Overview of Black Death—the Plague

On September 13, 2017, the Ministry of Health of the Republic of Madagascar informed the World Health Organization (WHO) of an epidemic situation of pulmonary plague in accordance with the International Health Regulations 2005 (IHR). This epidemic situation is special because of its epidemic scope and urbanization characteristics. Two days ago, a 47-year-old woman in the capital city Antananarivo, was hospitalized due to dyspnea and died, which led to the investigation and discovery of the plague outbreak. According to the investigation, the index case pointed to a 31-year-old man that died in a public taxi on August 27, who transmitted the infectious molecules to other passengers before his death. After traveling to different parts of the country, infected passengers spread the plague. The case indicated all contacts died within 48 hours.

Overview

Plague is a severe infectious disease caused by Yersinia pestis, which belongs to the international quarantine infectious disease, and a natural focus infectious disease mainly prevalent among rodents. Rats and marmots are the natural hosts of Yersinia pestis. Rat flea is the media.

Clinical manifestation

According to the clinical manifestations and the characteristics of plague, it can be divided into light plague, bubonic plague, pulmonary plague, pyemia plague and other types. The incubation period of bubonic plague is usually 2-8 days, that of pulmonary plague is around 2-3 days, and that of vaccination is approximate 9-12 days. Typical symptoms are sudden fever, chills, headache and body pain, weakness, nausea and vomiting. Bubonic plague can cause pain and inflammation in the lymph nodes. Manifestations (sometimes within 24 hours) appear soon after getting infection, which are characterized by severe respiratory symptoms such as shortness of breath and cough, usually accompanied by blood sputum.

Diagnostic

In Vitro Diagnostics (IVD) is nowadays a crucial measure to test infectious microorganisms of plague, which mainly through immunoassay detection of particular antigens and the antibodies produced by the host targeting at specific antigen. The whole workflow starts from antigen tests on the enzyme-linked immunoassay (ELISA) or lateral flow immunoassay (LFIA) platform, aiming to detect microorganisms with pre-coated antibodies.

Conclusion

The country with the most severe plague epidemic is also one of the poorest countries in the world, where environmental monitoring is very limited or nonexistent. In the United States and other regions with surveillance data of plague epidemic, and in areas without plague epidemic before (such as Madagascar mentioned earlier), human cases have occurred, indicating the geographic expansion trend of plague epidemic that may be related to man-made changes in the environment, or to the colonization of new territories, especially the settlement and breeding of black rats. At present, the reported incidence of plague is the lowest in 30 years globally, which is not intensively concerned by the international community and donors, and neither are the plague endemic countries under strengthened control. Therefore, effective detection approaches and related virus infectious diagnostics still remain to be popularized in the above-mentioned areas to avoid the next outbreak of "Black Death".

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