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* Facebook slides on warning of slowing revenue growth
* Tesla jumps after posting second straight quarterly profit
* Dow down 0.35%, S&P 500 down 0.43%, Nasdaq down 0.41% (Updates to mid-afternoon, changes byline)
By Chuck Mikolajczak
NEW YORK, Jan 30 (Reuters) - U.S. stocks dropped on Thursday as the coronavirus outbreak raised concerns about damage to the global economy, with what is shaping up to be a lackluster earnings season contributing to the decline.
Shares of the social media giant slumped 5.82% after the company warned of slowing growth as its business matured and it reported a surge in quarterly expenses.
The decline weighed on the S&P communication services index , which lost 1.36%. Defensive sectors such as utilities and consumer staples, considered safer in times of economic uncertainties, posted modest gains.
The main U.S. stock indexes are on course for their second straight week of declines as the virus has disrupted global travel and forced several companies to suspend operations in China.
The World Health Organization's Emergency Committee is due to reconvene on Thursday to decide whether to declare the virus, which has killed 170 in China and infected 8,100 people worldwide, a global emergency.
The Centers for Disease Control and Prevention reported the first U.S. incident of person-to-person spread of the virus.
"The question in this case is after it runs its course than what are you left with?" said Willie Delwiche, investment strategist at Robert W. Baird in Milwaukee.
"You are left with yields that have moved lower, earnings that are struggling to deliver and an increasingly widespread view the Fed is going to have to come in and cut rates again this year."
The Dow Jones Industrial Average fell 99.17 points, or 0.35%, to 28,635.28, the S&P 500 lost 14.14 points, or 0.43%, to 3,259.26 and the Nasdaq Composite dropped 38.07 points, or 0.41%, to 9,237.09.
Earnings expectations have been slowly improving for S&P 500 companies, with Refinitiv data showing a 0.7% rise in fourth-quarter profit, compared with a 0.6% decline estimated at the start of the season. But the growth remains modest with the S&P 500 roughly 2% off its record high.
Microsoft Corp gained 2.31% after it beat expectations for quarterly earnings, driven by Azure cloud computing revenue growth.
Tesla Inc jumped 11.01% after the maker of electric cars posted a second straight quarterly profit as vehicle deliveries hit a record.
Altria Inc slid 5.50% after the tobacco company said it took another $4 billion charge on its investment in Juul Labs Inc. Package delivery firm United Parcel Service Inc dropped 6.37% after it forecast full-year earnings below estimates.
Declining issues outnumbered advancing ones on the NYSE by a 2.04-to-1 ratio; on Nasdaq, a 2.23-to-1 ratio favored decliners.
The S&P 500 posted 37 new 52-week highs and 14 new lows; the Nasdaq Composite recorded 42 new highs and 91 new lows. (Reporting by Chuck Mikolajczak Editing by Nick Zieminski)