Drive-in church likely virtually guarantees everyone — the entire family — in a car will be infected with covid-19 before the closing prayer if just one person gets in the car unaware they are already infected in many instances.

The unaware, infected family member gives it to everyone else in the car in such instances.  People forget how small a car-cabin and its air volume truly is.  The infection risk in the non-moving car for such a prolonged time appears likely to approach 90-99% in relevant scenarios.  Meanwhile, the infection rate in the home for exposed household members for covid-19 is low.

Very High Risk for Whole Family in Non-Moving Car for That Long

Sitting in a non-moving car for such a long time is a worst-case-type environment for virus transmission — enclosed space, in spitting-distance, prolonged, no break, mouths aligned, tiny air-volume, breathing same air, sometimes air recirculating, low air-flow, closely surrounded by surfaces on which covid-19 lives, little space for expelled virus droplets to disperse, immobilized people, and nowhere to escape virus droplets projected by coughing, sneezing, singing, or otherwise.

There is a 90-99% risk of infection after just 45-60 minutes in a car with a person already infected with the flu in some relevant scenarios, per a peer-reviewed study by Australian researchers and doctors at Queensland University of Technology.  Covid-19 appears just as contagious as flu, if not more so. 

In-Home, Much Lower Risk

Two Harvard professors and the chair of the engineering department at Portland State explain in USA Today that in the home it is “not as easy to spread COVID-19 from one person to another.”  They explain:  “In the car, it’s a whole different ball game.”

Indeed, a 90-99% risk of infection in the car presents a much higher risk of infecting everyone in the car during drive-in church than there is of ever infecting even a single other person that is in the home in many situations in light of these studies, experience with other viruses, and the difference in in-home and in-car environments. 

Household transmission rates (secondary attack rates) for covid-19 have been comparatively low, 3.0 – 10.5% symptomatic, per three independent studies cited by the Centers for Disease Control, National Institute for Health and the Korean Centers for Disease Control and Prevention, and the World Health Organization.

The purpose behind the CDC’s guidance to wash hands, disinfect, and take other precautions at home is to help avoid infection at home.  Parents and children, for example, frequently washing hands can help avoid virus intake or avoid taking in enough virus in a concentrated enough time to overcome their immune system and cause infection.

And experience with other viruses, like the flu, indicates that just because one person in the home has it does not necessarily mean everyone will get it, certainly not approaching 90-99% transmission for all.

Immune Systems Can Prevent Infection Despite Some Amount of Exposure

Estimates are that up to 50% of those infected with covid-19 are asymptomatic.  Asymptomatic persons may generally be “not very contagious,” but the attributes of asymptomatic persons remain unclear.   

The rate at which they give off the virus (sometimes called quanta production) may be low enough that immune systems of other family members can handle periodic intake of such lower amounts of virus occurring in-home over time.  That is, immune systems can keep other family members from becoming infected despite periodic exposure to lower amounts of virus.  The amount of covid-19 generally giving rise to infection and its profile is not yet known with specificity.

The World Health Organization explains, though, that generally the risk of catching covid-19 from the asymptomatic is very low.

One Contributor of Increased Risk in Car:  Accumulation of Virus Droplets in a Small, Enclosed Air Volume in Which Everyone Remains Over a Long Period

In the car, as the Harvard and Portland State professors explain, “it’s a whole different ball game.”

Having the whole family suck on a few larger party balloons containing more and more virus droplets while sitting closely together in a small, steel box with ceiling and walls just inches or feet away containing the same is not far from the scenario of all getting into a car for drive-in church with one family member already infected unaware in many situations.

The professors explain in USA Today that “Over the decades, we’ve done a really nice job of sealing up our cars. Ever notice how quiet they are on the inside these days? That’s because every effort has been made to seal up every gap possible so there are better acoustics.”

They observe that “When the windows are closed, SARS-CoV-2 (in fine aerosol particles) accumulates in the car cabin.  With each new cough, the concentration builds up with no significant dilution happening.”

Note that concentration builds up with coughing, sneezing, breathing, and singing.

They pointed out that in a moving car, cracking a window can help much with the in-air droplets.  A non-moving car was not addressed.  And opening a window is prohibited by multiple governmental entities and churches at drive-in church.

But it appears rolling a window down in a non-moving car does not help much, if at all, as the air changes per hour (ACH) in a non-moving car with a window down is nearly exactly the same as the ACH in a car moving at up to 72 mph with windows closed and air ventilation off (6.5, 6.6), per a Stanford University study, thus likely yielding a similar concentration of covid-19 particles building up in the car cabin as it sits at drive-in church.

Of course, rolling down a window can hurt, as the wind can blow particles from an infected person into the faces of uninfected in the back seat or in the next car.

And the in-air difference is just one of the worst-case differences between in-car and in-home described above that cause infection risk in the car for so long to go way up.

