Researchers suggest some emerging infectious diseases may have been around a long time

November 9, 2012 by Bob Yirka report
Electron micrograph of an Ebola virus virion. Credit: CDC/Cynthia Goldsmith

(Medical Xpress)—A genetics research team led by Pardis Sabeti of Harvard University has published a paper in the journal Science, suggesting that some infectious diseases that are thought to be relatively new, may in fact have been around for thousands of years. They claim they have genetic evidence that shows that some diseases such as Ebola and Lassa, which some believe first began infecting people in just the past half century, likely have been around for hundreds and in some cases thousands of years.

Recent field evidence has suggested that some people that live in areas where such diseases are common show rates of exposure to Ebola and Lassa that are high enough to indicate that some have developed an immunity to them. Last year, for example, blood tests showed that up to 55 percent of the population in a community in Guinea had been exposed to Lassa and 22 percent had been exposed to Ebola. Generally it takes many generations to build up such a level of immunity.

Additionally, in studying the genetic structure of Ebola and Lassa, the researchers found that Lassa appears to have diverged from a family of hemorrhagic diseases approximately 500 hundred years ago. Ebola appears to go back even further, having diverged from the approximately 10,000 years ago.

In studying field reports regarding Ebola and Lassa the researchers also found that both can show symptoms that differ from those that have been commonly associated with them, namely mucosal and internal bleeding. Sometimes, they found, victims with the diseases show no signs of bleeding – instead they have a fever, cough or sore throat. In such situations, it's likely others believed they had contracted another disease. Such cases they say, might explain why so many researchers have come to conclude that both are among those classified as . Instead they suggest, it's more of an emerging diagnosis trend.

The team suggests that if Lassa and are diseases that are newly diagnosed, rather than emerging, it makes sense that others likely are as well. And if that is the case, then research that focuses on which populations are harboring them might turn up data to better predict when an outbreak might occur.

Explore further: Lassa fever kills 40 in Nigeria: official

More information: Emerging Disease or Diagnosis? Science, 9 November 2012: Vol. 338 no. 6108 pp. 750-752 DOI: 10.1126/science.1225893

Outbreaks this year of the deadly and highly contagious Ebola and Marburg viruses in the Democratic Republic of Congo and Uganda and Lassa virus in Nigeria raised concerns about possible epidemic spread of these hemorrhagic fevers. These pathogens seemed to appear out of nowhere around the middle of the 20th century: Marburg virus in 1967, Lassa virus in 1969, and Ebola virus in 1976. By the early 1990s, public health concerns were crystallized in a landmark report (1) that was the first to popularize the concept of "emerging pathogens". But could "emerging diagnosis" explain the rise in appearance of hemorrhagic fevers caused by these pathogens? Recent epidemiologic and genetic studies of Lassa and Ebola fevers suggest that these diseases may have widespread prevalence and ancient origins. They raise the possibility that some viral infections may reflect "emerging diagnoses" of diseases that are circulating more widely than thought, with an emerging character primarily a matter of improved detection of the culprit pathogens.

Related Stories

Lassa fever kills 40 in Nigeria: official

February 22, 2012

An outbreak of Lassa fever has killed 40 people and infected dozens of others in a third of Nigeria's 36 states over the past six weeks, a senior health official said Wednesday.

Officials: Ebola breaks out in Uganda

July 28, 2012

(AP) — The deadly Ebola virus has killed 14 people in western Uganda this month, Ugandan health officials said on Saturday, ending weeks of speculation about the cause of a strange disease that had many people fleeing ...

WHO official: Ebola under control in Uganda

August 3, 2012

(AP) — Doctors were slow to respond to an outbreak of Ebola in Uganda because symptoms weren't always typical, but a World Health Organization official said Friday that authorities are halting the spread of the deadly ...

Uganda Ebola outbreak 'coming to an end': WHO

September 3, 2012

Uganda's latest outbreak of the deadly Ebola virus appears to be over, the World Health Organisation said Monday, pointing out that no new cases had been confirmed for the past month.

Recommended for you

Monkeys in Asia harbor virus from humans, other species

November 19, 2015

When it comes to spreading viruses, bats are thought to be among the worst. Now a new study of nearly 900 nonhuman primates in Bangladesh and Cambodia shows that macaques harbor more diverse astroviruses, which can cause ...

One-step test for hepatitis C virus infection developed

November 14, 2015

UC Irvine Health researchers have developed a cost-effective one-step test that screens, detects and confirms hepatitis C virus (HCV) infections. Dr. Ke-Qin Hu, director of hepatology services, will present findings at the ...

Computer model reveals deadly route of Ebola outbreak

November 10, 2015

Using a novel statistical model, a research team led by Columbia University's Mailman School of Public Health mapped the spread of the 2014-2015 Ebola outbreak in Sierra Leone, providing the most detailed picture to date ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.