By Carol A. Kemper, MD, FACP

Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center

Dr. Kemper reports no financial relationships relevant to this field of study.

Things Do Not Always Go Better with Cola

SOURCE: Wuthiekanun V, Amornchai P, Langla S, et al. Survival of Burkholderia pseudomallei and pathogenic Leptospira in cola, beer, energy drinks, and sports drinks. Am J Trop Med Hyg 2020;103:249-252.

In response to reports generating fears of canned beverages contaminated with rat feces and urine leading to human bacterial infection, these authors examined the survival of Leptospira spp. and Burkholderia pseudomallei in canned drinks. Two different species of Leptospira were chosen, in part because these organisms can survive for months in fresh water and soil, and have been linked to contaminated potable water in several countries. In addition, two different strains of Burkholderia pseudomallei (BP) were selected, because this organism is fairly hardy and known to survive for long periods of time in the environment. Studies have shown that BP can survive in normal saline at a pH 2.0 for one day and at a pH 3.0 for up to one week.

Four different beverages were selected, including cola (Coca-Cola original), beer (Singha original), an energy drink (Red Bull Extra), and a sports drink (Gatorade lemon-lime), as well as distilled water for a control. Aliquots of BP and Leptospira at 104 and 108 colony-forming units (CFU)/mL in 0.3 mL sterile water and in EMJH broth, respectively, were inoculated into 2.7 mL of each liquid and kept at 4°C and 37°C. These temperatures are comparable to that for refrigeration and ambient tropical breezes. The spiked beverages were aliquoted and cultured at various intervals for up to four weeks.

Both organisms survived longer at the higher concentrations, although there were significant differences between the survival of the two organisms. The two species of Leptospira survived only briefly in the four beverages (< 15 minutes) at 4°C and less than five minutes at 37°C. But they survived much longer in distilled water at 37°C. In contrast, BP survived for up to four weeks when refrigerated at 4°C in all four canned beverages, and for shorter periods of time in distilled water. However, at 37°C, BP survived for less than three days in beer and Red Bull and less than two hours in Coca-Cola, even at the higher bacterial concentrations. This may be because of the increased acidity of Coca-Cola (pH 2.71) compared to the other beverages (pH range, 3.08-6.49).

Canned beverages could theoretically be contaminated with bacteria during the canning process or in storage if the packaging is disrupted, but most bacteria on the surface of a can will not survive. As with all canned goods, make sure the can is intact before opening. It is not necessary to wash your cans with soap and water, but given the current COVID experience, some compulsive consumers may continue to do so. And, as suggested by the following study report, laboratory inoculations with 108 organisms, such as were used in this experiment, are way beyond the typical scanty bacterial contamination observed in the real world.

‘Hygiene Theater’

SOURCES: Thompson D. Hygiene theater is a huge waste of time. The Atlantic, July 27, 2020.
Goldman E. Exaggerated risk of transmission of COVID-19 by fomites. Lancet Infect Dis 2020;20:892-893.

I received an email from clinic administrators the other day, wondering whether disinfection of the chairs in the clinic waiting room every 30 minutes during COVID was sufficient. Two fabric paintings, gifted by a patient, were removed from the walls, and the magazines in the waiting room were confiscated lest SARS-CoV-2 virus jump off and infect visitors. The New York subway system is spraying seats, walls, and poles with disinfectant. Yet, people are still riding the subway … and standing next to each other. But the pole is clean.

In an immediate notice on May 22, 2020, the Centers for Disease Control and Prevention (CDC) sought to assuage people’s fears that their cereal boxes were not going to infect them by attempting to clarify that although surface contamination resulting in COVID may be possible, most people acquire infection through person-to-person spread.1 Sadly, this statement did not go far enough, and my friend is still washing her store-bought fruits and vegetables with soap and water, my sister lets her groceries sit in the garage for two days before unpacking them, and my neighbor is wearing gloves to get the mail. It reminds me of those televised scenes of the Chinese government spraying disinfectant throughout the city streets during H1N1 in 2009.

This amusing article and a Lancet editorial point out how such actions are completely misguided (hygiene theater), and mistakenly make some people feel safer while obscuring the real risk for infection which is other people. Such activities also waste time, energy, and valuable resources. Your real risk is your friends, family, and co-workers not your mail.

