Research results indicate cholera outbreak in Malawi might have possibly been imported by a traveller from Pakistan

* Last cholera situation report of August 7, 2023 indicated the outbreak has been controlled in 27 Health districts

* In past 14 days of August 7, the disease was reported in only two districts of Chiwakwa and Mangochi

By Duncan Mlanjira

A group of researchers have published a paper that presents “strong evidence” that the strain of the bacteria that causes cholera which led to the disease’s outbreak in the country from early 2022-2023 was new to Malawi and is the same strain that circulated during Pakistan’s floods some 3,800 miles away.

The researchers are 32 of them with several Malawi nationals — Lucious Chabuka, Wonderful T. Choga, Carla N. Mavian, Monika Moir, Houriiyah Tegally, Eduan Wilkinson, Yeshnee Naidoo, Rhys Inward, Christian Morgenstern, Samir Bhatt, G. R. WilliamWint, Kamran Khan, Isaac I. Bogoch, Moritz U.G. Kraemer, Cheryl Baxter, Massimiliano Tagliamonte, Marco Salemi, Richard Lessells, Collins Mitambo, Ronald Chitatanga, Joseph Bitilinyu- Bango, Mabvuto Chiwaula, Yollamu Chavula, Mphatso Bukhu, Happy Manda, Moses Chitenje, Innocent Malolo, Alex Mwanyongo, Dr Bernard Mvula, Dr Mirrium Nyenje, Tulio de Oliveira and Dr Mathew Kagoli.

They conclude that it’s possible an airplane traveler carried the bacteria from Pakistan to Malawi as the two countries are closely linked by a high frequency of air traffic and its passengers.

The report’s abstract says since early 2022, in the aftermath of two extreme weather events, Malawi experienced its largest ever cholera outbreak, with over 58,000 reported cases and 1,761 deaths as of May 2023.

“We generated 49 high-quality, near-complete Vibrio cholerae genomes in Malawi from isolates collected between December 2022 and March 2023 from all three regions of Malawi.

“Using phylogenetic methods with 2,159 publicly available genomes, we present evidence suggesting that the Malawi outbreak strains originated from the Pakistan outbreak, the estimated most recent ancestor of this lineage, named T15, was during the Pakistan floods, and once introduced into Malawi was exacerbated by major floods between June and October 2022.

“The extreme weather events and humanitarian crises in Malawi provided the environment for the spread of Vibrio cholerae, and the subsequent movement of large numbers of people may have facilitated its spread to susceptible populations in areas relatively unaffected by cholera for over a decade.

However, there is a disclaimer, saying saying the report is “a preprint and has not been peer-reviewed” — meaning: “It reports new medical research that has yet to be evaluated and so should not be used to guide clinical practice.”

But they conclude that their genomic analysis provides strong evidence of a link between the large cholera outbreaks in Pakistan and Malawi, consistent with prior genomic analyses revealing the importance of long-range V. cholerae transmission events between Asia and Africa.

“Our main findings agree with another recent analysis of the Malawi outbreak, and with a genomic analysis of six cases from South Africa in 2023 (three of which were epidemiologically linked to Malawi).

“The extreme weather events and humanitarian crises in Malawi provided the environment for the spread of V. cholerae, and the subsequent movement of large numbers of people may have facilitated its spread to susceptible populations in areas relatively unaffected by cholera for over a decade.

“The relatively narrow sampling date range for this genomic analysis means that we cannot confidently differentiate whether the introduction of V. cholerae was responsible for initiating the outbreak, or if it just contributed to the later expansion of the outbreak.

“Additional sequencing of isolates from earlier in the outbreak may help to clarify this,” say the researchers, while also indicating that they are also working with partners in other heavily affected African countries to conduct genomic sequencing of V. choleraeisolates, “which will help with understanding the extent of cross- border regional transmission at different phases of the outbreak”.

“Overall, this highlights the need for coordinated global and regional cholera prevention and control efforts, and the importance of heightened awareness, data sharing and preparedness whenever outbreaks are occurring in any part of the world.”

Meanwhile, the last situation report from Ministry of Health was on August 7, 2023 that indicated that the outbreak has been controlled in 27 Health districts — adding that in past 14 days of August 7, the disease was reported in only two districts of Chiwakwa and Mangochi.

The cumulative confirmed cases reported since the onset of the outbreak was at 58,981 accompanied by 1,768 related deaths while the cumulative and epidemiology Week 30 case fatality rates were 3.0% for new cases and 13.3% for deaths.

A total of 57,213 people have recovered and that no case was in the treatment centres and since the onset of the outbreak, Lilongwe has ranks highly with most cases at 12,778 cases and 599 deaths — followed by Blantyre (8,932 case/227 deaths).

Mangochi is at 8,512/124; Balaka (4,415/103); Salima (3,622/99); Machinga (2,439/86); Dedza (2,164/82); Nkhata Bay (1,517/44); Nkhotakota (1,469/58); Chiradzulu (1,425/45); Ntcheu (1,372/50); Dowa (1,344/40); Thyolo (1,206/34) and Rumphi (1,051/17).

Health Minister Khumbize Kandodo Chiponda said 26 out of 28 districts had not reported new cases in the past 14 days of August 7 but expressed concerns that some sections of the society “do not understand the importance of following the recommended cholera preventive and management measures”.

“The aim of these measures is to reduce the further spread of the disease,” she said. “As a Ministry, we will continue to make sure our health workers continue to provide the right information to every on the recommended preventive and management measures.

“Let me encourage our esteemed traditional, political and religious leaders to continue engaging communities they serve on this highly important matter. Together we will win this fight against cholera.”

The full Malawi cholera research publication is available on: https://www.medrxiv.org/content/10.1101/2023.08.22.23294324v1.full