Lassa fever facts
- 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. Health workers may be infected by direct contact with blood, body fluids, urine, or stool of a patient with Lassa fever.
- Lassa fever occurs primarily in West Africa in areas where these rodents live.
- Lassa fever outbreaks occur every year. The number of people infected peaks between December and June.
- A large outbreak was reported by the Nigeria Centre for Disease Control that began early in 2018.
What is the history of Lassa fever?
Lassa fever was first described in the 1950s, and the viral particle was identified in 1969 from three missionary nurses who died in Lassa, Nigeria, after caring for an infected obstetrical patient. Lassa fever is one of the hemorrhagic fever viruses, occurring in West Africa sub-regions in similar areas as Ebola virus. Sierra Leone, Liberia, Ghana, and Nigeria are most often affected. Surrounding regions are also at risk, because the rodents that transmit the virus are very common throughout West through East Africa. There are 100,000 to 300,000 cases of Lassa fever each year in the world. Lassa fever heavily impacts Sierra Leone and Liberia in particular, where it causes an estimated 5,000 deaths and about 10%-16% of admissions to hospitals each year. Deaths are especially common in children. Case fatality is 1% in general (compared to 70% in Ebola virus). Severe cases have a case fatality of 15%.
An unusually intense outbreak developed in early 2018 in Nigeria with over 300 confirmed positive cases reported in the month of March. Cases were reported in Bauchi, Plateau, Edo, Ondo, and Ebonyi States. Sixteen health workers, at least four of whom died, were diagnosed as of Mar. 4, 2018. Along with high numbers, case fatality rates for this outbreak exceeded 20%. A Weekly Epidemiological Reporthas been maintained by the Nigeria Centre for Disease Control.
Nigerian Minister of Health, Professor Isaac Adewale, announced that vaccine against Lassa virus would be arriving by the end of 2018. Dr. Chikwe Ihekweazu, CEO of the Nigeria Centre for Disease Control, has stressed the important advances of improved awareness and expanded ability to test for Lassa fever virus in recent years. Dr. Ihekweazu has encouraged improved adherence to infection prevention measures and community sanitation efforts to control current and future outbreaks of Lassa fever. Lassa fever has rarely been diagnosed in the U.S. There have been only six diagnosed cases since 1969. The last case was diagnosed in May 2015, in New Jersey in a patient traveling from Liberia. U.S. cases have involved international travelers or immigrants who arrived with the infection after exposure to rodents in West Africa.
Among the scientists who have studied hemorrhagic fever viruses, Dr. Susan P. Fisher-Hoch, Professor of Epidemiology at the University of Texas School of Public Health, worked extensively with Lassa virus, conducting primate studies and investigating several outbreaks in Nigeria while working with the U.S. Centers for Disease Control and Prevention (CDC). While Deputy Branch Chief of the CDC Special Pathogens Laboratory, Division of Viral Diseases, she supervised the Sierra Leone Lassa Fever Research Unit and published major research articles on Lassa fever vaccines and other hemorrhagic fevers. Many students of epidemiology (the study of how diseases spread) are familiar with the story of her work with her husband, Dr. Joe McCormick, whom she married while he was Chief, Special Pathogens Laboratory, Level 4: Virus Hunters of the CDC. Dr. Fisher-Hoch was elected to the Women in Technology International Hall of Fame in 2008 for her extraordinary contributions to science and medicine.
Lassa Fever Treatment & Medication
Ribavirin (Rebetol, Copegus, Ribasphere, RibaPak, Moderiba)
Ribavirin is an antiviral drug. It is used in combination with interferon for the treatment of chronic hepatitis C. Although the exact mechanism of its action is unknown, it is thought to interfere with the production and/or action of viral DNA and RNA which are critical to the survival and multiplication of the virus.
What are causes and risk factors for Lassa fever?
Lassa fever virus is mainly a zoonosis (a disease that is animal-borne or spread to humans from animals). It is spread to people through contact with household items, food, water, or air contaminated with the droppings or urine of infected multimammate rats (Mastomyces natalensis). These rodents live throughout West Africa in homes, and they can shed this virus without being ill. People most often become infected by inhaling air contaminated with aerosols of rodent excretions, swallowing the virus in food or contaminated utensils, preparing and eating multimammate rats (meat of wild or non-domesticated animals, called bush meat or wild meat, is often prized as a delicacy), and contact with open wounds. Lassa fever virus is believed to be endemic (always present) in Ghana, Sierra Leone, Liberia, and Nigeria. It has also been detected in Ivory Coast, Benin, Guinea, Burkina Faso, Mali, Senegal, Gambia, and Central African Republic. Reporting of cases is not consistent, and the rats are present throughout West, Central, and East Africa, so cases are possible throughout these areas.
Travelers to West Africa staying in homes or areas of poor sanitation or crowding, as well as health care and laboratory professionals serving in health care facilities in West Africa, are most at risk. Infection prevention methods are critical to reducing infection of health care workers and spread within health facilities.
Those at highest risk for serious complications and death are pregnant women in their third trimester. Stillbirth or fetal loss occurs in 95% of pregnancies.
Is Lassa fever contagious? If so, what is the contagious period for Lassa fever?
Person-to-person spread is possible but is not as frequent as with Ebola virus. It can rarely occur upon direct contact with saliva, blood, and bodily fluids and mucous membrane or sexual contact. Casual contact of intact skin with intact skin does not transmit the virus. Laboratory workers and health care professionals can become infected through improper infection-control precautions, and patients in rural hospitals have acquired it through reuse of disposable needles.
No person-to-person spread has been documented in the U.S. from returning travelers..
It is not clear when infected humans are contagious or for how long they are contagious. The presence of virus in the blood is known to peak four to nine days after symptoms begin. The virus can be transmitted in semen for up to three months.
Lassa fever is one of the hemorrhagic fevers and may appear with signs and symptoms like Ebola or Marburg hemorrhagic fever viruses, and until these viruses are ruled out, suspected cases must be managed with infection control precautions to prevent contact with blood, body fluids, and contaminated surfaces. These include basic hand washing or alcohol-based sanitizing between patients. When working within 3 feet of an affected patient, use of additional barrier personal protective equipment should include an impermeable long-sleeved gown, gloves, and face mask with eye protection. Safe injection practices, safe laboratory handling, and safe mortuary procedures are also important.
credit/source: https://www.medicinenet.com/lassa_fever/article.htm#when_is_lassa_fever_no_longer_contagious
Note: All information are credited to the original writer's source and references.
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