2023-12-15 08:00:00
In 2001, anthrax became infamous for its use as a biological weapon in a series of terrorist attacks. However, epidemiologically relevant outbreaks have been rare: now, however, human cases have increased to numbers never before seen in the African state of Zambia.
An unprecedented epidemic
Just a week ago, the World Health Organization issued an alert echoing the notification of the outbreak by the Zambian National Focal Point of the International Health Regulations (IHR). The first cases were detected in the southern district of Sinazongwe in May this year, coinciding with the death from unknown causes of a large number of wild and domestic animals in the same area, and since then until the end of November 684 cases have been reported. suspected humans and four deaths.
To put the numbers in perspective, the last large-scale epidemic reported in the country occurred in 2011 with a total of 511 suspected cases.
These circumstances have motivated the WHO to launch a strong response mechanism. It is considered that there is a high risk of expansion both within the national territory (there is extensive internal movement of people and animals within the borders of Zambia) and in the region, especially considering that there is little involvement of local communities with the measures taken due in part to the lack of alternatives to handling animals and carcasses as a way of life.
After all, Zambia is a country suffering from high levels of poverty and food insecurity, with poor health infrastructure and availability of vaccines and medicines. All of these factors represent a major obstacle to containing the outbreak.
How anthrax affects people
As the WHO itself points out, anthrax is a disease caused by a spore-forming bacteria called Bacillus anthracis. It is a zoonosis (a disease that is transmitted from animals to humans) that affects ruminant mammals such as cows, sheep or goats.
The mechanism by which anthrax spreads is quite particular, since infections often do not occur from animal to animal or from human to human. Instead, the blood emitted by sick animals contaminates the soil (telluric reservoir), where the spores can retain their germination capacity for years. When spores enter the human body (either via consumption of contaminated animal products, by inhalation, or through cuts or abrasions to the skin) they germinate, multiply, and produce toxins that cause disease.
Depending on the type of exposure, individuals can develop one of three clinical presentations of anthrax, which are:
Cutaneous anthrax: the most common presentation, it takes the form of an itchy lump on the skin in the exposed area that quickly transforms into a black lesion. In some people, headache and muscle pain, fever, and vomiting follow. Gastrointestinal anthrax: The initial signs are similar to those of food poisoning, but worsen to severe abdominal pain, bloody vomiting, and severe diarrhea. Pulmonary anthrax: More severe presentation, its initial symptoms are similar to that of a common cold but can quickly progress to severe respiratory problems or shock.
According to the professor of Microbiology at the University of Salamanca Raúl Rivas in an article in the scientific publication The Conversation, the mortality of the disease can be very high. The main toxins released by the bacteria are dema toxin and lethal toxin that triggers large-scale release of cytokines from macrophages, ultimately causing sudden death.
The risk at a global level
Although this large-scale outbreak is limited to Zambia, the truth is that anthrax is a disease present throughout the world with an annual incidence that varies between 20,000 and 100,000 cases, according to the data provided by Rivas. In countries like Spain, it mainly affects workers who handle animal bodies, their hides, skins, hair, meat or bones. Therefore, it is considered an occupational disease.
On the other hand, one of the most famous aspects of anthrax is that its danger turns the spores into a potential biological weapon; The best-known precedent is the distribution in 2001 in the United States of envelopes with spore powder that infected 22 people and killed five.
Although a priori there does not appear to be a significant threat of an outbreak of global dimensions, it is important that efforts continue in the affected country to stop the transmission of the disease, especially by raising awareness of the local population. Similarly, the WHO recommends international travelers observe regulations regarding the importation of animal products, trophies or souvenirs.
References
WHO. Disease Outbreak News: Anthrax-Zambia. Consulted online at on December 14, 2023.
Raúl Rivas González. Unprecedented anthrax outbreak in Zambia: what danger does it represent? The Conversation (2023). Consulted online at https://theconversation.com/brote-sin-precedentes-de-antrax-en-zambia-que-peligro-representa-219750 on December 14, 2023.
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