A study published today confirms that our first official case was not in fact our first case.
A year ago today, we woke up in Aotearoa New Zealand in our bubbles. We were at alert level four. For me, it was the first time in more than two months that I’d properly slept. I’d been following the WHO’s situation reports about the mysterious illness in China from about mid-January 2020. By late January I was starting to lose sleep. By early March I’d lay awake at night wondering how close we were to the disaster unfolding in Italy and Iran and Spain. Waking in my bubble that morning, I knew we’d given ourselves the best chance of stopping our hospitals from being overrun and saving lives.
It’s both fascinating and depressing looking back at the global Covid timeline now. The first recorded case of the virus had been in Wuhan on December 1, 2019 – hence the name Coronavirus Disease 2019, shortened to Covid-19. The genetic sequence of the virus responsible, SARS-CoV-2, was shared by Chinese researchers on January 12. That allowed German researchers to develop a PCR test, which the WHO quickly shared with the world. The next day, the first case outside of China was confirmed, in Thailand. It was in a woman from Wuhan who had arrived in Bangkok on January 8.
Over the next few days, cases were confirmed in the US, Singapore, Hong Kong, Macau, Taiwan, Vietnam, Nepal, Japan, South Korea, Canada, Malaysia, and France. All were in people travelling from China. New Zealand shut its borders to foreign nationals travelling from, or transiting through mainland China, on February 3. What we now know was that the virus was already circulating in other countries. We were notified of our first official case on February 28, in someone who had returned from Iran a couple of days earlier. Iran had only reported its first case on February 19. Yet already the virus had made it from there to New Zealand.
A new paper out today in the New Zealand Medical Journal by Dr Elizabeth Becker, Dr Richard Vipond, and Dr Chris Mansell from Waikato District Health Board confirms that our first official case was not in fact our first actual case. There was another just a few days before, in someone who had arrived from the Lombardy region of Italy on February 23. Italy had reported its first case on January 31. A few days before our visitor arrived, parts of Lombardy were beginning to go into lockdown. They had only had 16 confirmed cases at so alarm bells weren’t ringing very loudly. That’s why, when the person went to see a doctor on February 25 suffering from a flu-like illness, they didn’t meet the Ministry of Health’s definition for Covid testing. Instead, they were told to self-isolate until they felt better. Which they did. Over the next four days, six other members of their household came down with the same symptoms. They also stayed home. Thank goodness.
You may well ask why we weren’t testing everyone with symptoms if they’d recently arrived from anywhere overseas. It’s a good question. The answer is that we didn’t have the testing capacity yet. Or enough reagents. Everything came from overseas and there were real concerns of global shortages. I remember emailing my lab asking if we had any RNA extraction kits that we could donate should they be needed. Other researchers were doing the same.
The way the Italy-linked case was discovered is interesting. In September last year, one of the household went to get tested as they had symptoms that could have been Covid-19. The result came back as weakly positive. That happens when someone is either at the start of their infection, or if they have been infected in the past and the test is just picking up bits of viral debris. Under these circumstances, what we do now is test the person’s blood for antibodies which can confirm if they’ve been exposed to the virus in the past. In other words, whether they can be considered an historical case.
We know that people can test positive for the virus months after they have recovered. The blood tests showed the person had antibodies, and when the other people in their household who had also had symptoms back in February were tested, they had antibodies too. They’d all had Covid-19. The visitor from Lombardy was also found to have antibodies to the virus when they got tested back to Italy so is most likely to have been the source.
Several months ago, Dr Jemma Geoghegan and colleagues showed that Covid-19 entered New Zealand multiple times from all around the world. Their analysis and that of many others has shown that the SARS-CoV-2 virus, or the original variants at least, obey the Pareto principle, aka the 80/20 rule. That is, 80% of cases will only infect one or two other people, or maybe even no one else. But the other 20% result in the majority of cases. We’re fortunate this earlier case didn’t turn into a larger cluster.
Studies like that by Dr Becker and colleagues may well reveal we had a few more cases bubbling along undetected before we moved in to alert level four. We know from the lack of deaths and hospitalisations that there can’t have been too many, or that they didn’t get too large. Even so, choosing to follow an elimination strategy when we did was clearly the best way to stop the chains of transmission we had. You only have to look at the countries that chose to try suppression instead to see how badly things could have gone for us.
