key: cord-0741093-bpgt8ok8
authors: Walach, Harald; Hockertz, Stefan
title: A reply to Dr. Pan’s and Dr. Wu’s response: “Wuhan COVID-19 data – An example to show the importance of public health interventions to fight against the pandemic”
date: 2020-06-12
journal: Toxicology
DOI: 10.1016/j.tox.2020.152524
sha: 8d4869432e1bf0f96729cf2c4315cefc1445fee9
doc_id: 741093
cord_uid: bpgt8ok8

nan

Toxicology journal homepage: www.elsevier.com/locate/toxicol Reply to the letter to the editor A reply to Dr. Pan's and Dr. Wu's response: "Wuhan COVID-19 data -An example to show the importance of public health interventions to fight against the pandemic"

We are grateful to Drs. Pan and Wu for their clarification. In fact, it would have been useful, if this additional information had been clearly presented in the original paper. Obviously, containment of a spreading infection is the optimum, if at all possible. This seems to have been successful in Taiwan and Hongkong, because of the special geographic situation (Cheng, Jian et al., 2020; Cowling, Ali et al., 2020) . But containment of such an infection in an interconnected world is next to impossible; the lockdown of Wuhan airport slowed the progress of the virus into mainland China by 2.8 days only, and the most effective measures seem to be small scale tracing and quarantining of cases and not large scale lockdowns (Tian, Liu et al., 2020) .

Our goal was to point to neglected facets of the data. Even if we look at the lab-confirmed cases (original Figure 1 in. (Pan, Liu et al., 2020) ), we see that the true turning point of the number of cases is the 26 th of January, just three days after the cordon-sanitaire and the lockdown of the city became effective. We therefore respectfully disagree: the lockdown and the public health measures could not possibly have been causal for the decline of infection numbers. Since the delay between contact with the virus, infection and becoming a lab confirmed case is, when considering all data, a minimum of 5 days, we have to backdate the peak of case numbers by about 5 days to reach the peak of the infection which brings us to January 21 st as the turning point of the infection, before any large-scale public health measures have been implemented, and whether casual individual wearing of face masks and closure of schools could have prevented the spread of a virulent infection is very doubtful to us.

The same structure of data is revealed by more recent analyses of German data (Homburg, 2020; Kuhbandner, Homburg et al., 2020; Wieland, 2020) . In each and every situation an analysis that takes into account the delay between becoming infected, testing positive and becoming an official case shows: the peak of the infection is already reached before any public health measures are implemented. It takes about 30 days for the infection to reach a maximum of infected cases. If the population density is high, this happens even more quickly (Wieland, 2020) .

Why, then, did cases decline? Were public health measures responsible? We doubt it. The Wuhan data, as well as other data do not support this conclusion. The data from clearly delineated populations, such as from the cruise ship Diamond Princess (Russell et al., 2020) , or all traced contacts of the first 100 Taiwanese cases (Cheng et al., 2020) speak a clear language that is supported by a new modeling study (Gomes et al., 2020) : the virus does not infect everyone indistinctly. Obviously, natural immunity can prevent a lot of infections (Schäfer and Baric, 2017) which is the reason, why Gomes and colleagues (2020) estimate that only 7%-18% infected persons in a population are enough to reach herd immunity. This is actually good news helping science to understand this infection, and it was our goal to point to this feature of the infection, which was already visible in the Wuhan data (Pan et al., 2020) .

The authors report no declarations of interest.

Contact tracing assessment of COVID-19 transmission dynamics in Taiwan and risk at different exposure periods before and after symptom onset

Impact assessment of non-pharmaceutical interventions against coronavirus disease 2019 and influenza in Hong Kong: an observational study

Individual variation in susceptibility or exposure to SARS-CoV-2 lowers the herd immunity threshold

Effectiveness of corona lockdowns: evidence for a number of countries. Econ. Voice in print

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