Lassa fever outbreaks

Lassa Fever: Causes, Symptoms and Treatment

Lassa fever is an acute viral infection disease just like other hemorrhagic fever viruses such as Ebola virus, Marburg virus, etc. However, it is not as contagious and deadly as Ebola virus disease. It is caused by a type of rat known as Mastomys to humans when they come in direct contact with their feces or urine in any way. This rat is very common in West Africa so for the obvious reason, it is the highest victim of this disease.

Health workers may contract this infection through direct contact of body fluid, blood, urine or stool of a patient affected with this infectious disease. The Lassa fever outbreaks happen each and every year and the period between December to June is considered its peak season. However, a very big outbreak notified by the Nigeria Centre for Disease Control that begin early of the year 2018.

It is often fatal arenavirus infection as it can cause multiple organ failure including kidney, liver or spleen. Being a hemorrhagic fever it has the power to cause bleeding however in most cases people infected with this virus do not develop any symptoms.

One report suggests that every year approx. 100000 to 300000 cases of Lassa fever came into the picture in West Africa out of which 5000 approximate deaths occur by this disease. Apart from this in some regions of Liberia and Sierra Leone, about 10 to 16% of total hospitalization cases are caused by the Lassa fever disease. This shows how seriously it has impacted these areas.

Also, the disease contains a high risk of the international spreading of this virus. In the year 2015, a case came into the picture where a person returning from Liberia to the U.S. diagnosed with Lassa fever. That means international traveling is quite risky to the outbreak countries especially in the peak season of this hemorrhagic fever disease

What is Lassa Fever?

Lassa fever is an infectious disease that is caused by an Arenaviridae family virus known as Lassa virus. It is a single-stranded RNA hemorrhagic fever virus. This acute febrile viral illness lasts for one to four weeks time. West Africa and some nearby areas of this country are the highest victims of this viral illness.

It was first discovered in Nigeria in the year 1969 when the cases of two missionary nurses came into the picture who was severely ill with a virus infection. Lassa village was the region where it was first documented which also been the reason behind naming it so. This virus is carried by the multimammate rat, Mastomys natalensis which is abundant in equatorial Africa and some nearby regions.

This viral illness mainly occurs in Guinea, Nigeria, Liberia, and Sierra Leone. The Mastomys natalensis rats are also common in neighboring countries of West Africa so they are also at risk of developing this viral illness.

Is Lassa fever a Contagious Illness?

Lassa fever outbreaksLassa fever is contagious but not as much as the Ebola virus can be in terms of number and speed. Human to human spread is possible with this illness but the frequency rate is not very high as with other common hemorrhagic fevers. The contraction rate with direct contact of saliva, bodily fluids, blood, mucus membrane and sexual interaction with the infected person is rare. Also, it is not transmitted through any casual contact of your intact skin with intact skin.

However, the risk of spreading this virus remains in people who are working in a healthcare unit or laboratory workers if they avoid using, or improper usage of infection controlling precautions. Also an already hospitalized patient, especially in rural hospitals, can get this virus through reuse of a disposable needle.

When an infected person will be contagious, and for how long they will remain contagious is not fully clear. However, the quantity of virus in the blood remains in its peak position in between four to nine days from the date of its symptoms initiation. The virus can be transmitted through semen to a healthy person’s body for as long as three months’ time.

This hemorrhagic fever occurs with symptoms similar to Ebola and Marburg hemorrhagic fever viruses. Until these viruses infections are identified it is important to use infection control precaution measures to avoid direct contact with blood, body fluids of the suspected patients as well as contaminated surfaces.

Basic hygiene measures should be followed by each and every individual to avoid the contraction risk of this acute virus disease such as washing hands too frequently with soap and water or using alcohol-based sanitizer, especially by the healthcare workers before and after handling the suspected patients.

Though it is not yet clear when an infected person gets contagious and for how long period, but the virus gets cleared from the patient’s blood during their recovery phase approximately three weeks after the onset of the symptoms.

Incubation Period for Lassa fever

The incubation period for Lassa fever is not fixed. It varies from six days to three weeks’ time. In most of the cases, the Lassa fever patient develops mild to no symptoms at all. As per the British Research team, the incubation period for this illness vary from seven to ten days time and in some cases, it can last up to 21 days time.


The causes of Lassa fever include the following-

  • Once the Mastomys rat infected with the Lassa virus since then it excretes the virus in its urine and feces potentially for the whole life.
  • An infected Mastomys rat can spread this virus easily wherever it lives. These rats breed rapidly and inhabit human houses so the path of getting virus transmission from this infected animal to human beings opens up easily.
  • The Lassa Virus disease occurs due to inhalation or consumption of rat feces or urine. Apart from these viruses can transmit through open sores and cuts.
  • The infected virus can easily contaminate foodstuffs as it inhabits human houses. So when these contaminated foods are eaten the person gets infected with this virus disease. Also, some people eat the rats, in that case, the virus can spread during the cooking process.
  • Human to human transmission of this virus is possible through direct contact of infected person’s blood, tissues, secretions, and excretions but not through touch. Also, it is transmitted through sexual interaction from an infected person to their healthy sexual partner.
  • The Lassa virus transmission is possible through sharing needles like in the cases of drug addicts. In a healthcare unit reuse of a needle can also spread this virus in a healthy person’s body.
  • In a poorly equipped hospital or healthcare unit where the protective clothing and sterilization is not the standard one, the transmission of Lassa fever is possible between patients and healthcare workers.


