1. Search in high-risk areas: Remote villages and among indigenous peoples

Yaws is sporadic with a spotty distribution. WHO suggests that researchers use purposive searches in previously endemic villages, starting with a look at historical records [8] and then a search for remote communities with historically high numbers of reported yaws.

In 2017, we started a search in Liguasan Marsh, where we had first seen yaws 22 years ago. In the second yaws study, we targeted remote villages of indigenous people. In keeping with the success of this approach, in 2021, the first confirmed yaws case in Malaysia since 1985 was a 5-year-old aboriginal child from the Batek tribe [9].

In Liberia, the 15th country designated as endemic for yaws, a different approach was used. Anecdotal reports led researchers to conduct a population-based cluster-randomized cross-sectional survey integrated with other neglected tropical diseases of the skin. This method of detection, however, required a large amount of resources and costs that most Group B countries cannot afford. Timothy and colleagues reported that during the extensive search in 1 district in Liberia, yaws was more likely to be found in remote communities [10].

Boock and colleagues [11] compared 5 methods used for yaws detection in Bankim District, Cameroon, during 2012 to 2015. The methods that yielded >70% of cases were mass outreach programs and school-based screenings in communities where yaws had been detected previously, similar to the strategy in the Philippines. Clinic-based passive detection yielded the least number of cases [11].

2. Harness local knowledge

As mentioned, in the year 2000, I identified cases of yaws by chance during a community skin survey in Liguasan Marsh, Maguindanao. Despite being a dermatologist, I did not know at the time what yaws looked like until the local health workers referred these patients to me. “Rumor” reports and rumor registries have been successfully used for yaws campaigns in endemic countries of Africa and in India [12].

3. Teach people what yaws looks like

In a country where even dermatologists and workers in the health sector in general no longer recognize yaws, information must be revived and awareness generated about the appearance of yaws, first targeting dermatologists and health personnel and then the general public in villages at high risk for yaws.

In the Philippines, the WHO’s Yaws Recognition Booklet for Communities [13] was translated into various local languages, and photographs of Filipino children with yaws were added to enable easier recognition. In 2017, our index case in Liguasan Marsh was brought in by a midwife who had seen photos during the study orientation.

In the 2017 Philippine yaws study, students were instructed to screen their household members for any skin disease with the help of flyers bearing colored images of yaws and leprosy [5]. Similarly, in Cameroon, students also were taught how to recognize yaws [11], and in Liberia, community health workers showed colored photographs of neglected tropical diseases of the skin, including yaws, to households [10].

4. Crowdsource for information on yaws

To reduce research expenses and expedite searches, I decided to crowdsource [14] information on yaws, while also conducting a review of historical records. Study staff emailed the Yaws Recognition Booklet together with a Google form questionnaire to various health professionals and invited them to participate in an online survey asking about their encounters with yaws. Through these online reports, some study sites could be selected without the expense of travel in the search for yaws.

5. Set up active surveillance

Health personnel who participated in the online survey also were asked to report any suspected yaws cases to the investigators during the study period (active surveillance). During the second yaws study in 2020, two doctors reported seeing yaws among indigenous peoples in the Luzon island group [15]. These reports may have been few in number but were considered good leads for study sites where case detection surveys would be worthwhile.

6. Use community skin health as an entry point for detecting yaws

A community skin health approach can be the most strategic approach because it raises skin health awareness generally without singling out yaws and encourages check-ups for any skin problem during school-based and community clinics. Serologic confirmation of yaws should be ensured in suspected cases. We adopted a community engagement strategy that had proved effective in detecting cases of leprosy in various parts of the country [16].

A similar integrated approach was used effectively in Liberia, prioritizing 4 neglected tropical diseases of the skin: yaws, leprosy, Buruli ulcer, and lymphatic filariasis [17].

In summary, a two-pronged approach can be used to identify yaws in a previously endemic country where it has been forgotten and status is unknown. Health researchers can start with records to select historically yaws-endemic sites that are remote, underserved, and home to indigenous peoples, interview local health workers, show photographs of yaws, and conduct case detection with skin and serologic screening on children and others with suspected yaws. Simultaneously, crowdsourcing can be conducted to gain information from health personnel nationwide using online methods to raise awareness, educate about yaws skin and bone signs, and request reports or records. This approach also initiates an informal active surveillance that enables health personnel to report suspected yaws cases via teledermatology. If suspected yaws is reported, resources can be focused on the identified village for case detection activities (Fig 2).

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Fig 2.

Two-pronged approach to find yaws in a previously endemic country: (1) start with historical records to find yaws-endemic sites and (2) crowdsourcing from health personnel online; show yaws skin signs and ask for any reports or records. (Created with BioRender.com). b. Aeta village, Tagkawayan, Quezon*; c. Flyer of yaws and leprosy photos used during the yaws studies**; NTD Neglected Tropical Diseases; d. Skin examination by dermatologist Dr Belen Dofitas (Sultan Kudarat) 2017*; e. DPP kit*; f. Online survey form used during yaws studies*; g. Cover of Yaws Recognition Booklet for Communities (Filipino version)**; h. Yaws image on a cellphone* *Photo credit Dr. Belen L Dofitas; ** Yaws Recognition Booklet for Communities (Filipino version).

https://doi.org/10.1371/journal.pntd.0011515.g002