COVID: nonpharm interventions work!!!

a Hong Kong study suggested a large benefit from non-pharmacologic interventions in decreasing the spread of SARS-CoV-2 (see covid hong kong nonpharm interventions lancet pubhlth2020 in dropbox, or doi.org/10.1016/S2468-2667(20)30090-6).

Details:

--the approach to Covid-19 in Hong Kong was been: intense surveillance for infections, both in incoming travellers and in the local community, with 400 outpatient and 600 inpatient tests/d by early  March

    --those with positve tests were isolated in the hospital until clinical recovery and no further viral shedding

    --close contacts were traced from 2 days before illness and quarantined in special facilities.

    --and community-wide social-distancing/behavioral changes were implemented to decrease community-transmission from SARS-CoV-2 positive people not identified by their symptoms or being close contacts

--the researchers attempted to quantify the effect of these containment measures for Covid-19; and they assessed the prior epidemiology of influenza outbreaks to see if the added intense non-pharmacologic interventions against SARS-CoV-2 changed the epidemiology of influenza

    --the influenza data was based on sentinel surveillance of influenza-like illnesses (ILIs, defined a s fever plus cough or sore throat) from a network of 60 general outpatient clinics, for the 2010-11 and 2014-15 seasons

--they also did 3 surveys of peoples' attitudes in 2020: in 1/20-23, 2/11-14 and 3/10-13

--they assessed changes in the effective viral reproductive number (which they refer to as R₁, as opposed to what we call R₀)

Results:

--confirmed cases of SARS-CoV-2: 715 by 31March

    --imported cases from outside Hong Kong: 386 ("imported cases")

    --linked to other known cases: 187 ("linked case")

    --unable to be linked to others: 142 ("unlinked cases")

--of these cases:

    --94 asymptomatic

    --621 symptomatic

--from their graph of interventions and cases (figure 1), by date of symptom onset:

    --pretty even distribution of imported/linked/unlinked cases prior to Feb 1 ( about 25-30 cases total for all of January)

    --by 1/25 there was flight suspension to/from Wuhan, closure of theme parks, quarantine of people with travel history, augmented closure of border control points

        --in February, also ony about 3 new cases/d, with pretty rare imported cases, and more unlinked than linked

    --enhanced lab surveillance at clinics began early March, but  around March 10 imported cases significanlty dominated the new cases (with new cases now averaging about 20/d)

    --by March 20 there was expanded virus testing of inbound travellers, including asymptomatic ones, with significant decreases in new imported cases

--R₀: began in Feb around 2-2.5, decreased to 1 in mid Feb, continued to decrease to about 0.5 by the end of Feb, then after a bump in early March, decreased to about 1 by March 6 and remained a little over 1 for the rest of March

--For the influenza A H1N1 outbreak in 2019-20:

--R₀ started around 1.5 in Dec 2019, then increased dramatically until jan 26, then plummeted more precipitously over the next 2 weeks that precisely correlated with school closures for holiday (Chinese New Year), with an associated 44% decrease in flu transmissabilty

    --the R₀ from pediatric hospitalization rates also decreased from 1.10 to 0.73, a 33% decline

--similar but much less dramatic decreases occurred with school vacation in prior flu seasons in 2010-11 and 2014-15, more in the 15% range

the survey found a dramatic increase over time in those wearing masks when going out and avoiding crowded places, reflecting increasing anxiety about Covid-19 as the pandemic spread, and likely further decreased viral transmission.

Commentary:

--in China, outside of Hubei province, they implemented aggressive public health measures: massive mobility restrictions; universal fever screening in all settings; and neighborhood-based household-focused social distancing enforced by teams of community workers.  Also a "pervasive deployment of artificial intelligence-based social media applications and the use of big data" (ie, Big Brother is watching you...).  this brings up a couple of issues:

    --this Chinese approach would be rather difficult to implement in the US or most other countries, hence the importance of looking at a potentially more generalizable model, such as in Hong Kong

    --it still took 4+ months for China to suppress the virus enough that life in Shanghai, for example, is back to normal now. (this is from a friend living there)

    --the US, where we have done a much much much less aggressive approach overall (ie, some areas have been pretty aggressive, much of the country far less), we are likely not to return to normalcy for much more than the 4+ months as in China, especially with the misguided efforts of our much-too-fearless leader to restore the economy in time to help his re-election, and several states already relaxing their social-distancing and other nonpharmacologic interventions

        --and, per the CDC director Robert Redfield, the second wave of Covid-19 will likely conincide with the flu season, putting an "unimaginable strain on the health-care system" and further limiting medical supplies/hospital beds that will be needed for each of these infections (see https://www.washingtonpost.com/health/2020/04/21/coronavirus-secondwave-cdcdirector/ ). Redfield noted the White House is about to release their guidliness for a gradual reopening of the country.......

