LONDON - Surveyors were taken hostage in Yemen, accused of being representatives of Dracula in Papua New Guinea, worked in sandstorms and temperatures of 50 degrees Celsius in Ethiopia.
It was all part of the day's work for some of the thousands of people who have completed what the organizers say is the largest ever survey of an infectious disease, examining 2.6 million people in 29 countries for the eye infection trachoma.
"They faced tribal warfare and rogue villagers in Papua New Guinea who spread a rumor that the teams were vampires," said Anthony Solomon, chief scientist of the Global Trachoma Mapping Project (GTMP).
"They worked in Ethiopia's Afar region, one of the most hostile territories in the world in which to conduct community-based research, amid sandstorms, temperatures of 50 degrees Celsius and deadly venomous spiders," he added.
The scale and quality of the survey mean trachoma, an extremely painful disease which causes blindness, could be eliminated by 2020, according to the GTMP organizers - the World Health Organization, the Carter Center, and the international NGO Sightsavers.
"We know where it is, we know how prevalent it is, so we know what to do," said Tom Millar, who co-led the project. "We're very hopeful it can now be eliminated."
Trachoma is one of 17 so-called neglected tropical diseases earmarked by the WHO to be controlled, eliminated or eradicated by 2020.
It has partly or completely blinded at least 1.8 million people, and affects some of the poorest and most marginalized rural communities, the WHO says.
"In countries like Ethiopia (prevalence) is mind-numbingly, shockingly high - in some communities over 50 percent of the population have trachoma," said Millar, who is neglected tropical diseases operations director at Sightsavers.
Before the survey began in 2012, only one region in Ethiopia had received support for tackling the disease. "They did not know what to do. They were just looking into a black hole.
"Now they've mapped the whole country and they almost have funding and support to deliver all the interventions for the country," Millar said.
"They are now talking about when they eliminate trachoma."
EYES SCRAPED BLIND
The disease is spread through contact with infected clothing, hands or flies, and affects communities with little access to clean water and sanitation.
Repeated infections make a person's eyelashes turn inwards, so that they scrape the surface of the eyes with every blink.
"It's a hugely painful way to go blind," Millar said.
More than 550 teams of health ministry staff in the countries surveyed were trained to spot the disease and use smartphones with GPS systems to record the data. They also recorded water and sanitation levels.
Trachoma rates were lower than expected in some countries including Nigeria, Laos, Cambodia and Egypt.
"A lot of that is because, since this was first looked at in the 1980s and 1990s, there's been a lot of social and economic development ... that has helped reduce the spread of the disease," Millar said.
Not everywhere could be mapped. Eighteen countries had districts where it was too dangerous, including Borno and Adamawa states in northeastern Nigeria which had to be left out because of the militant Islamist group, Boko Haram.
Quite large areas in Ethiopia's Somali Region could not be mapped because of not safe to go there.
"Without mapping we cannot launch interventions," said Solomon, who is medical officer for trachoma at WHO.
"But I think that's ok. If there are bullets in the air the biggest health problem is not the risk of blindness in 20 or 30 years' time, it's something much more visceral and immediate," he added.
COUNTRIES SUPPORT EACH OTHER
As well as gathering quality data, the survey has helped develop strong ties between countries where the disease is endemic.
"We now have a lot of countries officially supporting each other, and need very little in the way of external support. It's very important for ... trachoma elimination in a lot of these countries," Solomon said.
To eliminate trachoma, people living in areas with high levels of the disease need up to five years of antibiotic treatment, given once a year.
Between 1987 and 2012, about 1,100 districts in the countries at risk were mapped, leaving a further 1,200 districts that were suspected of having trachoma.
"In 2012 everybody realized that the biggest hurdle to elimination was the fact that we only had about 50 percent of the data required," said Millar.
So Solomon and Millar spent months gathering experts to help work out the best way to gather reliable data at speed and on a massive scale.
"It felt like pushing boulders up hills at the beginning, but once you got it to the top it was fantastic, and we struggled to hold onto it on the way down the hill as the momentum has taken over," Millar said.
"The challenge now is: how does it encourage new funders to the table to make sure that we get over the line and do eliminate by 2020," he added.
The quality of the survey's data means many districts have already been enrolled to receive free antibiotics donated by Pfizer pharmaceutical company through the International Trachoma Initiative.
"If you're going to make an impact you've got to have the detailed information ... and I don't see anything that's better than this (survey)," said David Molyneux, professor at the Liverpool School of Tropical Medicine.
Molyneux led a team of scientists that crisscrossed Nigeria checking for guinea worm, declaring the country free of the disease in 2013. He was also involved in a campaign to eliminate river blindness in West Africa.
The app developed for the trachoma survey is also being trialled for gathering information about other diseases on WHO's list, including schistosomiasis, yaws, soil-transmitted helminth infections and guinea worm disease.