Suffering and Dying Alone

A meaningful percentage of those infected with Covid-19 suffer tremendously and a number die.  These victims, even children, often suffer alone in the hospital and die alone, with families and friends prohibited from visiting.  This is not a trivial risk as all ages are susceptible, and churches often serve those most vulnerable to the virus.

Government Not Making it Illegal Does Not Mean it is Safe for Your Family

Governments not prohibiting drive-in church does not mean it is safe for families.  Government orders focus mainly on public-health concerns, social-distancing, and larger-scale transmission risks, not private-health concerns or inter-family risks.  And there are constitutional and political issues with prohibiting religious matters.

That one family member might infect another is not generally a public-health concern or an immediate, large-scale threat, as the threat is limited to those in the car.

It is up to church leadership and adults in families to protect against inter-family transmission.

In-Car Gives Opportunities for Infection, Air Volume Tiny Compared to In-Home

Continuous or more-frequent intake over a concentrated period — in car for drive-in church —- at even a lower virus-shedding rate of the “not very contagious” can overcome immune systems, allowing one who might not otherwise infect others to infect everyone in the car.  The drive-in church car-environment, compared to in-home, appears to maximize opportunities for infection in many instances. 

A typical room in a mid-size house has more than 12 times the air volume of a mid-size car.  Even smaller houses have more than 150 times that air volume of a car.  Air recirculation in a car and low air-flow can have a major impact on virus transmission.

In-home, one can step away from a cough or sneeze, avoiding high-volumes of virus droplets and disinfect.  In-car, one cannot step away.

In-home, even sleeping in the same bed together, if the infected person engages only in shallow breathing and not sneezing and is “not very contagious” in such a wide-open room, for example, it is possible for the non-infected to avoid infection.  Infection is certainly a substantial risk there, but not inevitable before the infected notices symptoms and isolates or recovers.

In-car during drive-in church, breathing is not shallow and is normal or excited — indeed, singing likely projects droplets and promotes transmission — and the shared air-volume is often around 5-9% of a typical bedroom.  In-car, if the flu study is any indication, the risk of transmission can be 90-99% for everyone in the car in many instances in time-frames of drive-in church.

Like Frogs in a Jar in a Test-Tube Sucking on Party Balloons in a Small, Steel Box in a Parking Lot in the Sun for a Long Time 

Whether one uses the analogy of a test tube with the family and virus in it, frogs in a quart jar, people sucking on party balloons, or a steel box with a low ceiling dropped over the family, the message suggested by the flu study and covid-19 findings is the same:  getting in a car for drive-in church likely virtually guarantees every single person in the car will be infected with covid-19 in many instances if just one of them unknowingly gets in the car with the virus, while they all have a very good chance of avoiding it at home.

Growing Threat

Drive-in church may have been low risk in many places several weeks ago.

But as the virus spreads, and with up to 50% of those infected asymptomatic, the odds that a family member is infected unaware and that one or more cars in the church parking-lot will contain an infected person increases dramatically.

Confirmed cases double roughly every 5-8 days in many places.  With incubation and testing delay, confirmed cases today are for infections occurring about 2 weeks ago or more, and there are many unconfirmed cases for every confirmed one, as testing is limited.

Of course, these observations do not apply just to drive-in church.  Few scenarios, though, involve such large numbers of people in non-moving cars for so long.

Some Church Leaders Have Cancelled or Warned Members

Some churches cancelled drive-in church in favor of online or warned members of this inter-family risk.

Conclusion — Online Only for Now; if Proceed, Consult, Warn, and Aid

Churches should consult physicians and their health department about this specific issue, increased transmission-facilitation between family members and significantly increased risk in-car.

I recommend not having drive-in church and instead providing online and phone services during this time.

If church leaders decide to proceed despite the danger, they should clearly and unambiguously warn potential attendees about this specific risk.  Families should be equipped to knowingly assess this risk, including considering the likelihood one in the family is infected and the heightened risk to certain family members.

Communicating is fraught with issues, though, including not reaching everyone timely.  And, of course, those most at risk (elderly, etc.) often feel compelled to attend if church leaders hold services.

A church proceeding despite this danger should also, with physicians and a health department, develop ways to lessen the danger and clearly advise such attendees how.

Being patient in this uncertain time and kindly not holding or cancelling or not attending drive-in church is the only way of protecting fully against this threat to the family, leaving room for the reasonable hope that uninfected family members avoid infection in-home.

“Love is patient, love is kind. … It always protects, … always hopes ….” (1 Cor 13:4-7)

Prayers and good luck to all.






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Sources & Notes

For more information and additional citations to sources used, see Steve Gardner, “Drive-in Church Danger for Families:  Increased COVID-19 Risk,” (March 28, 2020) (the text and the Sources & Notes section).  The present article includes much of the March 28 article in shorter form.

Also see Steve Gardner, “10 Reasons Churches Should Not Have In-Person Services for a Time: COVID-19 and Flattening the Curve,” (March 14, 2020) (see text and Sources & Notes section).