Confirmation of a new coronavirus has hit world markets, hurting travel companies but boosting makers of face masks and other medical equipment.
Six people have died from the virus, which has no cure, with more than 290 cases confirmed in China, Thailand, Japan and South Korea.
China, where most of the victims are, has also confirmed the first person-to-person transmission of the virus.
The Shanghai Composite Index lost more than 1.4%, hitting its lowest point this year, while its currency fell from six-month highs.
China Eastern Airlines lost 2.9% but Shanghai Dragon Medical, which makes medical disposable and healthcare products, and Tianjin Teda, a conglomerate whose products include medicines, were both up by 10%.
The Chinese government says the virus belongs to the same family of coronaviruses that causes Severe Acute Respiratory Syndrome (SARS), news that prompted a number of airports around the world to announce they would temperature screen passengers.
The SARS outbreak in 2002-03 started in China and killed nearly 800 people around the world.
In Japan, the Nikkei share average fell 0.91% after reaching a 15-month high on Monday, with ANA Holdings losing 2.2% and Japan Airlines dropping 3%. Japan Airport Terminal, which operates Tokyo's Haneda Airport, fell 4.5%.
Meanwhile, Azearth, which supplies protective clothing, jumped 16.2%; Airtech Japan, which makes air showers and other air-purifying products, gained 8%. Shikibo, which produces anti-virus masks, was up 10.8%.
In Hong Kong, the Hang Seng Index lost 2.7%, with shares in airlines, cinemas and casino operators falling but shares in pharmaceutical companies gaining.
Alex Wong, managing director at Ample Finance in Hong Kong, said: "It is all about the fear.
"The selling originated in travel-related stocks and is now spreading out. The ultimate fear is that this may spread with the tremendous human flow during the (Chinese Lunar New Year) holiday."
Margaret Yang, an analyst at brokerage CMC Markets in Singapore, said: "The sell-off is just the beginning, we will see more in days to come."
In China, however, some analysts were playing down virus fears.
Zhang Qi, a Shanghai-based analyst at Haitong Securities, said: "We have more experience in dealing with diseases.
"We will need to watch whether it spreads further, but so far the scale is not that big."
Markets in South Korea, Australia and India were also down, with Rajiv Biswas, Asia Pacific chief economist for IHS Markit, saying the virus was "developing into a major potential economic risk to the Asia-Pacific region now that there is medical evidence of human-to-human transmission.
He added: "Since the 2003 SARS crisis, China's international tourism has boomed, so the risks of a global SARS-like virus epidemic spreading globally have become even more severe."
In London, the FTSE 100 was heading for its worst day since early December, shedding more than 1% as virus fears hit luxury and travel stocks.
Asia-exposed Burberry lost 3.3%, British Airways owner IAG lost 2.3% and InterContinental Hotels fell 1.7%.
Markets.com analyst Neil Wilson said: "We don't know how bad this will be, but with authorities confirming the disease can spread between humans, it's wise to be on guard for this outbreak to get worse before it gets better."
The pan-European STOXX 600 lost 0.7% with Air France down 1.8% and Lufthansa down 2.1%.
Luxury brands that are focused on China's consumers were also hit: LVMH (Moet Hennessy - Louis Vuitton) was down 2.7%, Kering was down 3.8% and Hermes lost 2.2%.