Seeing mountain gorillas in their natural habitat is undoubtedly top of many people's bucket list, however, scientists have warned adventurous travellers may unwittingly spread infections like the coronavirus if they get too close.
England's lockdown and similarly strict restrictions throughout the rest of the UK make it illegal to go abroad for non-essential trips.
Nevertheless, scientists from Oxford Brookes University are concerned infected tourists may leave gorillas vulnerable in the future, with selfies being to blame.
After analysing nearly 1,000 Instagram posts, the team concluded most gorilla-trekking tourists get too close to the animals, potentially putting the great apes at risk of severe diseases.
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In October 2020, scientists from University College London reported 26 animals – including gorillas – that are "regularly in contact with people" around the world have the potential to catch the coronavirus.
This was borne out in January 2021 when gorillas at San Diego Zoo tested positive for the infection.
"The risk of disease transmission between visitors and gorillas is very concerning," said lead author Gaspard Van Hamme.
"It is vital we strengthen and enforce tour regulations to ensure gorilla-trekking practices do not further threaten these already imperiled great apes."
Previous research suggests "respiratory illnesses represent the main threat posed by tourists to great apes", with the risk rising alongside "increasing proximity between the two", the Oxford Brookes scientists wrote in the journal People and Nature.
Humans may be capable of transmitting viruses like mumps and measles, food poisoning bacteria such as E.coli and even the parasitic mite that leads to scabies to gorillas.
"In addition, the novel coronavirus SARS‐CoV‐2, which can cause COVID‐19 [the disease brought about by the infection] in humans and is responsible for the 2019–2021 pandemic, is known to also to infect great apes," wrote the scientists.
Gorilla treks provide a "substantial source of revenue for the conservation of this threatened primate and its habitat".
Nevertheless, the threat of human-to-gorilla disease transmission could be "disastrous".
To better understand the extent of the risk, the scientists analysed 858 photographs posted on Instagram between 2013 and 2019.
The coronavirus was formally identified on 31 December 2019, however, research increasingly suggests the infection may have been circulating for a considerable time towards the end of that year.
The Instagram photographs were taken in the gorillas' native East African habitats in the Democratic Republic of Congo (DRC), Uganda and Rwanda.
Watch: Gorillas test positive for coronavirus at San Diego zoo
Results of the analysis reveal 85% of the photographed tourists got within a "critical" 4m (13.1ft) distance of the gorillas, with just 3% staying the recommended 7m (22.9ft) away.
The minimum 7m recommendation is based on research suggesting "disease-carrying droplets" can travel up to 6m (19.6ft).
The scientists also recorded 25 cases of "physical contact" between a tourist and a gorilla.
Face mask use was investigated, however, it was only able to be recorded in the DRC, where 65% of those photographed donned the protective covering.
"In the photos we analysed, we found face masks were rarely worn by tourists visiting gorillas, and that brings potential for disease transmission between people and the gorillas they visit," said co-author Dr Magdalena Svensson.
"With people all over the world getting more used to wearing face masks we have hope in the future wearing face masks will become common practice in gorilla trekking."
Tourists have apparently become more brazen over time, with the distance between the average adventurer and gorilla decreasing by around 1m (3.2ft) between 2013 and 2019.
"Immature" gorillas mingled closer to humans than their adult counterparts, the results show. This was particularly true when the tourist was female.
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"This research provides a valuable perspective on how much tourists are willing to share their too close encounters with mountain gorillas through Instagram, which creates expectations for future tourists," said Dr Gladys Kalema-Zikusoka from Conservation Through Public Health in Uganda.
"It highlights a great need for responsible tourism to provide adequate protection while minimising disease transmission, especially now during the COVID-19 pandemic."
Russell Mittermeier from the Primate Specialist Group added: "It has become apparent in the past few years that studies of anthroponotic [originating in human activity] and zoonotic [when an infection jumps from an animal into a human] disease spread are crucial to the field of primate conservation.
"With that in mind, it is very exciting to see the new research on this topic coming out of the Primate Conservation Group at Oxford Brookes University.
"While this study focused on one species, the mountain gorilla, the lessons learned are also applicable to many other primate species that are increasingly coming into contact with people."
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