World human plague cases lowest in 30 years, but WHO warns it remains a particularly “formidable epidemic disease”
In just over a month between June 11 and July 15, 2020, the Democratic Republic of the Congo has reported an upsurge of plague cases, particularly in the Ituri province.
The latest disease outbreak bulletin of the World Health Organization (WHO) said the plague-endemic province reported 45 cases of which nine have died already.
On June 12, a 12-year-old girl from the Rethy health zone (a cluster of 11 villages) of the province died with plague symptoms of headache, fever, cough and an enlarged lymph node. According to Congo’s reporting to WHO, more deaths were reported from this girl’s community later with the same suspected plague symptoms.
In the demarcated 22 health areas (tentatively an area under a public health centre) in Rethy, six reported 45 cases, of which nine died by July 22. This puts the fatality rate at 20 per cent.
Plague manifests in three known forms: Bubonic, septicemic and pneumonic. Bubonic plague turns to pneumonic plague if not treated. According to the country nodal Institut National de Recherche Biomédicale laboratory in Kinshasa, of the 45 cases reported, two were of septicemic plague and the rest were of bubonic plague. But the WHO bulletin said all the three types of plague are present in the country now.
Since the beginning of 2020, the Ituri province reported 64 cases of plague, and 14 deaths due to it. During the same period in 2019, the province reported just 10 cases.
Plague — though limited in geography — continues to be a dreaded infection. In 2019, there were 289 cases of human plague reported from across the world.
A study on plague outbreaks in the first decade of the 21st century — published in the American Journal of Tropical Medicine and Hygiene — said the disease affected 21,725 people killing 1,612. The United States reported 57 cases out of which seven died. During 2010-2015, the plague infected 3,248 people killing 584 of them.
In the last one decade, plague cases reduced 10-fold. Of the 33 countries that reported some cases in the past 30 years, only 10 reported human cases in the last five years.
In recent years, the plague outbreak was limited to sub-Saharan Africa, Asia, and North and South America.
In Africa, countries affected by the plague include Congo, Madagascar, Tanzania and Uganda. In the Americas, the affected countries were the US, Bolivia and Peru.
In Asia, China, Kyrgyzstan, Mongolia and Russia reported plague in recent years. Congo and Madagascar account for the majority of plague cases in the world.
“It must be borne in mind that the geographical distribution of human plague is more limited than that of the natural foci of infection, where the plague bacillus circulates in the animal reservoir at low levels,” said Eric Bertherata of the WHO’s health emergencies programme.
The countries most affected are also some of the poorest in the world, where environmental monitoring is very limited or non-existent, according to Bertherata.
“Animal surveillance data where these exist (for example, in the United States), or the occurrence of human cases in previously unaffected areas (in the case of Madagascar), on the contrary, show a general tendency towards geographical extension,” said Bertherata.
“This extension can be linked to anthropogenic modifications of the environment or to the colonisation of new territories, in particular by the black rat,” he added.
Bertherata also spoke to Down To Earth on the issue of anti-microbial resistance (AMR) in plague.
“In theory, AMR for plague is a big issue because all the control strategy is based on early diagnosis and treatment, since the plague vaccine has been abandoned in most parts of the world (Central Asia excepted) and is not recommended by WHO anymore,” he said.
“This vaccine, which had been developed by Pasteur Institute in Madagascar, was a key tool in the control of the disease which was hyper endemic in this country in the 1930s. There were no antibiotics at this time. However, this vaccine could present severe neurological side effects. This is why it was abandoned when antibiotics became widely available,” he added.
Actually and fortunately, cases of resistance of Yersinia pestis, the pathogen that causes plague were very rare and few had been reported in the scientific literature, Bertherata said.
“However, as the risk exists and would have huge consequences, WHO recommends that all the Yersinia pestis strains which are isolated, are tested for AMR. WHO closely follows up its implementation in the endemic countries: this is systematically done and we have no report of resistance in the last 10 years or more,” he added.
Plague usually receives very little attention from the international community and donors, according to the latest WHO status report on the plague, under the International Health Regulations reporting.
“It is not the subject of intensive control programmed in endemic countries,” the report said.
It issues a warning as well: “Plague remains a particularly formidable epidemic disease, especially when its pulmonary form manifests itself in an urban setting.”
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