What Is Lassa Fever?
“Lassa fever” is known as Lassa hemorrhagic fever (LHF). It is a type of viral hemorrhagic fever caused by a virus: the Lassa virus. It is a disease that spread by rats, an animal born and zoonotic disease manifested by an acute viral illness. It mainly affects people in parts of West Africa, where about 300,000 cases of Lassa fever were diagnosed and about 5,000 deaths are recorded yearly. One reports number of cases a year at 3 million.
Description of the disease date from the 1950’s but the first case was described in 1969 in the Nigerian town of Lassa following the death of two missionary nurses. Symptoms described with Lassa fever are fever, weakness, headaches, vomiting and muscle pain. Less commonly, there may be signs of bleeding from the mouth or the gastrointestinal tract. Individuals may also show signs of respiratory breathing difficulties with possible life-threatening conditions. The infection affects females 1.2 times more than males and the predominant age to be infected is between 20 and 30 years.
A rodent (multimammate rat or Mastomy’s natalensis) carries the Lassa virus in his feces and its urine. These rats are found mainly in West Africa (Sierra Leone, Guinea, Nigeria, Liberia) and Central Africa (Mali. Senegal, Ghana) and also in East Africa. They live in home and in places where food is stored. The Lassa virus is considered as a single stranded RNA virus belonging to the Arenaviridae family and has been classified as a category A bioterrorism agent.
The infected rat comes into contact with the humans via the dropping or the pee or others will catch the disease while they are eating those rodents or inhale tiny airborne infected particles found in the rat’s poop. It is admitted that at least 15% of people admitted in hospitals in the above areas, have Lassa fever. One can understand the impact of such disease on the population.
Lassa disease can be rarely transmitted from person to person especially whenever a person become sick with the disease. The transmission can happen through the blood or the body fluid and by direct contact through the eyes, the nose or the mouth. The disease can also be transmitted through casual contact like holding hands, hugging or any other closed contacts like even sitting close by. Generally contact with the urine or the feces in an infected mouse will spread the disease.
In the prodromal phase, the individual with the virus, becomes contagious. Lassa virus is easily transmitted through re-used needles or any other contaminated medical equipment. Lassa fever has been found also in dogs, cats and horses.
The onset of the symptoms is seen between seven (7) to twenty-one (21) days after exposure to the Lassa virus. The majority of people (80%) will remain asymptomatic while others (20%) will present with symptoms like fever tiredness, weakness, headaches and as already revealed above, a few may develop more serious complications like bleeding gums, chest pain and breathing problems. Others will present with low blood pressure, hearing loss improving with time. They may also develop vomiting, chest and belly pain and even can fall into a septic shock.
Any pregnant woman can be at risk for developing a miscarriage once they become infected with the Lassa virus. One (1/3) third of the cases may also develop deafness but only 1% may die from the disease. The death rate increases to 30% for women in their late stages of pregnancy. More death is seen with multiple organ failure within 2 weeks of the start of the symptoms. Miscarriage nay occur in 95% of child bearing women and at this stage, Lassa fever may be difficult to distinguish clinically from other viral hemorrhagic fevers… such as Ebola.
At this point, many suffering from Lassa Fever, will present with pharyngitis and excessive proteinuria and Fever as a hallmark. Death may occur in e weeks following the beginning of the symptoms. About 1% of the Lassa fever infections will die but 20% of the patient who require hospitalization for Lassa fever may die with an even higher risk for the pregnant women. A “swollen baby syndrome” is also described in the newborns, infants or toddlers seen with pitting edema and abdominal distention as well as bleeding.
The diagnosis may be difficult, based on symptoms. The confirmation can be done through laboratory testing to detect the virus’s RNA antibodies or the virus itself via cell culture. Other conditions may present similarly like Ebola, Malaria, Typhoid Fever and even Yellow Fever. The Lassa virus is a member of the “Arenaviridae” family of virus.
In the United States, it is unlikely that someone will catch the disease. Only six (6) cases of Lassa fever were reported in 2015 and all cases were linked to people who become in contact with the virus while returning to a trip from Africa. Countries like Sierra Leone, Liberia, Guinea and Nigeria were found to have the higher incidence for the disease.
