There was a 40th birthday party in Connecticut at the beginning of March before the institution of soft isolation measures in the state where at least one partygoer, and possibly more, was infected with COVID-19. People have called this Party Zero because it is believed to be the origin of 88 other cases of COVID-19 worldwide. Apparently, there were at least 100 people in attendance and many of them were from around the U.S., Europe, and South Africa.
According to news reports, the person from South Africa returned sick and was the origin of COVID-19 in that country. Several clusters of COVID-19 in New York City may trace its origin with the party, as well as several strands of the virus in Europe. The party clearly was a watershed moment in the spread of the virus. The party, and hosts, cannot be blamed for the spread of the virus, but it is possible to find an origin of the contact trace to this single event, something which we may not be able to do with other strands of the virus.
Since this party took place at the beginning of March and since we can easily run a quick statistical analysis to inform us of the exponential spread of the virus from this single event, it's likely that up to 100,000 cases could trace its origin to Party Zero. That's likely an estimate that is higher than average, but on the low end we'd still be looking at about 20,000 cases finding their origin with Party Zero.
Recently, it has been discovered that a similar situation has cropped up in New Zealand, according to recent news reports in stuff.co.nz and the New Zealand Herald. See here and here. If the report is correct, there was a wedding party in Bluff, New Zealand before the lockdown measures took effect where at least one member of the wedding party had COVID-19. According to news reports on 10 April 2020 at least 87 people linked to the 21 March wedding tested positive for COVID-19. 25 of those people live in the Waikato region. There were at least 70 in attendance at the wedding event. That's nearly double the number of attendees at the Connecticut party known as Party Zero.
If the statistics from Party Zero are accurate, then we should expect exponential growth in New Zealand, too. By the middle or late of May, there could be up to 50,000 cases linked to the Bluff wedding party. That's an astonishing number of potential cases from the wedding party, but it is not a far-fetched projection statistically speaking.
However, maybe the measures instituted as a part of the Level 4 "lockdown" and the complete border closure of New Zealand will prevent such exponential growth. After all, people who otherwise might drag the virus in from overseas have been virtually prevented from doing so. It's not difficult to imagine that New Zealand has beaten the probability! People who follow the strict "lockdown" guidelines will not be mulling about any New Zealand city, will not be in close proximity to friends and relatives, and will not be spreading the virus even if they happen to be infected.
The working assumption in the above scenario is that the virus spread by community members takes place only in virtue of water droplets spread from one carrier to the next. Such transmission schema, however, is very tentatively supported by the best data. Some medical researchers, like those who work at such prestigious institutions as Princeton University and the Massachusetts Institute of Technology, have suggested that the virus may be aerosolised. If that's correct, then the virus spreads not just through respiratory water droplets or close physical contact but in other ways. But who knows? Some Asian medical researchers have shown that the virus does not become aerosolised; it's strictly confined to the water droplets emitted through coughing or sneezing. According to a reputable microbiologist in Auckland, the use of a nebuliser promoted the aerosolisation of the virus. "Of course," she says, "the purpose of the nebuliser" is to "make the virus airborne." So, clearly it's not aerosolised.
And have no fear! There is no community spread in New Zealand. All of the cases in New Zealand may be traced to overseas travel and foreigners entering the country who were infected by COVID-19. We have heard this refrain from not only from the right honourable Winston Peters but also Prime Minister Jacinda Ardern. It looks like the complete closure of the border will keep out the virus! Exponential growth will not happen in New Zealand because of the measures installed by Level 4 lockdown.
I can easily imagine that the 87 cases we have witnessed cropping up because of the so-called wedding party in Bluff is actually the result of "disaster tourists" (here) renting accommodation in Auckland to get away for a day or two. Remember, the viral threat comes from overseas and people from overseas, and there is no community spread whatsoever.