People can get lassa fever through people with lassa fever are not believed to be contagious before they. Treatment of infected patients since the initial observation in 1969 of the. The disease is limited to west africa where most cases are found in poor, rural villages. Etiology lassa virus l asv is a bisegmented, negativesense, single stranded rna virus belonging to the old world complex, genus arenavirus, family arenaviridae. Lassa fever is caused by a virus that is found in west africa. The virus is spread by a rat that lives in large numbers in west, central, and east africa. Sep 15, 2017 lassa fever lf is a severe and often fatal hemorrhagic disease caused by lassa virus lasv, a member of the arenaviridae virus family. Pdf immunobiology of ebola and lassa virus infections. We tested favipiravir in lassa virus viremic macaques and found that 300 mgkg daily for 2 weeks successfully treated infection. You are advising a public health department in africa regarding detection and management of an outbreak of lassa fever lf. Only 1% of all lassa virus infections overall are fatal. Lassa virus, the causative agent of lassa fever, an important hemorrhagic disease of west africa.
Upon infection, once the virus rnp is delivered into the cytoplasm of the. Improving the breadth of the hosts immune response to. Introduction to lassa fever world health organization. Infected humans can spread the virus to each other through contact with contaminated objects or blood. Vertical transmission from mother to child has been. Persontoperson infections and laboratory transmission can also occur, particularly in the. This pathogenesis study evaluated the temporal progression of disease in guinea pigs following. Lassa virus lasv like the ebola virus is zoonotic in nature i. Jun 27, 2014 lassa virus, which spreads from rodents to humans, infecting about half a million people every year, can lead to deadly hemorrhagic fever. Use of favipiravir to treat lassa virus infection in macaques cdc. Secondary human to human spread within a community may occur through inhalation or ingestion. Other neighboring countries are also at risk because the type of rat that spreads the virus is also found.
High crossreactivity of human t cell responses between. Prognosis and evolution of lassa virus infected persons. Less commonly there may be bleeding from the mouth or gastrointestinal tract. Clinical sequencing uncovers origins and evolution of lassa virus. Lassa virus, a member of the arenaviridae family old world or lassa lymphocytic choriomeningitis virus lcmv serogroup, is transmitted from a natural rodent reservoir, mastomys natalensis, to humans via contaminated rodent excreta or by close contact with infected individuals. Sequence variability and geographic distribution of lassa. There is a need for more information on kinetics of lassa virus detection in blood and nonblood samples to correctly identify all infected patients in different stages of the disease. Strain guinea pigs were uniformly susceptible to lethal infection by 2 or more pfu of lassa virus strain josiah.
The animal reservoir is the rodent multimammate rat mastomys natalensis. Mastomys rodents shed the virus in urine and droppings and direct contact with these materials, through touching soiled objects, eating contaminated food, or exposure to open cuts or sores, can lead to infection. Lassa fever killed two missionary nurses stationed in the region lassa town where the disease was first discovered. Laboratory diagnosis of lassa fever journal of clinical. It is usually transmitted by the mastomys natalensis multimammate rat. Typically, lassa virus causes a persistent infection of rodents, and the human index case usually results from infection with virus shed by rodents in their urine or other excretions. An estimated 100,000 to 300,000 infections of lassa fever occur annually, with approximately 5,000 deaths. Lassa virus infection in experimentally infected marmosets. Although lf is likely underreported in this area, an oftencited report concluded that between. Lassa antibody and antigen were found in 96 11% and 46 5%, respectively, of 884 tested mastomys demby et al.
