The World Malaria Report, the World Health Organization's (WHO's) regular update on the status of malaria worldwide, reveals a global increase in the incidence of the disease in 2022. Estimates indicate an increase of 5 million cases to reach a total of about 249 million cases.
In addition to the traditional challenges associated with the disease, such as the increased resistance of parasites to antimalarial drugs and the lack of financing for research, the document also shows evidence that climate change has further influenced the epidemiological situation.
"The changing climate poses a substantial risk to progress against malaria, particularly in vulnerable regions. Sustainable and resilient malaria responses are needed now more than ever, coupled with urgent actions to slow the pace of global warming and reduce its effects," said Tedros Adhanom Ghebreyesus, PhD, WHO director-general, in a press release announcing the report.
The report observed that changes in temperature, humidity, and rainfall can influence the behavior and survival of the malaria‑carrying Anopheles mosquito.
Climate variability is expected to have indirect effects on malaria trends through, for example, reduced access to essential malaria services and disruptions to the supply chain of insecticide‑treated nets, medicines, and vaccines.
"Population displacement due to climate‑induced factors may also lead to increased malaria as individuals without immunity migrate to endemic areas," according to the report.
Extreme weather events, such as storms and heat waves, can also affect disease transmission. The report cited the catastrophic flooding in Pakistan as an example.
"In 2022 and 2023, extreme monsoon rainfall affected many parts of Pakistan, with evidence suggesting that the severity of the monsoon season was heightened by climate change. This flooding led to a large malaria epidemic that increased the malaria cases in the country by fivefold, compared with the year before," said the report.
The WHO pointed out that the global status of malaria has also been affected by other factors, including the pandemic, which significantly disrupted malaria services, treatment, and diagnosis worldwide.
"It is crucial to recognize the multitude of threats that impede our response efforts. Climate variability poses a substantial risk, but we must also contend with challenges such as limited healthcare access, ongoing conflicts and emergencies, the lingering effects of COVID‑19 on service delivery, inadequate funding, and uneven implementation of our core malaria interventions," said Matshidiso Moeti, MD, WHO regional director for Africa.
Since 2015, malaria cases have increased; the largest annual increase of 11 million cases was estimated between 2019 and 2020.
Pakistan saw the largest increase, with about 2.6 million cases in 2022, compared with 500,000 in 2021. Significant increases were also observed in Ethiopia, Nigeria, Papua New Guinea, and Uganda.
The Situation in Brazil
Malaria cases have declined by 64% in the WHO Region of the Americas in the past two decades, while deaths have decreased by 60% in the same period.
The region's progress, however, in recent years has suffered from the major increase in malaria in Venezuela. That country, Brazil, and Colombia accounted for 73% of all cases in the region.
According to the report, Brazil saw a "substantial reduction" in case burden in 2022, compared with 2019, with fewer than 28,000 infections. In all, the document estimated that there were 150,000 malaria cases in Brazil in 2022.
The document indicated that the number of malaria deaths in Brazil also decreased last year, with 50 deaths, compared with 58 deaths in 2021.
According to the Brazilian Ministry of Health, the Amazon is a malaria‑endemic region, recording 99% of autochthonous cases in Brazil.
Although it is the region in Brazil responsible for the highest percentage of cases, the lethality of malaria in the Amazon region is low: 0.04%. Preliminary data from the report indicate that in the country's other regions, lethality reached up to 23.25 times its 2021 rate.
"Death in these areas occurs, for the most part, in people infected with malaria coming from other countries or states in the Amazon region who do not receive prompt and adequate diagnosis and treatment due to difficulty suspecting a relatively rare disease in these areas and the lack of information travelers have of its risks," the Ministry explained.
Grounds for Optimism
Although it recognizes that the world is far from reaching the goal of a reduction in malaria case incidence and mortality rates of at least 90% by 2030, compared with a 2015 baseline, the WHO believes that the new document also brings good news.
The report cited achievements such as the phased rollout of the first WHO‑recommended malaria vaccine, RTS,S/AS01, in three African countries. A rigorous evaluation has shown a substantial reduction in severe malaria and a 13% drop in early childhood deaths from all causes in the areas where the vaccine has been administered, compared with areas where the vaccine was not introduced.
The introduction of the vaccine supplements other strategies that had already been introduced, such as nets, indoor spraying with insecticides, and other primary health interventions.
In October 2023, the WHO recommended a second safe and effective malaria vaccine, R21/Matrix‑M. The availability of two malaria vaccines is expected to increase supply and make broad‑scale deployment across Africa possible.
The WHO also congratulated countries with low disease incidence on their progress. In 2022, 34 countries reported fewer than 1000 cases of malaria, compared with just 13 countries in 2000.
This year alone, three more countries were certified by the WHO as malaria‑free — Azerbaijan, Belize, and Tajikistan — and several others are on track to eliminate the disease in the coming year.
This article was translated from the Medscape Portuguese edition.
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