But then I thought the psychological consequences for a not inconsiderable amount of people would be disastrous, as it seems to my girlfriend. [...] I don't want to be a information hazard source.
It's important to note that unpleasant emotions are functional when faced with a new threat that one hasn't prepared for; the whole point of emotions like fear is to reorient ourselves towards the reality we find ourselves in and come up with a more informed (and therefore hopefully more effective) response. It is always unpleasant to realize that things aren't quite as nice as we've been hoping and planning on, but the actual information hazard would be things that "protect" people from the emotion that could have protected their life and well being as well as the life and well being of their loved ones. What you're talking about doing is the opposite of an information hazard.
That said, there are a few things that can be important for doing it right.
One is that you want to draw very clear boundaries between the position you advocate and alarmism. You're pushing for integration of scary information as well, not for blindness to good news and the potential for optimism. You don't want to push people from "white thinking" to "black thinking", you want to encourage people to take in all information and pick the most appropriate shade of gray given the current information available.
Not only is some shade of gray more accurate than pure black, making this distinction clear will help you persuade people. When people are primed and ready to "not give into alarmist/doomer thinking", you don't want them to pattern match you as this opposite form of irrational thought. If you have had/seen any conversations about this where people are saying "it's not the end of the world" in response to statements like "it's not 'just the flu'", this is what is going on. You're seeing them argue against what they don't want to believe rather than what is being argued. I would make sure to include and emphasize everything optimistic you can without sacrificing accuracy, and make sure you're not trying to "push one side" as much as offer more information as someone who can see both the reassuring and the scary.
Secondly, recognize the fact that you are deliberately exposing people to scary ideas which many many people are not emotionally prepared to deal with. The whole reason people dismiss reasonable arguments as "alarmist" is because their emotional response would be somewhat like your girlfriend's, and they don't want to have to face that. To every extent you can, ease this transition. Be comforting and hospitable, even if just in body language or vocal tone in a YouTube video. You want to emphasize (explicitly or implicitly) that feeling fear is not a sign of cowardice but of courage -- after all, they've proven themselves capable of avoiding it if they wanted to. You want to give people an idea of what they can do, and what their cues should be for various decisions. This can help lower the amount of uncertainty that they will have to deal with and make the transition more comfortable, as well as cutting down on the unnecessarily duplicated cognitive effort of "figuring out what the hell to do about it". People are always free to doubt and question and to disagree, of course, but it can be nice having a "default" value to jump to so that you can update on risks without having to be emotionally and mentally ready to compute all your own ideas on first principles.
This is very important work, as there are relatively few people who are willing and able to engage with the scarier possibilities without losing touch of hope and succumbing to alarmist paranoia and losing all credibility. I definitely encourage you to make the video.
After spending 3 days reading all of Lesswrong's posts and comments (and sources cited) related to coronavirus, I started taking action (summarizing the information collected and planning the least harmful ways to alert my closest peers to start preparing - we only have two confirmed cases still in Brazil). In my entire network of friends, I have not yet seen a single person who even takes the matter seriously. When I show a small amount of data (2~5 minutes of reading) and its extrapolations for the next weeks/months, the natural reaction is "you are forgetting a lot, someone will invent a cure/vaccine, there is nothing to worry about". They don't care about the smoke.
However, by showing a reasonable amount of data (1 hour reading) about coronavirus around the planet to my girlfriend and its long-term consequences (up to a year), she was convinced that it was a pandemic, that the consequences would be very bad, and her reaction was to cry. I showed an amount of data equivalent to 30 minute reading for my closest friend, his reaction was "tell me what you gonna do and when you gonna do, I'll do the same"
As there are a reasonable amount of people who don't think the subject is relevant or even know anything about it, I'm creating a video for YouTube in Portuguese. But then I thought the psychological consequences for a not inconsiderable amount of people would be disastrous, as it seems to my girlfriend. However, I see a lot of valuable information that I can only find on Lesswrong and no other source in Portuguese and it seems it would be a mistake not to share. At the same time, I don't want to be a information hazard source.
On one hand, I can simply create the video, translate it to English and share with Lesswrong community to see if the community approves.
On the other hand, you could say what you think it would be an adequate sequence to explain the subject, like: [what is coronavirus > why you should pay more than 1 minute attention to it > current number of deaths vs expected number of deaths > who is probably going to die > you have permission to be worried and take precautions > what are the precautions > what data should trigger behavior changing for more aggressive precautions > etc]