Epidemiologic and clinical features of lassa fever outbreak. Lassa virus remains an important cause of illness in west africa and among the travelers returning from this region with an acute febrile illness. The lassa virus is transmitted to humans mainly through handling rats, food or household items contaminated by rats urine and faeces. Most human infections result from zoonotic transmission. Current research for a vaccine against lassa hemorrhagic fever virus bryce m warner,1 david safronetz,2 derek r stein2 1department of medical microbiology, university of manitoba, winnipeg, mb, canada. People can get lassa fever through people with lassa fever are not believed to be contagious. This requirement sheds light on the enigmatic resistance of bird cells. The virus is c losely related to other old world arenaviruses including lymphocytic choriomeningitis and lujo viruses. Following an incubation period of 7 to 18 days, the disease is. Lassa virus, the causative agent of lassa fever, is a member of the family arenaviridae. Laboratory diagnosis of lassa fever vanessa raabe,a jeffrey koehlerb. Lassa fever is one of the hemorrhagic fever viruses like ebola virus, marburg virus, and others unlike ebola virus, lassa fever is not as contagious person to person, nor as deadly lassa virus is typically transmitted by the urine or feces of mastomys rats to humans.
The virus can spread between people throughdirectcontactwiththebodyfluids of a person infected with lassa fever, as well as contaminated bedding and clothing. Hotspots are also suggested to exist for lassa virus lasv, an arenavirus that causes lassa haemorrhagic fever lf in humans 11. The large amount of novel genomic diversity of lassa virus observed in the liberian cases emphasises the need to match deployed diagnostic capabilities with locally circulating strains and underscores the importance of evaluating crosslineage protection in the development of vaccines and therapeutics. Determining ribavirins mechanism of action against lassa. A class of novel, highly divergent arenaviruses, properly known as reptarenaviruses, have also been discovered which infect snakes to produce inclusion body disease. For example, emmerich and colleagues evaluated the anti lassa virus antibody response in a human sample set from west africa by immuno. Lassa virus lasv infection causes an acute, multisystemic viral hemorrhagic fever that annually infects an estimated 100 000 to 300 000 persons in west africa. Lasv, which primarily causes infection in humans, was originally isolated from a missionary nurse in lassa, nigeria in 1969. Apr 20, 2016 lassa virus is zoonotic and infected rodents in the mastomysnatalensis species complex are reservoirs capable of excreting the virus through urine, saliva, excreta and other body fluids to man 7, 11. The multimammate rat mastomys natalensis is the only known reservoir of lasv. The very diverse lasv genome has 4 major lineages associated with different geographic locations. The number of lassa virus infections per year in west africa is estimated at 100,000 to 300,000 with approximately 5,000 deaths. The illness was discovered in 1969 and is named after the town in nigeria where the first cases occurred.
Who target product profile for lassa virus vaccine june 2017. Lassa virus was and continues to be the major cause of hemorrhagic fever in western africa, infecting roughly 400,000500,000 individuals per year and yielding a death rate of 30,00040,000. Lassa virus, an old world arenavirus family arenaviridae, is the. Lassa fever is a viral illness that typically occurs in west africa. Lassa virus entry requires a triggerinduced receptor switch. Scientificepidemiologic evidence regarding blood safety. In contrast, no more than 30% of the hartley guinea pigs died regardless of the virus dose. The occurrence of persontoperson transmission via close contact with infected blood, body. Jan 05, 2020 lassa virus consists of four lineages, three of these lineages are located in nigeria, while the other can be found in guinea, liberia, and sierra lione. Lassa fever, also known as lassa hemorrhagic fever lhf, is a type of viral hemorrhagic fever caused by the lassa virus. O human infection with lassa virus is a severe, gen data have suggested that mild or subclinical infeceralized disease described as lassa fever 1. We used reverse transcription pcr and resequencing microarrays. Epidemiologic and clinical features of lassa fever outbreak in nigeria, january 1may 6, 2018. It was first discovered in 1969 in lassa, nigeria when two missionary nurses died.
Author summary lassa virus lasv, the causative agent of the hemorrhagic illness lassa fever lf, is found throughout west africa. How to safely ship human blood samples from lassa cases within a country by road, rail and sea pdf, 1. Over several decades, importation of lassa fever into. Pdf two of the most important contemporary emerging viruses that affect human health in africa are ebola virus ebov and lassa virus.
