Last week, the UK declared its first brush for more than a decade with a rare tropical disease, similar in some ways to Ebola, called Lassa Fever. An individual returned with the infection following a trip abroad and subsequently transmitted it to another family member. This also led to the infection of their newborn baby, which tragically died. Because the diagnosis was only confirmed later, there were many healthcare workers, at two hospitals, who had cared for the victims when they first became ill but may not have used the level of personal protective equipment required to defend against infections of this sort. As a result, a massive contact tracing effort has been launched to ensure that those staff members remain safe and to prevent any further onward transmission of the infection. The downside of doing this is that other healthcare activities have had to be limited owing to staff isolating. To tell us more about Lassa Fever and the history of its discovery, study, origins and impacts on our health, here are Julia Ravey and Harry Lewis…
Julia - Lassa Fever gets its name from the town in Nigeria, where the first cases were officially documented in January, 1969. A nurse Laura Wine, working in the Lassa Mission Hospital fell ill shortly after looking after a pregnant patient with what appeared to be the same disease. Both had a high fever and flu-like symptoms, severe fatigue, pains in the chest and muscles, and more alarmingly, bleeding from their gums. Sites where blood samples were drawn, continued to bleed afterwards.
Harry - Despite being airlifted to a bigger hospital, Laura Wine died the next day. Shortly after two other nurses who had been caring for her themselves became ill. And one of them also died. The other, Lilly Pinneo was flown to New York where she subsequently recovered in an isolation unit. The pattern of spread and the timing with which the cases developed symptoms suggests to the medical team that hitherto unknown virus might be behind the cases.
Julia - They sent the samples from Lily Pinneo and the other victims in Nigeria to a number of labs, including a specialist team at Yale University. Headed by Spanish doctor, Jordi Casals, who would set up a unit there to study, identify and classify exotic diseases.
Harry - Regrettably, and perhaps as a reminder of the power of the genie that they were trying to coax from its bottle, within three months, the virus nearly claimed its next victim. Casals' health developed the infection. Complaining of severe cold light symptoms and a running fever. He was placed into isolation and tests confirmed that he was positive for the very virus he was trying to study.
Julia - In an ironic twist of fate, having been the source of the virus that could kill him, the now convalescing Lily Pinneo then came to the rescue by allowing doctors to transfuse him with antibodies collected from her blood.
Harry - The intervention appeared to work. Once he recovered, together with colleague Sonya Buckley, Casals was able to resume work on the virus leading, within a year, to its successful isolation and identification, which they published together in the journal Nature. His own brush with Lassa Fever meant that Casals was in no doubt about the infectious and dangerous nature of this agent. His other major contribution was to lay the foundations of many of the biosafety protocols used today to safeguard against laboratory and hospital spread of infectious diseases.
Julia - Relying on these techniques, scientists have since been able to learn a lot more about Lassa Fever in the subsequent 50 years. We now know it's naturally carried by mouse species native to a number of countries in West Africa. Once the mouse picks up the virus, it becomes a lifelong carrier, shedding the infection in urine and faeces.
Harry - Humans exposed to this material, for instance when cleaning or sweeping, can inhale the infectious debris which can also make its way into cuts or other breaches in the skin. The symptoms usually take from a few days to a few weeks to kick in. Usually, a fever is the most characteristic feature.
Julia - A flu-like illness is common and because the virus attacks the linings of blood vessels, blood clotting can be affected, which is why some developed bleeding from their gums, back passage, and even sometimes their eyes.
Harry - Like many infections though, Lassa is more severe in pregnancy and often transmits to the developing baby; Usually lethally.
Julia - Surprisingly though, over 80% of the half a million cases that occur in endemic areas of West Africa each year are asymptomatic. About a fifth of cases are more severe, and about 5% of cases end up in hospital. The mortality rate is about 1 person in every 100.
Harry - The virus is present in blood and other body fluids, including urine, for several weeks. Men can continue to shed the Lassa virus in seminal fluid for several months after they recover, meaning that sexual transmission of this infection is well documented. People caring for Lassa Fever for patients, therefore need to take steps to avoid exposure to any of these body fluids.
Julia - We can test for Lassa Fever using PCR to detect the genetic material of the virus. Or we can look for antibodies to the virus in the blood. But there are no treatments for Lassa infection other than supportive therapy to keep patients hydrated and stable while they recover.
Harry - The antiviral drug ribavirin is sometimes used, but the evidence for its effects are quite weak. At the moment, there is no vaccine for Lassa, although experimental agents were developed in the past and appear to be effective. Perhaps, some are saying, the very useful RNA technology developed to help combat COVID 19 can be brought to bear against Lassa too, in the future.
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