Just glanced at the Abstract, but don't they say the opposite?
Maybe it's shed in ways not very contagious? (they mention stool)
The 2% or lower figure is based on a lot of data from a lot of countries, and the growing belief that maybe roughly half of all positives show no symptoms.
Wrt places like India and Indonesia: I think it's somewhat a matter of chance. Even in Hubei, with the highest concentration of cases in the world, only a little more than 1 in a thousand have been infected--and the large majority of those now are recovered or have died. So when people from China--or now S. Korea, Italy, etc--travel to another country, it's somewhat of a crapshoot whether an infected person is in that group, and if so, whether s/he spreads the virus to the point where community takes over. The Philippines had the first death outside of China, a Chinese man, but only his partner and one other person tested positive, and both recovered. This was several weeks ago, so there could have been no community spread. Now cases are popping up in the Philippines. Some positive foreigner or foreigners must have arrived, and this time community took over. I think there's a lot of chance in that.
The Philippines, by the way, will be a test case of temperature and humidity, since both are always high there. Also, UV light should be less of a factor, because in the tropics, daylight hours are close to constant all year round. But longer daylight hours could be a factor in those many countries in more temperate zones.
But the most puzzling, and potentially valuable, situation seems to be in Japan. The virus is still spreading, but continues to do so far more slowly than in most othercountries where it has been firmly established. Why? Whatever Japan is doing, we need to bottle it.
Among unintended consequences, one thing that seems obvious to me, at least in countries that haven't yet locked down, is more driving of cars. For example, in the Bay area, where I live, many people generally commute by BART, the subway. During rush hours, cars are usually packed with people. I can't imagine a more favorable environment for spreading the virus. I've railed against cars for decades, but in this situation, I can't blame anyone for driving one, if they can't work at home and they live too far to bike. I think people will even be reluctant to use the many busses, vans and carpools available. Public transportation, after all the efforts made to encourage it, is now a great danger.