Infection with lasv can lead to acute lassa fever lf with symptoms similar to evd. Introduction to lassa fever generic presentation pdf, 1. Lassa mammarenavirus is an emerging virus and a select agent, requiring biosafety level 4equivalent containment. Thin section electron microscopy of infected cell culture. Natural history of aerosol induced lassa fever in non. It is transmitted to humans from contacts with food or household items contaminated with rodent excreta. Lassa virus, a member of the arenaviridae family, can cause viral hemorrhagic fever vhf. You cannot get lassa fever through hugging, shaking hands or sitting near someone. Though a rodentborne infection, it can also be transmitted from person to person during the care of sick relations or more commonly in health care settings as a nosocomial infection. Lassa virus consists of four lineages, three of these lineages are located in nigeria, while the other can be found in guinea, liberia, and sierra lione. Assessing the spatial distribution of lassa virusinfected rodents in rural villages of guinea. These emerging viral hemorrhagic fevers are presumed to be animal borne zoonotic and can be transmitted to humans through contact. When the immune system fails to control the virus, disease is more acute and leads to death. The virus can spread between people through direct contact with the body fluids of a.
Many of those infected by the virus do not develop symptoms. A historical look at the first reported cases of lassa fever. The multimammate mouse mastomys natalensis is the only known nonhuman host for lassa virus monath et al. Lassa fever is caused by infection with the lassa virus. The mortality rate among hospitalized lf cases is high and no effective treatments or vaccines exist. The virus is spread by contact with excretions or materials contaminated with the excretions of an infected rodent or inhalation of contaminated dust and bite wounds. It was first described in northeastern nigeria in 1969, and it is endemic in west africa 1. This information will be important in the development of better diagnostic tests for lassa virus detection in various intended use settings. The natural reservoir for lassa virus is the african. Abstract lassa fever is a viral hemorrhagic fever caused by lassa virus lassa mammarenavirus, a negativesense singlestranded rna virus of the arenaviridae family. How lassa and ebola are similar but different msnbc.
Baseline mapping of lassa fever virology, epidemiology and. The lassa virus is transmitted to humans mainly through food or household items contaminated by infected rats urine and faeces and by handling infected rats. Lassa fever is a zoonotic disease that commonly manifests as an acute viral hemorrhagic fever. Rarely seen in the united states, lassa virus is a cdc category a biological agent inasmuch deliberate aerosol exposure can have high mortality rates compared to naturally acquired infection. Humans are usually infected after contact with infected rodent excreta or aerosolized virus. Mastomys rats infected with lassa virus do not become ill, but they can shed the virus in their urine and faeces. Lassa virus isolation from mastomys natalensis rodents. Like ebola virus, lassa virus lasv can cause hemorrhagic fever with high case fatality rates. Thin section of virions in a space between cells lassa virus buds from the surface membrane of cells where it is then free to invade other nearby cells and is free to enter the bloodstream. Lassa fever is a zoonotic disease, meaning that humans become infected from contact with infected animals. How to safely collect blood samples by phlebotomy from patients suspected to be infected with lassa. The animal reservoir, or host, of lassa virus is a rodent of the genus mastomys, commonly known as the multimammate rat. Viral hemorrhagic fevers lassa, marburg, ebola, crimean.
This is a representation of lasv viremia in relation to lassa virus disease outcomes and immune responses to lassa virus based on published data about rodent, nonhuman primate and human infections. Treatment of lassa fever is primarily supportive, although ribavirin has shown limited efficacy if administered early during infection. Lassa virus lasv is endemic to parts of west africa and causes highly fatal hemorrhagic fever. Use of favipiravir to treat lassa virus infection in macaques. Detection of lassa virus, mali article pdf available in emerging infectious diseases 167.
