intra-household contagion

In this paper, we explore different channels to explain the disparities in COVID- 19 incidence across New York City neighborhoods. […] We find evidence consistent with higher intra-household contagion as days go by. […] Although commuting patterns have been put forth as a major factor in the spread of the disease in NYC, we show that, after including occupation controls, they fail to significantly explain variation in share of positive tests at the zip code level. [Previously: Home outbreaks were the dominant category, followed by transport]

In NSW, from March to mid-April 2020, 18 individuals (9 students and 9 staff) from 15 schools were confirmed as COVID-19 cases; all of these individuals had an opportunity to transmit the COVID-19 virus (SARS-CoV-2) to others in their schools. 735 students and 128 staff were close contacts of these initial 18 cases. One child from a primary school and one child from a high school may have contracted COVID-19 from the initial cases at their schools. No teacher or staff member contracted COVID-19 from any of the initial school cases. [NCIRS]

The proposed full scale model (applied to real COVID-19 dynamics in London, Moscow and New York City) shows that top 10% spreaders (100+ higher viral loading than median infector) transmit 45% of new cases. Rapid isolation of superspreaders leads to 4-8 fold mitigation of pandemic depending on applied quarantine strength and amount of currently infected people. New testing strategy may prevent thousand or millions COVID-19 deaths requiring just about 5000 daily RT-PCR test for big 12 million city such as Moscow. [medRxiv]

We find that mass-testing is much less effective than testing the symptomatic and contact tracing, and some blend of these with social distancing is required to achieve suppression. […] Even with an expectation of less than one new case per person, our model shows that exponential spread is possible. […] Without full lockdown, mass testing of the general population to search for unknown infected individuals is mostly futile for containment, since it would require near universal testing to be effective, which is far beyond current capacity. […] To create containment, we need to test 30% of the population every day. If we only test 10% of the population every day, we get 34% of the population infected – no containment. [Modeling COVID-19 on a network: super-spreaders, testing and containment]

We use mobile-phone-data-based counts of 11,478,484 people egressing or transiting through the prefecture of Wuhan between 1 January and 24 January 2020 as they moved to 296 prefectures throughout China. First, we document the efficacy of quarantine in ceasing movement. Second, we show that the distribution of population outflow from Wuhan accurately predicts the relative frequency and geographic distribution of COVID-19 infections through February 19, 2020, across all of China. Third, we develop a spatio-temporal “risk source” model that leverages population flow data (which operationalizes risk emanating from epidemic epicenters) to not only forecast confirmed cases, but also to identify high-transmission-risk locales at an early stage. Fourth, we use this risk source model to statistically derive the geographic spread of COVID-19 and the growth pattern based on the population outflow from Wuhan. [Nature]

Chinese scientists report that they captured tiny droplets containing the genetic markers of the virus from the air in two hospitals in Wuhan, China, where the outbreak started. It remains unknown if the virus in the samples they collected was infectious, but droplets that small, which are expelled by breathing and talking, can remain aloft and be inhaled by others. Scientists do not know yet whether the viruses remain infectious or whether the tests just detected harmless virus fragments. [NY Times | Nature]

The new serological data, which is provisional, suggests that coronavirus infections greatly outnumber confirmed covid-19 cases, potentially by a factor of 10 or more. Higher infection rates mean lower lethality risk on average. But the corollary is that this is a very contagious disease capable of being spread by people who are asymptomatic. […] an infection fatality rate between 0.5 and 0.8 percent, depending on which death toll is factored in. […] A rate of 0.5 percent “is way more than a usual flu season and I would think way more than the ’57 or 1968 [influenza] pandemic death toll, too,” Viboud said. […] Epidemiologists have said somewhere between 40 to 70 percent of the population will likely become infected in the next couple of years if there is no vaccine and the public does not take aggressive measures to limit the spread of the virus. “Do the math!” [Washington Post]

Jan Albert, a professor in the Department of Microbiology, Tumor and Cell Biology at the Karolinska Institutet in Sweden: “It’s clear that Sweden had more deaths [than many other European countries] up until now, and that’s probably at least in part because we haven’t had as strict a lockdown and not a lockdown enforced by law. What’s the strategy of the other countries?” he asked. “It [herd immunity] was already the only thing that will eventually stop this, unless there is a vaccine in time, which is quite unlikely. “The truth is that no one, no one in Sweden, no one elsewhere either, knows what the best strategy is. Time will tell.” He said that he believed that stricter lockdowns “only serve to flatten the curve and flattening the curve doesn’t mean that cases disappear — they are just moved in time.” [CNN]

Africa’s youthful population may also help to explain the low death rate so far. The median age in Africa is 19.4 years, compared with 40 in Europe and 38 in the US.

Japan’s northern island of Hokkaido offers a grim lesson in the next phase of the battle against COVID-19. It acted quickly and contained an early outbreak of the coronavirus with a 3-week lockdown. But, when the governor lifted restrictions, a second wave of infections hit even harder. [Twenty-six days later, the island was forced back into lockdown.]

The Belgian government has reportedly been considering allowing people to form “social bubbles” of 10 people. The memo proposed that a bubble of people could spend time together on weekends, as long as all 10 people agreed to socialize exclusively with each other.

In Vilnius, Lithuania, some cafés will be able to set up outdoor tables free of charge