The press has made much about the risk of COVID viral particles surviving for days on surfaces and objects. However, none of the relevant studies are based in realistic scenarios of viral surface contamination or our understanding of respiratory infection. The longest survival of SARS-CoV-2 on surfaces required a large laboratory inoculation of 107 viral particles, and viable virus was found out to six days. Another study applied 106 viral particles to surfaces, and retrieved viable virus four days later. Aerosols spiked with a large inoculum of 105 to 107 of SARS-CoV-2 particles found viable virus on surfaces two days later. But, as the editorialist points out, this would be like 100 people sneezing onto that surface, and then you quickly lick it or rub it in your eye.

In a study where surfaces were contaminated by an actual patient, no viable virus could be found. Similar studies of common community coronavirus found virus survived < 1-3 hours after drying on various surfaces, including surgical gloves and aluminum. People’s fears have been exaggerated by bad science and worse public policy.

Theoretically, high-touch surfaces may pose a risk. Realistically, fomites carrying small amounts of virus that have not been in contact with their owner for > 1-2 hours do not. Ask yourself, how many cases of COVID have been traced to fomites as the cause for infection? As the columnist states, “the extreme infrequency of evidence may indeed be evidence of extreme infrequency.”


  1. Centers for Disease Control and Prevention. CDC updates
    COVID-19 transmission webpage to clarify information about types of spread. Media Statement. May 22, 2020.

Geodynamics of COVID-19 in Brazil

SOURCE: Candido DS, Claro IM, de Jesus JG, et al. Evolution and epidemic spread of SARS-CoV-2 in Brazil. Science 2020; July 23:eabd2161.

Public health measures to reduce the transmission of SARS-CoV-2 virus, such as restrictions on travel and shelter-in-place, may be useful but at a cost. Trying to determine which measures are most useful, and when and where, is important. As of July 12, 2020, Brazil had the second largest number of cases of COVID (> 1.8 million cases), second only to the United States. More than one-third of these cases have occurred in São Paulo, in the southeastern part of the country.

Delays in reporting, changes in reporting requirements, and lack of access to testing sites render a real-time assessment of viral movement throughout the country impossible. Instead, these authors looked to genomics and molecular clock phylogenetics compared with a global data set, which allowed a retrospective estimate of the timing of viral introductions into the country and subsequent movement of virus throughout. Movement of people throughout the country was estimated based on four mobility indices (including a social isolation index from Brazilian geolocation company In Loco, and Google mobility indices for time spent in transit stations, parks, and the average between groceries and pharmacies, retail, and recreational and workspaces).

A total of 26,732 samples obtained from public and private laboratories were tested, identifying 7,944 (29%) SARS-CoV-2 infections. From these, 427 new genomes were constructed, comprising isolates from March 5 to April 30. In addition, 63 Brazilian sequences entered into the GISAID database were included, for a total of 490 sequences. These represented viral genomes from 85 different municipalities across 18 of 27 federal states, and were representative of the outbreak across the country. Only five genomes were found to be lineage B, and the rest were lineage A. The majority of isolates fell into three clades (including clade 1 [38%], clade 2 [34%], and clade 3 [4%]).

Time-based phylogenetic analysis revealed at least 102 introductions of virus into Brazil even before the first cases were recognized. More than half of these were from Italy (26%) and the United States (28%). By the time international travel restrictions were put in place in March, widespread community transmission was occurring already, especially in São Paulo and the southeastern part of the country. Although the introduction of international isolates declined with international travel restrictions, increasing virus transmission, both locally and within state borders, continued to occur.

During the second phase of the epidemic in Brazil, multiple different virus lineages were observed to move outside of large urban areas and the southeastern states to infect other areas within Brazil. This occurred coincident with a 25% observed increase in national travel, especially an increase in longer-distance travel. Nonetheless, within-state travel remained 5.1-fold more frequent than between-state travel.

This interesting study demonstrates how genomics and mobility data can be combined to measure the effect of regional and national travel movement on the evolution of a pandemic throughout a country. Brazil’s efforts to restrict international travel in March were too late; more than 100 different viral lineages had already been introduced into the country, with ongoing increasingly widespread community transmission.