Plague

Plague has been associated with several major epidemics and pandemics throughout history and can be a very severe disease in people, with a case fatality ratio of 30 to 60 per cent for the bubonic type, 80 to 90 per cent for the septicaemic plague and almost always fatal for the pneumonic kind when left untreated. Between 2010 and 2015, 3,248 people were infected with plague worldwide, including 584 deaths. Plague is a zoonotic and vector-borne disease found in all continents, except Oceania. Currently, the three most endemic countries are Madagascar, the Democratic Republic of the Congo and Peru.

The following are standard case definitions to allow national health authorities to interpret data in an international context. However, during an outbreak case definitions may be adapted to the local context and the Red Cross Red Crescent should use those agreed/established by national health authorities. NB: Consider that during community-based surveillance, volunteers should use broad (simplified) case definitions (referred to as community case definitions) to recognize most or all possible cases, provide relevant risk communication and appropriate actions and encourage them to seek care. Other actors such as healthcare workers or investigators studying the cause of a disease, on the other hand, can use more specific case definitions that may require laboratory confirmation.

Clinical description: The clinical presentations and the prognostic are closely linked to the form of plague: disease characterized by rapid onset of fever, chills, headache, severe malaise, prostration, WITH extreme painful swelling of lymph nodes (bubonic form) OR cough with blood-stained sputum, chest pain, difficult breathing (pneumonic form); both forms can progress to a septicaemic form with toxaemia: sepsis without evident buboes rarely occurs.

Laboratory criteria for diagnosis: Confirmation of plague requires laboratory testing. Isolation of Yersinia pestis in cultures from buboes, blood, cerebrospinal fluid (CSF) or sputum OR detecting specific Yersinia pestis antigen using different techniques.

Case classification

Suspected: Any person meeting the clinical criteria with at least one epidemiological criteria.

Bubonic plague: Fever AND sudden onset of painful lymphadenitis

OR

Pneumonic plague: Fever AND at least one of the following three:

cough, chest pain, coughing blood.

Probable: Any person meeting the clinical criteria with at least one of the laboratory criteria for a probable case (positive direct fluorescent antibody (DFA) test for Y. pestis in clinical specimen OR passive haemagglutination test, with antibody titre of at least 1:10, specific for the F1 antigen of Y. pestis as determined by the haemagglutination inhibition test (HI) OR epidemiological link with a confirmed case.)

Confirmed: A suspected or probable case that is laboratory-confirmed.

WHO case definition source of information: https://www.who.int/docs/default-source/outbreak-toolkit/latest-update---11-october/plague-disease-outbreak-toolbox---25092019.pdf?sfvrsn=71fecab_2

Integrated Diseases Surveillance and Response in the African Region: Technical Guidelines for Integrated Disease Surveillance and Response in the African Region: Third edition | WHO | Regional Office for Africa

One confirmed case is sufficient to identify potential outbreak, but this needs to be interpreted in context. (e.g. confirmed pulmonary plague case in urban context requires immediate intervention).

• There is a risk of human plague wherever the presence of plague natural foci (the bacteria, an animal reservoir and a vector) and human populations co-exist. For more details see: http://www.who.int/csr/disease/plague/Plague-map-2016.pdf?ua=1)
• Outbreaks of the disease are of particular concern when they occur in settings where access to antibiotic treatment and early care is difficult, as in overcrowded settings.
• Lack of appropriate sanitation and hygiene measures, including rodent control. Households where food is not stored appropriately or trash is not managed well are environments that may attract rodents, therefore increasing the risk of transmission in areas where the bacteria are present in rodent populations (endemicity).
• During epizootics (outbreaks of epizootic diseases), humans are at high risk of transmission when rodents die in large numbers, attracting fleas that may afterwards bite humans. When fleas and rodent populations increase, the risk for epizootics increases as well; therefore controlling rodent host populations is an important prevention strategy.
• Ecological disruptions forcing large numbers of rodents into human populations (e.g. habitat destruction during deforestation, or conflict)
• Pneumonic plague: people in close contact to patients such as caregivers and healthcare workers who do not use correct infection prevention measures are at increased risk.

