Ebola: Lessons from SARS, the flu, and HIV/AIDS

Ebola: Lessons from SARS, the flu, and HIV/AIDS

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WASHINGTON, October 9, 2014 — The relentless march of the Ebola epidemic through West Africa and the appearance of the disease in Europe and the United States have created a sense of emergency among public health officials, and rapidly growing concern in America that the disease could spread here.

Even if more cases appear in the U.S., the odds that Ebola could become an epidemic are remote: It isn’t easily spread; by the time patients are contagious, they can be quickly and easily identified; and the measures required to isolate it aren’t that difficult — if we are willing to spend the resources to do it. We should be concerned about Ebola, but not afraid.

But the appearance of Ebola, combined with the histories of avian flu, swine flu, SARS and HIV, point to something that is, if not a reason for fear, at least a reason for much more concern than Ebola: zoonoses, or the spread of new infections from animals to humans.

Some of these infections will inevitably be virulent, and some will be much more easily spread than Ebola. SARS (which moved to humans from bats), MERS and swine flu are all examples of diseases that can spread easily and quickly to large numbers of people; virulent forms can have high mortality rates.

AIDS is another zoonotic disease. Like Ebola, AIDS is caused by a virus, HIV. Both are transmitted via bodily fluids; neither has an effective vaccine; and if not treated, both are deadly.

Both diseases originated in Africa, passing to humans from “bush meat” — from handling or consuming the flesh of infected apes and bats. Professor Oliver Pybus of Oxford University’s Department of Zoology is a senior author of a recently released paper from a project lead by the Universities of Oxford, Britain and Leuven, Belgium that reconstructs the history of the HIV pandemic. According to the abstract of their paper, “The early spread and epidemic ignition of HIV-1 in human populations”:

Using statistical approaches applied to HIV-1 sequence data from central Africa, we show that from the 1920s Kinshasa (in what is now the Democratic Republic of Congo) was the focus of early transmission and the source of pre-1960 pandemic viruses elsewhere. Location and dating estimates were validated using the earliest HIV-1 archival sample, also from Kinshasa.

Between the 1920s and 1950s, population growth, increased sexual activity and sexual trade, and ease of transportation bringing people into and out of Kinshasa all contributed to the pandemic. Pybus et al. traced HIV in humans back to 1920s Kinshasa when the virus jumped from a primate to human, most likely as a result of eating or handling bush meat.

What is not known is why the virus that created a pandemic that has killed millions spread outside of Africa when other strains of the virus did not. According to Pybus,

It seems a combination of factors in Kinshasa in the early 20th Century created a ‘perfect storm’ for the emergence of HIV, leading to a generalised epidemic with unstoppable momentum that unrolled across sub-Saharan Africa.

One of the factors the team’s analysis suggests was key to the HIV pandemic’s origins was the increased transportation, in particular its railways, that made Kinshasa one of the best connected of all central African cities.

And allowed the virus to travel outside of Kinshasa.

The paper’s first author, Dr. Nuno Faria of Oxford University’s Department of Zoology says:

Data from colonial archives tells us that by the end of 1940s over one million people were traveling through Kinshasa on the railways each year. Our genetic data tells us that HIV very quickly spread across the Democratic Republic of the Congo (a country the size of Western Europe), traveling with people along railways and waterways …

We think it is likely that the social changes around the independence in 1960 saw the virus ‘break out’ from small groups of infected people to infect the wider population and eventually the world.

The CDC estimated in 2010 that the number of deaths from AIDS in the U.S. at 636,048. Death may be due to variety of reasons — Kaposi’s sarcoma and Pneumocystis pneumonia have been among the most common in the West — but the underlying cause of the death is HIV.

HIV continues to be a leading health issue around the world; more than 34 million people live with the virus. According to the CDC, since the epidemic was first identified, more than 30 million people have died of AIDS or AIDS-related complications.

Microbiologist and physician Peter Piot was 27 when he discovered the Ebola virus. He was working at the Institute of Tropical Medicine, Antwerp when he received the blood of a Flemish nun who had died from what was thought to be yellow fever.

According to a story he wrote for the FT Magazine, from that blood Piot’s lab “isolated a new virus, confirmed by the Centers for Disease Control in Atlanta and subsequently called Ebola, after a river about 100km north of Yambuku, the centre of the epidemic. It turned out to be one of the most deadly viruses known.”

Dr. Piot recalls that the first known outbreak of Ebola was in 1976, when the headmaster of a local school died. At the time of his death he was suffering from high fever, intractable diarrhea and bleeding.

Ebola virus, thought to have jumped to humans from bats, includes four strains, including the deadly “Zaire” that carries a 90 percent mortality rate. Person to person tansmission is through contaminated needles, contact with blood and other body fluids, and contact with the copious vomit and diarrhea produced by those with the full-blown disease.

CDC director Tom Frieden warns that Ebola’s presence in the United States and Europe could foretell of a wider outbreak, predicting the number of cases could mount to 1.4 million by January. “We have to work now so that it is not the world’s next AIDS,” he told the heads of the United Nations, World Bank and International Monetary Fund gathered in Washington.

“I would say that in the 30 years I’ve been working in public health, the only thing like this has been AIDS,” he added, warning of a “long fight” ahead.

Fears are that the disease will reach France before the end of October. Basing predictions on air traffic loads, some experts are predicting the chance for Ebola to migrate to France at 75 percent, and to Britain at 50 percent. Those percentages would drop to 25 and 15 percent if air travel from West Africa were reduced by 80 percent.

The CDC’s Frieden says that the U.S. can and will stop the disease in the United States. “The right steps are being taken, and I am therefore confident we will stop Ebola in its tracks here in the United States.”

The Obama Administration is announcing that screening will begin for all passengers arriving in the U.S. from Ebola infected areas. The screening will begin at five major U.S. airports: JFK and Newark airports in New York, Chicago’s O’Hare Airport, Washington-Dulles in Virginia, and Hartsfield in Atlanta.

It is estimated that this will affect about 150 passengers per day.

The screening will consist of questionnaires and temperature scans. It will not stop anyone with the disease who is asymptomatic and who is not entirely truthful on the questionnaire. It would not have caught Thomas Duncan, who died of Ebola on October 8 in Dallas.

There is widespread doubt about the efficacy of the temperature scans, and the experience of Australia during the SARS outbreak in 2003 is not encouraging. About 1.84 million people were screened for SARS at Australian ports of entry, and 794 were sent into quarantine for further screening. None had SARS. One person who did have it was missed by the screening. The low identification rate in Australia was probably due to screening in other countries before people could board planes to Australia, suggesting that screening that occurs in Sierra Leone, Guinea and Liberia can be much more important and much more effective than screening that will occur at JFK.

The cost of Ebola to West Africa is estimated to reach $750 million over the next six month. The current outbreak has already killed 3,879 people out of the known 8,033 cases according to the World Health Organization (WHO).

The most heavily affected countries are Guinea, Liberia and Sierra Leone all of which are continuing to “deteriorate” according to WHO.

There are other diseases that will spread from animal to human, and the future will bring new pandemics. Cheap and fast travel have made the world even smaller than it was when railroads let HIV spread from Kinshasa. Public health will be crucial when the next pandemic strikes. What we learned from HIV may help us with Ebola, and what we learn from Ebola will be crucial going forward. We are in a biological arms race with nature. It is probably not safe to bet against nature.


EarthSky contributed to this article


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