With most countries still in lockdown, some have started to reopen, and the world is watching. What does it mean to have a successful reopening, and have we witnessed it? Looking at the resurgence of Covid cases in China and in New Zealand, some may find it hard to label them as a success. However, what happened there is exactly what countries that achieve very low levels of infection can expect of a successful reopening, at least until the virus is eliminated worldwide.

The first step in controlling the virus is to implement strict stay-at-home procedures and to carry out a rigorous contact tracing effort. Tracing the contacts of all those known to be infected with SARS-CoV-2 allows the community to get ahead of the disease by quarantining anyone who might be infected and infectious, preventing them from further transmitting the virus. Massive testing and immediate contact tracing and mandatory isolation for those exposed is crucial for countries to break the chains of transmission.

Wuhan, the city at the epicenter of this pandemic, once had a total of 68,135 confirmed cases. Today, the provincial health commission announced no new confirmed, asymptomatic or suspected Covid-19 across the entire province of Hubei, where Wuhan lies.

The most recent outbreak in China was in  Beijing. No infections were reported in Beijing for almost six weeks. Then on June 10 a man with no history of recent travel visited a doctor with a fever and chills. He tested positive for SARS-CoV-2 and was hospitalized the following day. While in hospital, public health officials discovered that he had visited a meat market on June 3. Within days, the city was under lockdown, a widespread testing initiative was underway, and thousands of contact tracers were trying to chase down potential new infections. Over a million people were tested within a week. More than 180 people as of Friday were found to be virus positive, all asymptomatic.

Thanks to this effort, a new cluster of infections was identified, all with links to the meat market. While it’s unknown how the SARS-CoV-2 virus was first introduced at the market, after a 55-day run in which there was no known local transmission, the sheer volume of people passing through and the less than hygienic conditions may provide some of the explanation for the spread.

It’s possible to argue that this re-emergence of locally transmitted infections demonstrates the failure of Beijing’s reopening. But in a globalized world where people from countries or communities with high rates of infection are still able to travel freely to communities that have their outbreak under control, the possibility of achieving zero new infections while the global infection rates are high is remote.

A similar situation is occurred in New Zealand. After 17 days without any new infections, the country lifted its Covid-19 restrictions, only to be greeted by two new coronavirus cases just over a week later. Those cases came from two women who traveled from the UK to New Zealand, via Australia. Immediately upon detection they were lodged at an isolation hotel in Auckland and then monitored remotely as they traveled by car from Auckland to their home base in Wellington, where they have been in isolation ever since.

As New Zealand’s director general of health said in a news conference, “A new case is something we hoped we wouldn’t get but is also something we have expected and planned for…. That is why we have geared up, and continue to gear up, our contact tracing at a local level and national capacity and capability as well as having our excellent testing capability so we can respond rapidly.”

That is what a successful reopening looks like. It is not measured in the number of days without any new infections, but rather in the way the public health system responds to a spike in new infections. Until every country is rid of the virus, no country will ever be rid of the virus entirely.

We have the measures at hand to ensure a successful reopening – widespread testing, rigorous contact tracing, and mandatory isolation for those who have been exposed to the virus. With that, we can control the current outbreak, bring infections down to manageable levels in every community, and prevent new outbreaks from overwhelming our healthcare system or leading unnecessary death and injury of those infected.

This article originally appeared on Forbes