In England three cases were recently discovered and all were linked to traveling to West Africa. All three of them were treated at a Bedfordshire Hospital. One of the patients has recovered. Since 1980, there has been 8 known cases.
With a prodromal phase (incubation period) extending from one to three weeks, most people who catches the virus may present mild symptoms of fever, tiredness and headache. 20% of the infected persons will develop more serious complications and start experiencing bleeding in the gums, the eyes or the nose. Others may present with hearing loss which improve in time. They may also develop trouble with breathing, vomiting, chest and belly pain and even can fall into a septic shock.
Any pregnant woman can be at risk for developing a miscarriage once they become infected with the Lassa virus. One (1/3) third of the cases may also develop deafness but only 1% may die from the disease. The death rate increases to 30% for women in their late stages of pregnancy. More death with multiple organ failure can happen within 2 weeks of the start of the symptoms.
The diagnosis may be difficult, based on symptoms. The confirmation can be done through laboratory testing to detect the virus’s RNA antibodies or the virus itself via cell culture. At early stages of the disease, a nose or throat swab could help make the diagnosis. Other conditions may present similarly like Ebola, Malaria, Typhoid Fever and even Yellow Fever. The Lassa virus is a member of the “Arenaviridae” family of virus.
There is no vaccine for the disease and the best treatment may be obtained with prevention. To prevent, it is necessary to isolate the infected cases while also decreasing contact with the mice. In places, having a cat at home to hunt the mice and the use of sealed containers for the food, remain the best methods of prevention. Prevention when you are travelling to West Africa is the best way to avoid contracting the disease. Stay away from the rats. Store your food in rat-proof containers, keep your quarter clean and avoid cooking or eating rats. Researchers are working on a vaccine which hopefully will bring hope in controlling this disease.
Treatment is mainly through an antiviral medication called “Ribavirin” which has been recommended to be given as soon as the symptoms of the disease are discovered. Orally or parenterally are generally the most common routes used for dispensing the treatment. Evidence to support such treatment remains weak and has worsened outcomes in certain cases. Intravenous interferon therapy has been also used. Often an admission to a healthcare facility or a hospital is necessary to facilitate hydration, oxygenation and monitoring of the blood pressure. Fluid replacement, blood transfusions and medication for low blood pressure may be needed,
During a third trimester pregnancy, when Larissa Fever is diagnosed in a pregnant woman, inducing the delivery is recommended for the mother to have the best chance of survival. The virus has an affinity to the placenta and other vascular tissues. The chances for the fetus to survive is 1/10 no matter what course of action is taken. In this case, saving the life of the mother is primordial. After delivery, the women will receive the above treatment as described for Lassa fever. In all pregnant women, abortion will decrease their death rate but some women may experience lasting effect of the disease like by example a partial or permanent deafness.
This is mainly what we would like to teach on how to prevent and treat the Lassa disease to anybody adventuring self in the countries of West, Central and Eastern Africa.
Maxime Coles MD
Boca Raton FL
1- Ogbu O, Ajuluchukwu E, Uneke CJ (2007). “Lassa Fever in West African sub-region: an overview”. Journal of Vector Borne Diseases; 44 (1): 1-11.
2- Yun, N E, Walker, D H (2012). “Pathogenesis of Lassa Fever”. Viruses; 4 (12); 2031-2048.
3- Greenky D, Knust B, Dziuban EJ, (May 2018). “What Pediatricians should know about Lassa Virus”. JAMA Pediatrics: 172 (5); 407-408.
4- Goejienbier, Marco; Wagenear Jiri; Goris, Marga Martina; Byron; Heido; Vahen; Hafskeerl, Ruby, Oslerahaus, Albert; Van Gorp, Eric (7 June 2012). Clinical Reviews in Microbiology. 39 (1):26-42.
5- Samuel Daso. “Lassa Fever: What you need to know. PDF from original 25 June 2017.
6- Center for Disease Control and Prevention: Lassa Fever and Symptoms (9 July 2017).