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A newborn died of Lassa fever in the UK, two other family members ill

This transmission electron microscopic (TEM) image depicts Lassa virus virions adjacent to some cell debris.
This transmission electron microscopic (TEM) image depicts Lassa virus virions adjacent to some cell debris. (Image credit: CDC/C.S. Goldsmith)

A newborn baby in the U.K. died last week of Lassa fever — an acute viral illness that is endemic in parts of West Africa. Because the disease doesn't spread easily, however, the chances of a wider outbreak are low, health authorities said.

The infant was one of three confirmed cases of the virus in the U.K.; all of the infected were members of the same family, and they had recently traveled to West Africa, the BBC reported on Feb. 15.

The UK Health Security Agency (UKHSA) reported the death in a statement on Feb. 11, but did not mention the patient's age. One of the sick individuals has already recovered; the other is being treated at the Royal Free London NHS Foundation Trust, according to the UKHSA.

Related:  The deadliest viruses in history

Lassa fever last appeared in the U.K. more than a decade ago, with two cases emerging in 2009. With the recent infections, there have now been 11 cases of Lassa fever in the UK since 1980, UKHSA reported. 

Lassa fever is a zoonotic disease, which means that it is transmitted to people through contact with an infected animal. The animal vector for the virus is a rodent known as the multimammate rat (Mastomys natalensis), which lives throughout West Africa and sheds the virus in its droppings and urine, according to the Centers for Disease Control and Prevention (CDC). People become infected with Lassa through direct exposure to contaminated particles from infected rats, or through contact with an infected person's blood, saliva or excrement.

An estimated 100,000 to 300,000 people are infected by Lassa fever each year, and the disease causes approximately 5,000 deaths, according to the CDC. Symptoms may take up to three weeks to appear after exposure to the virus. In about 80% of cases, signs of illness are nonexistent or mild, and can include headache, minor muscular weakness and low fever. In more severe infections, individuals may experience vomiting, respiratory distress, hemorrhaging, neurological problems and organ failure. However, only about 1% of Lassa fever infections are fatal, the CDC reported.

Officials with the UKHSA are closely monitoring individuals who were in direct contact with the three confirmed cases, including patients and medical workers at the Luton and Dunstable hospital where the infant died, and at Addenbrooke’s hospital in Cambridge, The Guardian reported. No further cases have been identified to date, according to a UKHSA statement released on Feb. 16.

"Cases of Lassa fever are rare in the U.K. and it does not spread easily between people," Dr. Susan Hopkins, Chief Medical Advisor at UKHSA , said in the statement. "The overall risk to the public is very low."

Originally published on Live Science.

Mindy Weisberger
Mindy Weisberger

Mindy Weisberger is a Live Science senior writer covering a general beat that includes climate change, paleontology, weird animal behavior, and space. Mindy holds an M.F.A. in Film from Columbia University; prior to Live Science she produced, wrote and directed media for the American Museum of Natural History in New York City. Her videos about dinosaurs, astrophysics, biodiversity and evolution appear in museums and science centers worldwide, earning awards such as the CINE Golden Eagle and the Communicator Award of Excellence. Her writing has also appeared in Scientific American, The Washington Post and How It Works Magazine.