--the comparison of Covid-19 with flu epidemics is really interesting, and highly suggestive. 

    --the presumed major transmission of both is similar, as well as the fact that both are transmitted easily in the early symptomatic period and that both can be transmitted from asymptomatic people

    --there has been a consistent benefit in flu transmission associated with the school recesses for the Chinese Lunar New Year celebration

    --so, there is likely utility in looking at the added effects of the intense Covid-associated increased confinement, self-distancing, and other nonpharmacologic interventions on the epidemiology of flu during this same period

    --one interesting side-line that should be studied is the role of kids in transmission of SARS-CoV-2 (since they are so important in flu transmission): we do know that children overall do better than adults. but is that because they do not get infected as easily? or because they are often asymptomatic or more likely just to have minor symptoms from SARS-CoV-2 (and be dismissed as yet another URI in kids that already get so many)?? i did see some early Chinese data suggesting that their actual infection rate is not so different from other age groups, but we really do need good epidemiologic studies to really understand the prevalence of SARS-CoV-2 in different age groups (meaning lots and lots of testing, including asymptomatic people), and perhaps even looking at the genetic fingerprints of the virus as a means to understand specific transmission chains between people (coincidentally, this genetic fingerprinting was done, per an article in the NY Times this am, finding that there were several US cases in mid-January that predated those in Washington state; they were all over the country; and that in general there seems to be about 2 small mutations/month in the virus, giving the researchers strong evidence to assess the lineage and transmission of the virus: see https://www.nytimes.com/2020/04/22/us/coronavirus-sequencing.html?campaign_id=9&emc=edit_NN_p_20200422&instance_id=17849&nl=morning-briefing&regi_id=67866768&section=topNews&segment_id=25713&te=1&user_id=44a0ffdebe23c4195e1f7dab1c01b52e . This technique was used in the Munich study as well to show that virus replicated in both the lungs, with their ACE2 receptors, as well as in the upper respiratory tract, which are relatively ACE2 deplete: see http://gmodestmedblogs.blogspot.com/2020/03/covid-19-update-31120.html )

--the argument in the Hong Kong study is basically that the much more dramatic decrease in flu this past year (44%) was much greater than the 15% of so reduction in these past flu seasons during the same periods of school vacation, and that this current dramatic reduction was likely associated with adding on the various nonpharmacologic interventions for Covid-19 on top of the usual school vacation. [ie, their nonpharmacologic interventions for Covid-19 played a really important role in decreasing flu, and since there are so many similarities between flu and SARS-CoV-2, these Covid-19 interventions were very likely really effective in decreasing SARS-CoV-2 transmissability

--that all being said, it still is a leap of faith to conflate the SARS-CoV-2 directly with flu. 

     --for example, SARS-CoV-2 is more contagious than flu (higher R₀), meaning that it will take more aggressive interventions and likely longer to control than flu [an R₀ of <1 suggests that the infection rate is pretty low and likely to be stable, and then peter out over time, with herd immunity etc]

--but, all of this

    --which really goes straight in the face of the current trend in US policies.

    --and these poorly-conceived policies (from a public health perspective) will likely lead to a very long and drawn-out Covid-19 course, with likely 2nd and 3rd waves and affecting the whole country

--so, nothing so surprising, really:

--with increasingly aggressive surveillance, monitoring and limitations, Hong Kong was able to reduce the transmissability of SARS-CoV-2 to an R₀ of about 1 within a little more than a month, meaning that though cases were increasing, they were in a good position to effectively eliminate the virus within a few month period thereafter, as was done in mainland China with very aggressive policies (though still likely to take longer to eliminate in Hong Kong as has been done in at least some areas in China that we have data for)

--and the data from flu, which seems to share many characteristics with SARS-CoV-2, reinforce (again not surprisingly) that the nonpharmacologic interventions (self-distancing, restricting travel, etc) are extremely important in decreasing the R₀. 

--and, the real reason i am doing this blog, is to underscore as much as i can how wrong it is to relax nonpharmacologic interventions, as is currently happening in some areas of the US and about to spread more rapidly (and, unfortunately, with the attendant more rapid spread of the virus)

    --and, perhaps leading to a renaming of Covid-19 to Covid-19-to-21-or-so, with its longterm ravages on peoples' health as well as the economy and all of our social structures

geoff

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