Today I've been trying to get my head round the government's #COVID19 quarantine policy. Which is challenging because there is no clear rule on why some countries get exempted from quarantine and others don't. For instance:

Here are the latest case rates per 100k in Vietnam, Germany & Hong Kong. All three have been in the news recently warning of localised rises in #COVID19 cases. But as you can see, Vietnamese rates are still v low. The German curve still looks contained but HK looks quite scary

All three of these countries are included in the UK's exemption list, so you don't have to self-isolate/quarantine when you come back from them. Yet Hong Kong is clearly battling a serious outbreak. Why hasn't it been dropped from the list? https://www.gov.uk/guidance/coronavirus-covid-19-travel-corridors

There's no simple answer but perhaps it's because while the trajectory looks scary the LEVEL of infection in HK is still low compared to many European countries. Above the UK here but below Austria or Switzerland. Still: have you noticed something else that sticks out here?

In the Bahamas the infection rate is far, far above what you see in Hong Kong, or for that matter Spain. Similar story in Luxembourg (though some might argue that its small population makes that number a bit suspect). So: does this mean they might be added to the quarantine list?

In short: dunno. No-one knows because govt has been incredibly vague abt how it makes these decisions. Though they have hinted that it's a function not just of infection rate and trajectory but how many people from the UK go there. LOADS of ppl go to Spain. Not so many to Bahamas

Multiply infection rates by visits and you get a (pretty unscientific) measure I'm calling the #COVID19 tourism risk index. Bahamas goes from top to bottom. Sweden interestingly is smack bang in the middle (yet it's on the quarantine list, so the index doesn't explain everything)

Further up the list, things get interesting. Spain's sky-high tourism numbers mean its only moderately high infection rate becomes a serious problem. And look at France: low infection rate but consider flow of people and it's above Portugal in the index...

The index explains some of what govt has done but not everything. Why impose regional bans on some (eg Portugal, where the FCO says it's safe to go to the Azores but not to the mainland) but national bans on others (in Spain infection rates on the islands are lower than UK?)

Govt is clearly right to act fast to prevent a 2nd wave of infections in UK but by being so vague and inconsistent it risks putting people off travelling altogether. Quarantine rules will have more success if they are respected. Clarity abt how they work will help build respect.