Attack rates will vary from one outbreak to another. In case of an outbreak, consult the latest information provided by health authorities.

In recent epidemics the secondary attack rate has varied between 14—75 per cent (note different transmission routes for bubonic and pulmonary plague: the attack rate is directly linked to the route of transmission and the form of plague. It is low for bubonic plague transmitted through rodents. It can be very high for pneumonic plague transmitted from person-to-person.).

• People with weakened immune systems.
• Immunosuppressed persons such as those receiving chemotherapy,  transplant recipients or HIV carriers.
• People with chronic diseases such as renal disease, cancer, chronic lung or liver disease, and diabetes.

Yersinia pestis bacterium (Y. pestis).

Vector: fleas, particularly Xenopsylla cheopis (oriental rat flea) carrying the bacterium Y. pestis.

Zoonotic disease: rodents, some other animals like prairie dogs, squirrels, rabbits, cats.

• Vector-borne: Bites of infected fleas (typically for bubonic plague, and  septicaemic plague), particularly Xenopsylla cheopis (Oriental rat flea).
• Contact transmission: Touching or skinning infected animals (such as prairie dogs, squirrels, rats and rabbits) (for bubonic plague and septicaemic plague). Some evidence exists that plague can be transmitted by intensive handling of the corpse or carcass.
• Vehicle-borne transmission: Y. pestis is transmitted to humans via contact with food or household items contaminated with infected animal bodily fluids, or (for pneumonic plague) human respiratory droplets.
• Droplet spread: Inhaling respiratory droplets from the cough or sneeze of a person or animal with pneumonic plague.

• One to seven days for the bubonic plague.
• The incubation period for septicaemic plague is not well defined but likely happens within days of exposure.
• Few hours (as little as 24 hours) for the pneumonic plague.

Bubonic plague (the most common form) is not transmitted from person to person. Only humans with pneumonic plague can transmit the infection to others. Patients with pneumonic plague in the final stages of disease pose the highest risk of infection.

• Sudden onset of fever, chills, head and body aches and weakness, vomiting and nausea.
• Bubonic plague: one to two days after, lymph nodes become inflamed, tense and painful; they can turn into open sores with a discharge.
• Septicaemic plague: abdominal pain, shock, and possibly bleeding into the skin and other organs. Skin and other tissues may turn black and die, especially the fingers, toes and the nose.
• Pneumonic plague: rapidly developing pneumonia with shortness of breath, chest pain, cough and sometimes bloody or watery mucous; it may cause respiratory failure and shock.

Anthrax, bacterial pneumonia, COVID-19 disease, bacterial sepsis, brucellosis, Rocky Mountain spotted fever and other infections.

• Identification of Y. pestis in a sample of fluid from a buboe (painful swollen lymph nodes), blood or sputum.
• Rapid dipstick tests have been validated for field use to quickly screen for Y. pestis antigen in patients.

Please refer to the appropriate local or international guidelines for clinical management. All clinical management including the administration of any treatment or vaccine should be conducted by health professionals.

• Pneumonic plague is invariably fatal unless treated early, but even bubonic plague has a case fatality ratio of 30—60 per cent without treatment, so early diagnosis and treatment is essential for survival and the reduction of complications.
• Antibiotics and supportive therapy are effective against plague if patients are diagnosed in time, with a fatality rate of under two per cent.
• Pneumonic plague patients must be isolated and cared for by trained medical staff with personal protective equipment. Prophylaxis should be provided to close contacts of a pneumonic plague patient.
• The World Health Organization (WHO) does not advise vaccination, except for high-risk groups such as laboratory personnel or healthcare workers.

Individuals who survived a plague infection are considered to have acquired immunity against subsequent reinfection of Y. pestis.