Lassa Fever Spreads Across the Globe


Since January 2016, WHO has been notified of Lassa fever outbreaks in Nigeria, Benin, and Togo, with cases linked to the Togo outbreak in both Germany and Atlanta, Georgia in the United States.

Since January 2016, the World Health Organization (WHO) has been notified of Lassa fever outbreaks in Nigeria, Benin, and Togo, with cases linked to the Togo outbreak in both Cologne, Germany and Atlanta, Georgia in the United States.

Native to West Africa, lassa fever was discovered in 1969 after two missionary nurses died in the town of Lassa, Nigeria. According to the Centers for Disease Control and Prevention (CDC), lassa fever is known to be endemic in Guinea, Sierra Leone, Liberia, and Nigeria, although surrounding regions do experience occasional outbreaks. Of the virus family, Arenaviridae, lassa fever is spread through the urine and feces of an infected Mastomys rodent.

Complications and Symptoms of Lassa Fever

Deafness is the most common complication associated with lassa fever. Deafness occurs in about one third of cases, whether they be mild or severe, and can develop into either temporary or permanent deafness. In addition, an estimated 95% of pregnant women infected with the virus end up having a miscarriage.

Approximately 80% of infections are mild and undiagnosed. Individuals usually develop symptoms of the virus, such as slight fever, general malaise, or weakness, 1-3 weeks after infection. For the 20% of infected individuals who develop severe forms of the disease, symptoms include:

  • Hemorrhaging of the gums, eyes, or nose
  • Respiratory distress
  • Constant vomiting
  • Swelling of the face
  • Abdomen and chest pains
  • Shock
  • Tremors
  • Encephalitis

Only 1% of lassa patients die due to the virus, however, 15-20% of lassa hospitalizations result in death. The number of lassa-associated hospitalization deaths can reach 50% during epidemics.

2016 Lassa Outbreaks in West Africa

Nigeria sees a peak of lassa fever cases on an annual basis between December and February. The country’s latest lassa fever outbreak lasted from August 2015 until January 23, 2016, with four states accounting for 54% of confirmed cases and 52% of reported deaths: Bauchi, Edo, Oyo, and Taraba. A total of 159 suspected cases of lassa fever were reported in the country, including 83 deaths.

Included in the number of cases mentioned above, is 4 lab-confirmed cases of lassa fever in health care workers (of which two have since died).

The WHO office of Nigeria worked closely with the Federal Ministry of Health (MoH) to respond to and contain the outbreaks.

Between January 25 and February 16, 2016, Benin also experienced a Lassa outbreak, with a total of 71 cases and 2 deaths.

More recently, Togo experienced its first two cases of lassa fever. The affected area borders Benin, which lead WHO officials to believe that the infection spread from Benin into Togo territory. Sequencing and epidemiological investigation has ruled out the possibility of viral relation to the Nigeria outbreak, however, further investigation is needed.

Additional Lassa Cases Outside of Africa

In mid-March 2016, WHO was notified by the National IHR Focal Point for Germany of two linked lassa fever cases, the first of which is believed to be an imported case from Togo.

An infected health care worker was stationed in the West African nation before he was evacuated to Cologne. The patient was suffering from complicated falciparum malaria and died from multi-organ failure on February 26, one day after arrival in Germany. The deceased was diagnosed with lassa fever in Hamburg on March 9th after an autopsy revealed hemorrhaging fever.

Prior to the first patient’s lassa diagnosis, a funeral home employee was also infected with the virus after handling the corpse, although the individual was reported to have worn gloves and to not have been exposed to any bodily fluids. The second patient had already exhibited symptoms of an upper respiratory infection before coming in contact with the corpse. The individual had not travelled in the 21 days before falling ill, thus WHO believes the source of infection to be the primary case. This would be the first report of secondary transmission of an imported lassa fever case in Germany. The patient is currently in special quarantine in Frankfurt, along with four family members who volunteered to accompany him in isolation.

Fifty-two contacts of the first patient have been identified, most of whom are health-care workers or funeral home personnel, and are being monitored, along with several of the second patient’s contacts.

Another health worker, a physician’s assistant who had been stationed in Togo, has been admitted to Emory University Hospital in Atlanta, Georgia in the United States, where he was diagnosed with lassa fever. According to CNN, the patient was transported to the Atlanta hospital from Togo at the request of the US State Department. The patient currently resides at the Serious Communicable Disease Unit at the university hospital.

Transmission of Lassa Virus

The lassa virus can be transmitted to humans from the feces or urine of infected Mastymos rodents, which breed frequently and are therefore prevalent in many African savannas and forests. Since these rodents are often found in human homes, specifically areas where food is stored, the development of an infection through the consumption of food contaminated with rat droppings is common. Viral transmission can also occur through direct contact of feces or urine if an individual has open cuts or sores, or through inhaling tiny particles of feces in contaminated air.

In addition, if an individual comes in contact with the blood, tissue, secretions or excretions of an infected individual, human-to-human transmission of the virus is possible. This type of transmission mostly occurs in hospital or clinical care settings where proper personal protective equipment (PPE) is either not readily available or not utilized.

Prevention of Lassa Fever Infection

Since the primary carrier of the lassa virus is Mastomys rodents, the CDC recommends that individuals avoid contact with them. Furthermore, those living in areas where lassa fever is prevalent are advised to store food in rodent-proof containers and keep their homes clean to hinder the entrance of the rats into the home. The CDC also discourages the consumption of rats, since this can cause infection.

To avoid person-to-person infection, individuals are advised to wear protective clothing such as masks, gloves, gowns, and goggles around those known to carry the virus. Those individuals working in hospitals or clinics with known lassa cases should sterilize all equipment and tools. Lassa cases should be isolated from other patients, so as to avoid an outbreak. It is important to educate those living in high-risk regions on the preventive measures they can take to avoid infection.

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