Lassa Fever Slithers Through Ebola Monitors

By now, most people know of the imported, and ultimately fatal, Lassa Fever case in New Jersey in a traveler from Liberia. This isn't a cause for panic and we've dealt with Lassa importations several times before and though there are many overlapping symptoms between Ebola and Lassa, Lassa is unequivocally more benign.

To me the most fascinating aspect of this case is how this man's travel history was not fully known to treating clinicians in the state in which Kaci Hickox was unjustifiably quarantined during the height of the Ebola hysteria. There's a great New York Times piece on this part of the story. A few important timeline highlights:

  • The man arrived at JFK airport on May 17 from Liberia via Morocco (presumably passing exit screening in Liberia)
  • He deplaned and was not febrile during his entry screen at JFK
  • His case was passed off to local health officials in New Jersey for active monitoring
  • The man developed fever and sore throat prompting a visit to an emergency department where he was treated and released on May 18. 
  • He was unable to be contacted by health department officials on May 18
  • He was reached on May 20 and May 21 and was apparently without fever
  • He represented with worsened symptoms on May 22 and was admitted
  • He died on May 25

There are important implications that arise from the New York Times piece that include:

  • Did the health department in New Jersey know of the patient's visit to the hospital on May 18 at any time prior to his readmission?
  • How are hospitals to know and have situational awareness of who is under active monitoring if the patient doesn't volunteer that information? 
  • All public health response systems require cooperation from the public for optimal function

These events should prompt a re-examing of the current system and emphasize the importance of emphasizing a travel history be taken in all patients with infectious syndromes whether they may have come from Lassa-laden West Africa or Legionnaire's Disease laden Pittsburgh. 

In a more stigmatizing and prejudicial time, bells were unfortunately tied around lepers to warn others of their approach. Such an approach was and is unnecessary for a better alarm bell is simply taking the travel history. 


Ebola: Will it Find the US as Inhospitable as Lassa Fever Did?

While the press is speculating on the ability of the Ebola virus to be imported into the US--a fear heightened by the infection of two Americans--I think it is important to remember that Lassa Fever, Ebola's fellow traveler, has trod this ground before. 

Lassa Fever is a hemorrhagic fever endemic in West Africa and spread via rodent urine and through body fluids. It kills about 5000 people yearly in Africa and, although death is rare, it serves as a prototype of what to do with imported Ebola cases. Bottom line: situational awareness coupled with strict infection control.

Recent Lassa importations occurred in New Jersey in 2004, my home of Pennsylvania in 2010, and Minnesota in 2014. In total, approximately 7 cases of Lassa Fever have been identified in travelers in the US. In all cases, no symptomatic secondary transmission were identified. 

While Ebola is a horrific disease and a serious concern in Africa, should it make itself to the US in a traveler incubating the virus, it will find the US as inhospitable as its weaker fellow gang member, Lassa Fever, has repeatedly learned.

While You Were Thinking About Ebola, Lassa Fever Came Over

While most of the media is occupied with speculating about the likelihood of Ebola utilizing a plane to make an appearance in North America--a feat it has been unable to accomplish--Lassa Fever appeared in Minnesota.

The case involves a traveler to West Africa who presented to a Minnesota hospital on March 31, 2004 with fever and confusion. 

Like Ebola, Lassa Fever is a viral hemorrhagic fever but, in contrast, is spread via rodent urine and has had 8 (counting this episode) appearances in the U.S. related to infected travelers. Another difference from Ebola, which may play a role in its ability to appear in disparate locales, is that its incubation period is at least 1 week. Because of this incubation period length, those harboring Lassa Fever have a higher opportunity to travel whereas those with Ebola have a much lower capacity to do this with an incubation period that can be as short as 2 days (note Ebola can have an incubation period of up to 21 days, so this isn't the total answer). 

What is striking about this Lassa case is that it--again--demonstrates the value of the astute clinician who integrated the patient's symptoms with his travel history and made the diagnosis. 

Chance does favor the prepared mind.