This is a case update. I’ll also discuss a hack for poorly ventilated areas, the paper from Israel everyone is talking about, as well as the new variant, the Mu variant.

For the US, it definitely looks like we’ve cleared the peak for the US. Cases in many states have started to go down. States in which case numbers are still rising include Utah, West Virginia, Maine, and Pennsylvania. A word of caution is that COVID spreads indoors in poorly ventilated areas. Last Summer, we had large case loads in the South, and the winter had even larger case loads starting in the North. Both phenomena were probably caused by the virus spreading indoors, where there was air-conditioning and heating respectively. As Summer ends, we may end up seeing a large number of cases starting from the Northern states and spreading south, just like we did last Fall. If this happens, it will likely begin in October.

Cases continue to fall for California and San Diego County.

Indoor virus filter: I recently heard a podcast from physician Mike Osterholm (Osterholm Update, Episode 66). He argued that indoor ventilation was actually much more protective than masks. For those who can’t ventilate a space well, he suggested making a large scale air filter (Corsi box) using a box fan and a MERV 13 air filter. This is equivalent to a number 10 Honeywell furnace filter like you’d get at Home Depot. If you have a space where people gather that you can’t ventilate, buy a filter roughly the same size as your fan and tape it firmly to the front of the fan. Make sure the filter supports are toward the fan blades. On a side note, he also argues as I do that loose fitting masks are nearly worthless, but N95, KN95, and KF94 respirators are very good.

Data from Israel: Lots of folks are talking about the pre-print paper from Israel (Gazit et al) on vaccination vs natural immunity (infection by COVID). The data was from a database of patient information. They compared breakthrough infections (a person who was vaccinated and later was infected with Delta) to reinfection (a person who was infected with a previous SARS-2 variant and was then infected with Delta). They did this as a whole and also in a time matched way, meaning that the date of likely infection was around the same as the date of the 2nd dose of vaccine. Note that the vaccines are against the original Wuhan strain, so the paper is also discussing the rate at which Delta infects those who had natural vs vaccine exposure to non-Delta strains.

The results show that naturally infected people were almost 6 times less likely to get infected by Delta than vaccinated people, and 7 times less likely to have symptoms. The results are even more striking for the time matched data. For these patients, naturally infected people were 15 times less likely to get infected, and 27 times less likely to be symptomatic. Over all, it looks like natural immunity is better than vaccination for resistance to the Delta Variant.

They did another study comparing natural immunity to natural immunity plus 1 dose of vaccine. Those previous infected with COVID AND having 1 dose of vaccine were about half as likely to be infected with Delta. Or you could say that having 1 dose of vaccine made them almost twice as resistant to reinfection.

Some cautions are in order. Countries are not responding to the Delta Variant in exactly the same way. As discussed before, countries with large vaccination programs are seeing much fewer deaths due to Delta than other countries. However, rates of infection in vaccinated people by Delta seem to be higher in Israel, suggesting a slightly different version of Delta is in that country. Some reports suggest the Pfizer vaccine is only 39% effective against Delta in Israel.

The Mu Variant: News is only starting to circulate regarding the Mu variant (pronounced “mew”). First detected in Colombia in January 2021, this variant is currently classified as a Variant of Interest, not a Variant of Concern, suggesting it does not have characteristics that are very different from other versions, and may not have a large impact. A recent paper from Italy suggests that currently available vaccines do neutralize Mu, although with less efficiency. On the other hand, a WHO press release suggested that it may be able to escape immune responses raised to other variants. Since there is some disagreement, more studies will need to be done.

Don’t fear, but be smart!
Erik