Study urges consideration of Lassa 'super spreaders'

The Lassa Virus under an electron microscope. | Courtesy of the CDC

A study published in PLOS Neglected Tropical Diseases on Thursday indicated that as many as 20 percent of Lassa fever cases are transmitted through a small group of people.

The study conducted by members of the Dynamic Drivers of Disease in Africa Consortium utilized statistical data in previous outbreaks of the Lassa virus and determined the effective reproduction number, or the amount of secondary infections, from a single infected person. Using the data, researchers surmised which Lassa fever infections were transmitted by humans rather than rodents or other fauna.

Researchers determined that general human-to-human transmission accounted for approximately 20 percent of cases. The study highlighted a specific group of people that have infections of many individuals traced back to them as the source. They deem this small group as "super spreaders" and it is unknown what has caused this disproportion of infection.

"Given the many competing health priorities in West Africa - exacerbated by the current Ebola epidemic - it is essential that we know the relative risk of human-to-human transmission of other potentially deadly diseases, such as Lassa fever," study co-author and University of Cambridge Department of Veterinary Medicine Professor Gianni Lo Iacono said. "That way, public health officials can decide where to focus their public health campaigns and how to prevent or respond to potential outbreaks."

Lassa fever is a viral infection that produces mild symptoms of fever, malaise and headaches in most cases. In 20 percent of cases it can have serious progression of symptoms including hemorrhaging, respiratory distress, and back and chest pain. Occasionally neurological problems arise in the form of hearing loss and tremors. Lassa fever is believed to be transmitted to humans mainly by contact with food or other items exposed to rat urine or feces. There have been some cases of human-to-human transmission.