Let's look at this Paper for a bit.

This report is about some pills made in the US where a mistake were made and they were way too strong:

"The supplement was distributed by Company A, a small privately owned company in Atlanta, Georgia. The product had been on the market for 12 years without any reported problems. Company A received the finished product from a manufacturer in Arkansas, which in turn received ingredients from suppliers in Louisiana. The FDA conducted inspections of the manufacturing and supply plants after the outbreak was identified. Company A had recently changed the manufacturer of the product, and the misformulated lots were the first lots produced after the change. Employee error at one of the ingredient suppliers was determined to be the cause of the increased selenium in the product."

"Initial serum selenium concentrations ranged from 321 to 1500 μg/L, with a mean of 761 μg/L and a median of 664 μg/L; 3 were higher than 1000 μg/L (reference mean, 125 μg/L).12"

You're aiming for 97 μg/L.These were up to 15X too high.

In all of history exactly zero people have died from too many vitamins. Imagine a 10X morphine overdose. 30,000 - 90,000 people a year die from pharmaceutical products.

"Selenium is a naturally occurring mineral required for good health. It is obtained from food, and the recommended dietary allowance is 55 μg/d for persons 14 years or older, with a tolerable upper intake limit of 400 μg/d.1,2"

So "150" is right out, they say 400. Now this is silly. An 100 pound 18 year old male and a 50 pound 60 year old chain smoking female do not have the same requirements. Any time you see a single hard number you can rest assured it's wrong. The target is 97 micrograms per litre of plasma. In an person of average size and age in perfect health this is about 200mcg a day.

Abram Hoffer who invented this type of medicine took 600 mcg a day. As we age we need more. He was 93 when he died (of stroke)

"Symptoms of selenium toxicity include nausea; vomiting; nail discoloration, brittleness, and loss; hair loss; fatigue; irritability; and foul breath odor (often described as “garlic breath”).1,2,4–6"

You can't call these serious. You sure won't be catching any virus though! Just take less for a bit if your stomach hurts and you smell like garlic.

"The serum selenium concentrations reported during this outbreak are high for subjects ingesting inorganic forms of selenium. Ingestion of organic selenium in the form of Selenomethionine is associated with much higher serum selenium concentrations than ingestion of inorganic forms.1"

Don't take inorganic forms (ie, Sodium selenite) if you're worried. Your body can handle much larger doses in organic forms (Selenomethionine, Selenocysteine, Brazil or Gabon nuts)

"Outbreaks of selenium poisoning are rare; the last occurred in 1983 and involved 12 persons who had consumed inappropriately potent selenium tablets as a dietary supplement.7,8 "

So don't take 20,000 mcg a day from pills made in error. Notice, nobody died from this, ever.

"This episode of selenium toxicity caused by a misformulated commercially distributed dietary supplement presented unique clinical and public health challenges. Given the rarity of selenium toxicity, along with the array of nonspecific symptoms, recognizing the diagnosis can be difficult. Furthermore, a substantial proportion of patients had not yet sought medical attention at the time they were contacted by public health investigators."

It's rare, happens when pill companies make a mistake, and not serious enough to warrant going to the doctor. Of course, this can't happen with Brazil (or Gabon) nuts.What this really proves is even with a 15X overdose no great harm occurs. Don't try this with sleeping pills or pain killers!