Galah

Total cases have now passed 1500 (currently 1514) and getting up to 1650 would require a massive outbreak over the next week.

Updating my prior forecast. As of 9/13/25, the CDC is reporting 1,490 cases of measles in 2025 (note that I am not using in-progress weeks, I don't find them useful due to lags in reporting). I updated my scenarios as follows with the latest data. Given these figures, the only plausible scenario is the 1500-1649 category:

- If cases match what was observed in the same weeks last year, there would be 5 new cases = 1,495 total - just under the threshold, but not really a plausible scenario anymore as we haven't seen numbers this low all year.

- If cases remain at the weekly average they have shown in recent weeks (20.5), there would be 50 new cases = 1,540 total

- If cases remain elevated 6.16x higher than they were in Jan-early August 2024, there would be 31 new cases = 1,520 total

Thinking about this another way: it will take 10 cases in 2.5 weeks to reach the cutoff of 1,500 total cases, and this comes out to ~4 cases per week. So far, this has occurred in 34 weeks of 2025 and 29 weeks of 2024 - a total of 71% of weeks since January 2024 and nearly every week this year. This indicates almost certain likelihood of reaching 1,500 cases.

I think the final total almost certainly be over 1,500 so I'm dropping the lower category, and will eliminate it entirely as soon as it's out of contention (this could easily happen next week).

Further adjusting this forecast because @ctsats highlighted just how pervasive the undercounting/lag issue is in this report. That means it's even more likely that the 1500 threshold will be met. See my forecast from earlier today for more details.

Updating my prior forecast. As of 8/30/25, the CDC is reporting 1,429 cases of measles in 2025 (note that I am not using in-progress weeks, I don't find them useful due to lags in reporting). I updated my scenarios as follows with the latest data. Given these figures, the only plausible scenarios appear to be the 1350-1499 and 1500-1649 categories:

- If cases match what was observed in the same weeks last year, there would be 18 new cases = 1,447 total.

- If cases remain at the weekly average they have shown in recent weeks (19), there would be 84 new cases = 1,513 total

- If cases remain elevated 6.16x higher than they were in Jan-early August 2024, there would be 111 new cases = 1,540 total

Thinking about this another way: it will take 71 cases in 4.5 weeks to reach the cutoff of 1,500 total cases, and this comes out to ~11 cases per week. So far, this has occurred in 32 weeks of 2025 and 7 weeks of 2024 - a total of 45% of weeks since January 2024 and nearly every week this year. This indicates decent likelihood of reaching 1,500 cases without another major outbreak.

I think the final total will be quite close to 1,500 so I'm splitting probabilities across the two categories, slightly favoring the lower category in keeping with my earlier forecasts and the crowd forecast.

Updating my prior forecast. As of 9/6/25, the CDC is reporting 1,451 cases of measles in 2025 (note that I am not using in-progress weeks, I don't find them useful due to lags in reporting). I updated my scenarios as follows with the latest data. Given these figures, the only plausible scenarios remain the 1350-1499 and 1500-1649 categories:

- If cases match what was observed in the same weeks last year, there would be 8 new cases = 1,459 total.

- If cases remain at the weekly average they have shown in recent weeks (19), there would be 71 new cases = 1,521 total

- If cases remain elevated 6.16x higher than they were in Jan-early August 2024, there would be 49 new cases = 1,500 total

Thinking about this another way: it will take 49 cases in 3.5 weeks to reach the cutoff of 1,500 total cases, and this comes out to ~14 cases per week. So far, this has occurred in 28 weeks of 2025 and 2 weeks of 2024 - a total of 34% of weeks since January 2024 and nearly every week this year. This indicates decent likelihood of reaching 1,500 cases without another major outbreak.

I think the final total will be quite close to 1,500 so I'm splitting probabilities across the two categories, slightly favoring the higher category - my forecasts have trended in that direction for several weeks now, and it is in keeping with the crowd forecasting trends.

Updating because more time has passed without a major hurricane making landfall. We are now well into September and would need two major hurricanes to make landfall before any options besides 0-1 apply. In the past three years, there has been one major hurricane across the August-September period each year, so having two just in September would be unexpected. I'm going to consider it effectively impossible at this point but will reconsider if a hurricane occurs soon.

No indicators that this is likely to happen, and crowd forecast keeps trending toward zero