Illumina (ILMN) was hit with two large downside gaps this year. These hard body blows have taken their toll on the daily and the weekly charts. This could be a "requiem" for this bio tech name.
In this daily chart if ILMN, below, we can see the gap down in April with the big visible surge in volume -- pretty intense selling for a couple of days. Prices stabilized in the $135-$130 area for a few months and managed to make a fairly good recovery to a new high but then another big downside gap and volume surge. ILMN held again around $135 but have since slipped lower this month. Prices are below the declining 50-day and 200-day moving averages.
The On-Balance-Volume (OBV) line has been declining all year and has made a new low along with prices. There is a bullish divergence between the lower lows in October and December and higher momentum readings, but I do not expect that it will translate into an upside move.
This weekly chart of ILMN, below, going back to 2013, shows a large top formation going back to 2014. The decline in December has broke the lows of 2014, 2015 and, we already know, earlier in 2016. Prices are below the declining 40-week moving average line. The weekly OBV is not going in the right direction in that it rose for much of 2016 and only turned down in the past two months.
The Moving Average Convergence Divergence (MACD) oscillator is below the zero line for a sell signal.

Bottom line: Considering the major top formation on ILMN's weekly chart, I would not try to get in the way of the bears. It would take a rally above $140 to turn the chart to neutral.