2020 Plague Outbreak in the Democratic Republic of Congo

By Sheli Malikin and Anikait Panikker

Introduction

In the Democratic Republic of Congo (DRC), the first case of the plague was reported on June 12, 2020 to the health zone of Rethy in which a 12 year old girl was infected. Shortly after being reported, the first patient died and was quickly followed by other members of her community.  From the middle of June 2020 to the middle of July of the same year, cases began to rise. Throughout the DRC, 578 cases were reported while 44 of them resulted in death. The plague is an ongoing epidemic that the DRC is attempting to control through various measures.

Description of the Disease

The plague is a zoonotic disease caused by the Gram-negative bacterium Yersinia Pestis. Depending on the source and progress of the infection, it can be referenced as either the bubonic, septicemic, or pneumonic plague. Bubonic plague refers to a flea bite that transfers the bacterium and begins to propagate as it enters the lymphatic system where it will begin to replicate and cause infection. If the bubonic plague is left untreated, it will begin to progress, becoming the septicemic plague. The septicemic plague can result from direct flea bite or through touch of infected animal, where the bacterium begins to enter the bloodstream. Furthermore, the plague can continue to develop into pneumonic plague where it harms the lungs and is transmittable through human to human contact. A patient will begin experiencing symptoms such as fever, headache, weakness, and swollen lymph nodes (Buboes) (figure 1). Once left untreated, the symptoms will progress to a severe fever, chills, abdominal pain, bleeding into other organs, and tissues may begin to turn black and die (figure 1). If symptoms continue to be untreated, chest pain, difficulty breathing, cough, and rapid development of pneumonia (figure 1) will be experienced. Without proper administration of antibiotics, mortality rate increases to 100%, whereas with the administration, mortality rate decreases to 50%. There are various factors associated with the vulnerability of this disease. For instance, populations living in rural areas, with poor sanitation, and living in the lower economic class are most vulnerable to the exposure of the plague. Furthermore, malnourishment, iron deficiency, and general infections are key factors enhancing vulnerability.

Figure 1: Visual representation of symptoms for each stage of the plague. Source: Public Health Image Library, Center for Disease Control (2020).

Sources of the Outbreak

Yersinia pestis is transmitted from diseased rodents to humans by the bite of fleas carrying the plague bacteria. Additionally, humans may be affected by inhaling contaminated tissues or from direct contact with the infected animal tissue. Therefore, the movement of rats carrying fleas between provinces in the DRC is the primary source of the outbreak. Though initial cases of the modern plague in Congo were discovered in 2005, it is unclear how the first person to become infected with the disease transmitted it. What is solidified is that the unsanitary and poor living conditions many of the population live through are primary drivers for the re-emergence in cases, as it was already an epidemic to begin with. Flea infested rodents come into villages looking for food, allowing the insect to infect domestic animals and livestock before the disease is transmitted onto humans.

Figure 2 shows the intracellular life of how Y. pestis invades skin and eventually evades the immune response triggered by the human body. Since neutrophils, a type of white blood cell that travels to the site of infection to destroy microorganisms, phagocytize foreign bacteria is the first line of defence of the innate immune system, Y. pestis is presumed to be eliminated at this step. However, figure 2 proves that Y. pestis causes a subversion and is able to live past being phagocytized because the bacteria can replicate in the neutrophils itself. From here, along with a combination of other mechanisms deployed by the bacteria, Y. pestis is able to cause critical damage to the human body.

Figure 2: Infection pathway of Yersinia Pestis through the skin barrier and eventually to the lymph nodes once the flea carrying the bacterium infects an individual. Source: Demeure, C., Dussurget, O., Fiol, G., Guern, A., Savin, C. & Cerdá, J. Yersinia pestis and plague: an updated view on evolution, virulence determinants, immune subversion, vaccination, and diagnostics. Genes Immun 20, 357–370 (2019).

Though human to human transmission is nonexistent when it comes to the bubonic plague, it is important to note that this is not the case in regards to the pneumonic plague. A more severe and the most virulent form of plague, the pneumonic plague is a causation of an untreated bubonic plague spreading to the lungs. Figure 3 shows how aerosols infected with Y. pestis are able to facilitate inter-human transmission. In addition to mode of infection, pneumonic plague differs from the bubonic plague from the target tissue, being the lungs as opposed to the skin/lymph nodes as shown in Figure 3. Furthermore, figure 3 exhibits Y. pestis growth is enabled due to the generation of a permissive environment generated during the pre-inflammatory phase.

Figure 3: Portrayal of the inter-human transmission of the pneumonic plague via aerosols infected with Y. pestis and the effect it has on human lungs. Demeure, C., Dussurget, O., Fiol, G., Guern, A., Savin, C. & Cerdá, J. Yersinia pestis and plague: an updated view on evolution, virulence determinants, immune subversion, vaccination, and diagnostics. Genes Immun 20, 357–370 (2019).

Causes of the Outbreak

Considering the plague thrives on poor sanitation and hygiene practices, the living conditions in rural Congo, where one out of six people live in extreme poverty, inevitably increases the rate of infection. Unfortunately, the largest demographic affected by the disease is characterized by their socio-economic status. In fact, poorer families are especially affected negatively considering their lack of wealth directly translates into lack of resources. 

Specifically, there are a plethora of families that sleep on the floor due to the lack of beds, thus aggravating unhygienic living conditions. In addition to poor waste disposal that would eventually attract more rodents, there is a lack of secure options to stock food and livestock. This translates into livestock being cohabitants with their owners under the same roof, which would only serve to increase flea populations in the household. These living conditions only exacerbate the infection rates in the DRC and the lack of resources deployed into the country make countermeasures against the disease more difficult.

Response

Though it is unfortunate that because the DRC is a developing nation, the global community does not focus its attention on eradicating a disease which is of utmost importance. However, international groups like the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) are providing adequate resources in an effort to alleviate plague cases in the Congo. An initial measure taken to end the outbreak was the deployment of a national rapid response team (RRT) to the affected health zone to conduct an outbreak investigation and implement initial response activities. Moreover, the WHO and other local health partners are cooperating with Congo’s health ministry to support response measures like, contact tracing, case identification, and enforcing quarantine measures. In fact, close contacts were given prophylactic, a treatment to prevent further transmission of the disease. 

Even though It is beneficial to see UN agencies partaking in an effort to decrease the amount of plague cases and aid local communities in overcoming this health crisis, the international community needs to play a larger part to ensure complete eradication of this overlooked disease.  

Aftermath

WHO has suggested preventative methods to limit outbreaks such as the increase in surveillance of animal species responsible for the outbreaks If an outbreak within the animal species is detected, action to control the outbreak will be applied, and environmental management programs will be created in order to gain a better understanding for this disease, as well as better communication between each sector involved in the management control of the plague. Furthermore, UNICEF has started a campaign for the extermination of fleas and rodents, as well as ameliorating houses to be more resistant to the entrance of unwanted insects and rodents. They will also be providing beds for children in order to better their living sanitary conditions. Preventative measures were advised to the communities such as washing their hands, keeping up with good hygiene, avoiding animal carcasses and areas experiencing an outbreak within the animal species, as well as, putting emphasis on precautions taken after a flea bite.

References

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