LONDON — Germany was lauded for its initial response to the coronavirus pandemic, but a four-week long return to strict public health measures has raised questions over the effectiveness of its strategy second time around.

Germany started its “lockdown light” on Monday, which is set to last for the month of November. The new restrictions include the closure of bars, restaurants, cinemas, theaters and gyms, as well as the re-introduction of physical-distancing measures. 

Chancellor Angela Merkel warned on Monday that Germany “must get the situation under control to a point where the local public health offices can trace contacts again — otherwise the exponential growth will simply spiral further upwards.” 

In the first wave of the epidemic, the country built on existing local infrastructure to get ahead of the virus. Analysis published in the British Medical Journal (BMJ) found Germany’s intensive system of testing, contact tracing, and quarantine were all critical to its “successful control” of the outbreak. 

Dr. Hajo Zeeb, head of department for Germany’s Leibniz Institute for Prevention Research and Epidemiology, told CNBC via telephone that the country’s public health offices tracing system was now being “challenged to its limit.” 

With this second round of lockdown restrictions, the German government said its aim was to push the number of new infections down to about 50 cases per 100,000 people over a seven-day period, so that local public health offices could once again trace all contacts. According to Thursday’s daily situation report by German federal government agency the Robert Koch Institute, there were now nearly 127 cases per 100,000 over a seven-day period.

The government said it was currently unable to trace 75% of new cases. 

Zeeb said a combination of factors had led to the latest upsurge in Covid-19 infections, including a relaxation of restrictions over the summer period. It was people returning to Germany from vacation, however, that was the main driver to the start of another wave, Zeeb said. This resulted in a “major workload” for local public health offices, as they then also had to test these returning citizens. 

“I wouldn’t say it was uncoordinated but there were some strange decisions taken in Bavaria and other places to test people even on highways and in different situations,” he said. 

Bavaria, Germany’s largest state, has had the second-highest number of coronavirus cases in the country, at 119,505, according to data from the Robert Koch Institute.

It is the only federal state in Germany to have rolled out free coronavirus testing for everyone. The move raised concerns it would overwhelm testing centers when it was introduced in June. 

Indeed, Bavaria has experienced testing blunders since it introduced the policy, with backlogs and data entry issues. 

A spokesman for the Bavarian state ministry of health and care told CNBC via email that both of theses issues occurred once and “could be solved quickly.”

“The causes were clearly identified and solved,” he said. “The reasons were in one case a technical defect in a computer system and in the other case a process error or an error during the takeover of the test stations on the freeways by a new supplier.”

Nationally, Zeeb said the spread of the virus had now gone beyond clusters of cases into wider communities, making it harder to pinpoint the source of infection. 

The German government said on Monday that while 21.5 million people had downloaded its Corona-Warn-App, “regrettably only 60% of people testing positive pass on their contacts.” 

The first time round, Zeeb said Germany’s effective handling of the virus was helped by the fact that its epidemic “started in a young age group, which didn’t lead to a lot of severe cases right from the beginning,” giving it more time to prepare its health care system.   

Clear communication of pandemic science, helped by Merkel’s training as a scientist, has also been said to have contributed to its effectiveness. While the historical investment in Germany’s health care system and the rapid response in providing extra intensive care facilities, meant its hospitals didn’t become overwhelmed. 

Dr. Mike Tildesley, an associate professor who specializes in infectious disease control at the University of Warwick in the U.K., told CNBC that in some ways Germany, might be seen as a “victim of its own success.”

Having a smaller first wave meant there were likely to be more people still susceptible to the virus, he explained, making a larger second wave possible.

For Germany, he said the decision to impose another lockdown could be considered “brave,” and may be viewed as Germany acting pre-emptively once again.

Dr. Rowland Kao, a professor of epidemiology and data science at the University of Edinburgh, told CNBC that unless a country manages to get rid of every single case of Covid-19, there’s still a chance of a resurgence when restrictions are lifted.

As such, Kao said it might not be that there’s anything wrong with Germany’s strategy. “It could be that it’s impossible to do it right,” he said, as there are only so many tools at a country’s disposal for containing the coronavirus. 

Kao added that part of what makes the coronavirus so difficult to control is the fact that people are infectious before showing clinical signs. So mildly symptomatic and asymptomatic people contribute to the spread of the disease, meaning “it’s always going to be harder for test and trace to work.”

A spokeswoman for Germany’s federal ministry of health told CNBC via email that there is “an increase in the number of cases when the infection rate generally increases (because of local accumulation of infections, family celebrations or leisure activities).”

“Naturally, more tests are then carried out — without the test strategy changing,” she added.

She said that “shutting down public life again is necessary in order to be able to track infections again.”