RNA viruses copy themselves, they don’t proofread as well as DNA viruses. There are always a lot of mutations.

Some viruses change rapidly. Influenza –plentiful worldwide - mixes and matches between strains.

Other viruses change less, like measles.

Ebola mutates

Ebola is succinct. It doesn’t have much genetic information. It is a single stranded (and negative sense) RNA virus that is 19,000 nucleotides long. This isn’t a lot. Humans have 3 billion pairs. But viruses tend to be very small, tightly packing in a lot of havoc. Ebola brings badness through just 7 proteins.

Scientists have looked back at the spread of the Ebola virus in West Africa. They saw a lot of genetic mutation – within patients and between patients. The virus had been mutating as it was copied again and again. Ebola can reach as high as a million copies per milliliter of blood in people who survive – and much higher in those who do not. Multiply that by the thousands of people who have become infected. That’s a lot of copying – and a lot of chances of bad proofreading creating mutations.

Despite all of these mutations, the scientists could see that these strains pointed back to just one introduction – thought to be from a bat.

Ebola was mutating but that didn't mean it would be more dangerous.

Mutations don’t always matter

Mutations don’t mean a virus is becoming more contagious or more vicious. Making a copy of a virus is a bit like playing a piece on the piano. A mutation is like hitting a wrong note when playing music. Usually a wrong note makes the piece worse.

It may not affect it much. It might ruin the piece entirely. Only rarely does it make a piece more popular. Only rarely will a mutation make a disease spread more.

The mutations found haven’t been shown to have a biological importance. As Dr Gire of Harvard University who has worked on these genetic sequences has pointed out, worrying about whether Ebola will mutate and become airborne would be like worrying about rats mutating and growing wings. Those who are immune appear to remain immune even as the virus continues to change slightly. There hasn’t been concern that vaccines being developed would need to keep up with a rapidly changing virus - and in fact strains from prior, related outbreaks are looked at in vaccine development.

Dr Anthony Fauci, the National Institute for Allergy and Infectious Diseases Director, has said: "It isn't surprising at all that the virus is mutating". He adds, there has been little worry about the virus changing biologically.

Ebola was probably there before we knew it.

Before we knew Ebola was in West Africa, it was probably there. Scientists looked back at blood stored from patients who had come to the hospital who were thought to – but tested negative for – Lassa fever. This disease is a viral hemorrhagic fever found in West Africa where Ebola is spreading. Lassa can resemble Ebola but fewer die from a case of it (about 10%) - but there are more cases of Lassa, usually. This means that usually substantially more people die from Lassa (5000) a year in West Africa than from Ebola, which has taken over 11,000 lives since 2013, but which up until 2013 had resulted in almost no known cases in West Africa.  Many of the patients thought to have Lassa who tested negative for Lassa Fever died (36%). What is interesting is that from 2011-4, among those thought to have Lassa but Lassa negative, patients 22% tested positive for Ebola antibodies. (However, only 1 at most was seen to have possibly virus in the blood sample, which would have indicated a current infection). Some of these patients may have been sick with Ebola; some may have had prior infections.

Ebola has probably jumped from animal to human many times over the years in West Africa.

If there was Ebola in the area before, these cases of past Ebola likely came from animals.

We know in nearby Cote d’Ivoire, there has been one case of Ebola, of a different strain (Taï Forest ebolavirus), that came from chimpanzees, who also died from Ebola. These antibodies show that it is likely that people have been infected before.

Why is it spreading now?

For the disease to spread, there needs to be the right mix – and maybe the wrong luck. It doesn't mean that the infection has mutated to be more contagious. Many factors can affect when a disease spread. Dry weather and animal (ie bat) migrations can affect whether humans come in contact with animals carrying Ebola. Road improvements may help – both spread a disease faster and wide and allow for response to the disease. Those who are silently incubating a disease may travel farther; those who are sick may seek care or return to see family with better roads. In addition, many cases could initially be traced back to a large funeral of a very popular traditional healer who died after trying to cure patients, which resulted in sudden spread of the disease in some areas. There are many factors that have led Ebola to spread in West Africa.

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