The Count

Region	Cases	Deaths
World	9,876,419	495,418
US	2,545,946	127,353

Research News

Immune response to SARS-CoV-2 infection may differ markedly depending on disease severity. An Italian study of 64 COVID-19 patients with a range of disease severity found that asymptomatic or mildly symptomatic disease was associated with a marked NK (natural killer) cell response and a transient rise in IgA, while severe disease was associated with a sustained IgG response. This could have major implications for our understanding of the incidence of asymptomatic disease and the transmission of the virus.

Genes for the SARS-CoV-2 receptors, ACE2 and TMPRSS2, did not demonstrate strong links to positive tests for the virus in UK Biobank Subjects An analysis of the 74 (out of 49,953) UK Biobank subjects known to have tested positive for SARS-COV-2 during a period when most testing was done on hospitalized patients concluded that there was no association between the genes for either receptor site and what is likely to have been severe disease. Note that this study only compared genes between those with and without positive tests. It did not compare severity within a group of infected subjects.

Hospitalization for COVID-19 associated with ACE2 genotype A comparison in a group of 62 patients who tested positive for SARS-CoV-2 between those who were hospitalized for COVID-19 and those who were not hospitalized identified six single nucleotide polymorphisms (out of 61 evaluated) associated with hospitalization. These results need to be validated in other data given the potential for a chance association in these data. If these results hold up they may point to an important indicator of genetic susceptibility for severe disease.

Analysis of the global library for the SARS-CoV-2 genome finds no evidence of increase in viral transmission. A team of British researchers searched through genetic data from 24,000 samples of the virus, looking specifically for the repeated emergence of variants that conferred a selective advantage to the virus as measured in the spread of the viral genotype. Using this approach, they found no evidence of viral evolution towards a more transmissible form. Other researchers have reached the opposite conclusion, most recently a team from Northwestern, which looked at patient level data and found an association between viral clades and viral lodes in the upper airways. It seems likely that the debate about viral evolution, transmission, and disease severity will remain active for the foreseeable future.

A study of contact tracing data demonstrates the occurrence of SARS-CoV2 infections with symptoms and cellular immunity without sustained IgG response. A French study of seven families with nine index patients with mild disease and eight contacts, six of whom developed symptoms. All cases develop both humoral (antibody) and cellular response to the virus. The six cases did not develop antibodies, but did develop signs of a cellular response. These data raise the possibility that antibody testing may not be a sensitive tool to detect infection because cellular immune response can develop in the absence of an antibody response.

Seroprevalence of SARS-CoV-2 antibodies strongly associated with age An Italian study of 4,174 people found a strong relationship between age and seroprevalence, which ranged from 9% in children under 5 to 42% in people over 90. Based on the studies above, it is conceivable that this is related to disease severity by age category.

Rate of undetected cases in Iceland may be as high as 90% A team from Harvard and MIT analyzed seroprevalence data from Iceland and concluded that initial screening missed 89-93% of cases and broader screening missed 80-90%. The author's caution that a false positive rate as low as 0.5% (with no false negatives) would imply a true undetected rate of 0%.

Detail, longitudinal study of SARS-CoV-2 seroprevalence demonstrates effectiveness of public health measures 760,000 assays conducted on 5500 pre-pandemic and 26,000 co-pandemic samples from hospital patients and healthy blood donors in Zurich determined a prevalence of SARS-CoV2 antibodies in both sets of samples that peaked at to the virus in 0.8-1.6% in early April, shortly after the introduction of stay home measures. The three part testing protocol is by far the most careful and accurate testing done to date. The authors conclude that this indicates a true number of infections that is 5-10 times the number of reported cases of COVID-19 and an infection fatality rate of 0.5%.

COVID-19 patients have high rates of thyroid dysfunction that increases with disease severity A Chinese study of 62% of patients have depressed levels of TT3 and TSH (Total Triiodothyronine and Thyroid Stimulating Hormone). 75% of patients with severe disease had thyroid dysfunction as compared to 24% of patients with mild disease. This may indicate that the virus attacks and damages the thyroid pituitary axis. The authors conclude that thyroid function should be monitored in COVID-19 patients during both treatment and follow-up.

Platelets in COVID-19 patients found to contain SARS-COV-2 RNA Moroccan and Canadian researchers demonstrate that, not only do platelets contribute to thrombosis and inflammation in COVID-19, but, in 20% of cases, they contain viral RNA. This documents a previously undescribed way for the virus to both influence the disease process, but also, potentially, to distribute the virus.

Children and Younger Adults may play a key role in super-spreader events An analysis of superb-spreader events in Georgia concludes that 2% of cases caused 20% of all infections and that those under the age of 60 are 2.4 times more likely to cause these events than adults over 60. This suggests that those under 60 play a key role in spreading the virus given the unique importance of super spreader events.

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Unless otherwise noted, these pre-prints are not peer reviewed.

Recent Posts Covid19- Ahead of the Curve.

The Epidemiology of Political Rallies: Trump supporters dying for reelection Packing thousands of people together in an arena (or even a church) in a city where COVID-19 cases are spiking to yell, chant, and cheer for a couple of hours with no masks on was a really, really bad idea. To see how bad, let's do the math.

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