The symptoms of Lassa fever usually develop within 6 to 21 after the contraction of this infection. However, at approx. 80% of cases of this infection, the patient does not develop any vital symptom. Still, there could be general discomforts such as headache, slight fever, and malaise. The remaining 20% of cases of this infectious disease, the patients develop serious symptoms including-

  • Difficulty in breathing
  • Bleeding occurs in nose, eyes, gums or any other area in the body
  • Bloody diarrhea and vomiting
  • Swollen airways
  • Difficulty in swallowing
  • Coughing
  • Pain in the chest, back, and abdominal area
  • Shock
  • Swollen face
  • Hearing loss that can be permanent
  • Abnormal heart rhythm
  • Swelling occurs in the sac surrounding your heart known as Pericarditis
  • High or low blood pressure level
  • Meningitis
  • Tremors
  • Seizures
  • Encephalitis

About 1 percent of all Lassa fever cases are fatal one and approx. 15 to 20 percent of all hospitalization cases end up with the patient’s death. In the cases of death, it occurs usually within two weeks after the onset of the symptoms in patients because of multiple organ failure. 1 Out of every 3 cases of Lassa fever, patients develop hearing loss problems which is the most common complication of this disease.


Apart from acute illness, hearing loss is the most common complication associated with Lassa fever which occurs as after effect of this illness. In 20 to 30 % of cases of Lassa fever, the acute deafness problem has been recognized in the patients during their recovery period. One study report suggests that the Lassa fever virus is the most common reason behind sudden deafness in the outbreak areas. This is because in most cases people do not develop any symptoms plus researches show that people with acute deafness found containing high antibody levels to Lassa virus which suggests the existence of a recent infection.

This commonly occurred compaction of this virus fever varies in its intensity or severity. However how intense this complication could be, do not always depend on the severity of symptoms caused by the Lassa fever. The deafness caused by the Lassa virus is usually total not partial one and for the lifetime.

Women who are in the third trimester of their pregnancy have a high risk of complications if they contract this virus during this phase. In 95% of cases of pregnancy, spontaneous pregnancy loss incident occurs as a result of this disease.


As the symptoms of Lassa fever vary excessively and in some cases, people do not develop any remarkable symptom so its diagnosis is very difficult. The symptoms which generally occur with this viral fever resemble other viral hemorrhagic fevers such as Ebola virus, typhoid, and malaria.

Laboratory-based tests are the only reliable sources to diagnose this fever however handling the specimens is quite risky as it can be hazardous.  So, only well recognized, specialized institutions are authorized to conduct this laboratory test for diagnosing this virus fever.

  • Enzyme-linked Immunosorbent Serologic Assays (ELISA) – This is a laboratory test that helps in detecting Lassa antigen, Lassa IgM and IgG antibodies. However, this virus can grow in culture within 7 to 10 days. So for the definitive result, another testing is available that can prove effective for a concluding result known as Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) assay. However, this testing is limited to research.
  • Immunohistochemistry Stains- This testing is performed on tissue specimens for diagnosis of the Lassa fever. It is also effective for postmortem diagnosis.


Early-stage diagnosis of Lassa fever can reduce and prevent the infected patient’s death risk and other complications with timely treatment. Rehydration and treatment for improving patient symptoms help in curing this hemorrhagic fever. Ribavirin an antiviral prescribed drug has been proved effective in fighting with the Lassa virus attack.

However, it is not clear how this particular drug works. The study report says that if this medicine prescribed early in the cases of serious illness caused by this virus fever, it can reduce the patient’s mortality risk from 50% to 5% which is really amazing. Negative impacts include hemolytic anemia or rupture of red blood cells if it is infused very fast.

However, the availability of this medication is very limited in the highly affected areas of this virus. Apart from this, the usage of Ribavirin is associated with the risk of creating toxicity and teratogenic that means it may cause mutations. This is the reason why it is not considered as an ideal solution for the treatment of Lassa fever.

Also, this drug is not beneficial for preventing the occurrence of Lassa fever. There is no particular vaccine present currently for preventing this illness risk. However, researches for developing a vaccine for Lassa fever is in its ongoing process and shows hope for promising results in the future.


The Lassa fever outbreak can be prevented highly by focusing on community hygiene to control the growth of the rat population in the affected countries. Some effective prevention measures are enlisted below-

  • Washing hands frequently with soap or hand wash and water
  • Keeping the home area clean and garbage-free
  • Storing the consumable food products in rodent-proof containers only
  • Keeping pet cats to kill rodents
  • While taking care of a sick family member make sure you avoid direct contact with their blood and other bodily fluids
  • Safe burial procedures should be conducted for a person died of Lassa fever disease
  • Safe protective gears like gloves, long-sleeved gown, eyewear, masks, etc should be used by the healthcare workers while handling an infected patient within 3 feet of distance in a healthcare setting
  • Safe injection practices should be followed including safe disposable of used injections
  • Laboratory specimens should be handled carefully

The Mastomys rats are so widespread that its complete eradication is very tough. The focus remains to avoid these rodents inhabitation in human houses. The World Health Organization and other health organizations working hard to raise awareness regarding Lassa fever outbreaks including recent improvement in treatment techniques, prevention measures, etc.

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