Earlier, the domestic currency traded as low as 62.81 US cents, its lowest level since mid-October.
California officials said the person infected lives in Solano County, northeast of San Francisco and is getting medical care in Sacramento Country but didn't release further details.
Hamish Pepper, fixed income and currency strategist at Harbour Asset Management, said that although US President Donald Trump's comments at a press conference on his return from India appeared designed to calm financial markets, "the market latched onto the more worrying aspects."
Trump said the US is "very, very ready" to face the virus threat and that Vice President Mike Pence will be in charge of the American response.
Trump said the spreading of the disease through the US isn't inevitable. He said the US might have to restrict travel to Italy, South Korea and other countries as a result of the virus, but now was not the right time.
Pepper said US equity futures are down more than 1 per cent and that general risk aversion is prevailing in financial markets.
"The kiwi just can't help be caught up in that. It won't be able to perform well in an environment where equities are falling by large amounts."
Yesterday evening at a BusinessDesk event, Finance Minister Grant Robertson said the best-case scenario for the spread of the coronavirus is becoming much less likely and, rather than a short, sharp shock in the March quarter, it is likely to affect New Zealand's economy through 2020.
"The best-case scenario was that the containment option would work. That appears to be working in China but it's now becoming much less likely" for the rest of the world, Robertson said.
"That basically means, in terms of New Zealand, we're looking at impacts right through 2020," he said.
Robertson said the government is hoping we won't see the worst-case scenario but "we need to be doing the planning for it, even if we're not expecting" the virus to have a catastrophic impact.
Pepper said Robertson merely confirmed the realisation the market had already come to. It had gone from expecting no further interest rate cuts from the Reserve Bank to fully pricing in a cut by August and has started to price in another cut beyond that.
Analysts are now reassessing earlier assumptions that the virus impact would be confined to depressing March quarter growth, Pepper said.
The New Zealand dollar was at 95.90 Australian cents from 95.67 at 5pm yesterday, at 48.67 British pence from 48.61, at 57.67 euro cents from 58.12, at 69.34 yen from 69.77 and at 4.4143 Chinese yuan from 4.4331.
The two-year swap rate eased to a bid price of 0.9457 per cent from 0.9743 yesterday while 10-year swaps fell to 1.2450 per cent from 1.2975.