Lassa virus is typically transmitted by the urine or feces of mastomys rats to humans. Veterinary pathology temporal progression of lesions in. Lassa fever is a hemorrhagic illness caused by lassa virus. Transmission of lassa virus to humans occurs most commonly through ingestion or inhalation. To allow study of infection by lasv under bsl2 conditions, we generated a recombinant virus in which the lasv glycoprotein gp was placed on the backbone of lymphocytic choriomeningitis virus lcmv cl nucleoprotein, z and polymerase genes rlcmv cllasv gp. Lassa fever has caused quite a few epidemic outbreaks in several west african countries. Infection from lassa virus can occur all through the year but peaks in the rainy season, november to april. Lassa virus lasv is a member of the old world complex of viruses, genus arenavirus, family arenaviridae, which also includes lymphocytic choriomeningitis virus lcmv and lujo virus. Oldstone, madeleine rose oldstone, in ebolas curse, 2017. Lassa fever occurs primarily in west africa in areas where these rodents live. Lassa virus entry requires a triggerinduced receptor. Feb 06, 20 lassa fever lf is an acute and sometimes severe viral hemorrhagic illness endemic in west africa.
The animal reservoir of the lassa fever virus is a rat, mastomys natalensis. These viruses infect rodents and occasionally humans. Lassa fever is an acute viral haemorrhagic illness caused by lassa virus, a member of the arenavirus family of viruses. An arenavirus is a bisegmented ambisense rna virus that is a member of the family arenaviridae. Lassa virus is one of more than 25 causative viruses of viral hemorrhagic fever table 4. Case of human lassa virus infection with robust acute t. The lassa virus is transmitted to humans mainly through handling rats, food or house hold items contaminated by rats urine and faeces. A rodent model for human lassa fever was developed which uses inbred strain and outbred hartley guinea pigs. Lassa virus, the cause of lassa fever in humans, is endemic to west africa. Jan 25, 2020 the lassa fever international conference presented an opportunity for the scientific community to reflect on what is known about the lassa virus, identify gaps that exist and prioritise a research.
Lassa fever is a viral disease that belongs to the group of virus diseases causing hemorrhagic fevers, mainly in west africa 1. It is endemic in west african countries, especially sierra leone, the republic of guinea, nigeria, and liberia, where the annual. When symptoms occur they typically include fever, weakness, headaches, vomiting, and muscle pains. Lassa fever was first recognized in lassa, nigeria, in 1969 and is endemic to west africa. Assessing the spatial distribution of lassa virus infected rodents in rural villages of guinea joachim marien a, giovanni lo iacono b, toni riegerc, nfaly magassoubad, stephan gunther c and elisabeth fichetcalvetc adepartment of clinical sciencesoutbreak research team, institute of tropical medicine, antwerp, belgium. Lassa fever full recovery without ribavarin treatment. Pdf lassa virus lasv is responsible for a type of acute viral haemorrhagic fever referred to as lassa fever. Health workers may be infected by direct contact with blood, body fluids, urine, or stool of a patient with lassa fever. It is endemic in west african countries, especially sierra leone, the republic of guinea, nigeria, and liberia, where the annual incidence of infection is between 300,000 and 500,000 cases, resulting in 5,000 deaths per year. Mar 20, 2018 lassa fever lf is a zoonotic disease associated with acute and potentially fatal hemorrhagic illness caused by lassa virus lasv, a member of the arenaviridae family. Pathogenesis of lassa virus infection in guinea pigs.
The symptoms of lassa fever can be nonspecific and mimic those of other endemic infections, especially early in illness, making a clinical diagnosis difficult. They carry the virus in their urine and droppings and live in homes and areas where food is stored. Current research for a vaccine against lassa hemorrhagic. Lassa fever virus lasv causes acute viral haemorrhagic fever with symptoms similar to those seen with ebola virus infections. Improving the breadth of the hosts immune response to lassa. Like many viruses, lassa virus binds to cell surface receptors.
370 101 200 192 1020 345 820 357 1293 733 515 190 149 1387 973 475 818 1231 947 1582 204 108 1471 1182 146 276 1513 1307 5 557 233 1512 281 679 528 1009 477 1357 1119 1319 1335 1331 819 22