A study today in JAMA Network Open that found quadruple the risk of COVID-19 in California farmworkers reveals risk factors for current or previous SARS-CoV-2 infection in the group, including outdoor work exposures, crowded living conditions, and high body mass index (BMI).
A team led by University of California at Berkeley researchers analyzed the data of 1,107 adult farmworkers undergoing testing for COVID-19 infection and immunoglobulin G (IgG) antibodies at federally qualified community clinics and community sites in the Salinas Valley from Jul 16 to Nov 30, 2020.
Roughly 50,000 farmworkers live in the valley, part of Monterey County, with another 40,000 workers joining their ranks in the peak summer and fall seasons.
Mean worker age was 39.7 years, 52.5% were women, and 79.6% were overweight or obese (BMI of 25 kg/m2 or higher). Of the 1,107 farmworkers, 83.3% were born in Mexico, 63.0% were married or living with a partner, 34.3% traveled to work with non-household members, and 74.5% worked in farm fields on crops such as berries, leafy greens, and broccoli.
Greater risk than any other occupation
The rate of COVID-19 test positivity in farmworkers was four times that of the rest of the county (22% vs 6%). Of 911 workers tested for COVID-19 infection, 118 (13.0%) had positive results, while 201 of 1,058 (19.0%) undergoing antibody testing showed evidence of previous infection.
"In addition, recent studies have shown that agricultural and food workers in California experienced a 39% higher risk of all-cause death from March to October 2020 than during the same period in 2019, a greater increase than any other occupational group; for workers with Latino backgrounds, the increase in all-cause mortality was 60%," the researchers wrote.
In a multivariable analysis that adjusted for recruitment site and enrollment period, the incidence of SARS-CoV-2 infection was higher among workers who worked in the fields (adjusted relative risk [aRR], 1.60) and were exposed to someone with confirmed or suspected COVID-19 infection at home (aRR, 2.98) or at work (aRR, 1.59).
"Whereas indoor exposures are thought to be associated with the greatest risk of transmission, a lower perceived sense of risk during outdoor work or socioeconomic differences between outdoor and indoor workers may contribute to the observed association in our study," the authors wrote.
Positive IgG antibody test results were more common among those living with children 5 years or younger (aRR, 1.40) or unrelated roommates (aRR, 1.40) and among those with a BMI of 30 kg/m2 or higher (aRR, 1.65).
Three quarters (74.9%) of workers lived with children, and 18.6% lived with unrelated roommates. Workers lived with, on average, 5.5 people; 36.5% lived with more than two people per bedroom; 17.9% lived with someone with confirmed or suspected COVID-19 over the course of the pandemic; 10.9% reported being exposed at home in the 2 weeks before coronavirus testing; and 13.5% reported workplace exposures during that timeframe.
Employer interventions tied to lower risk
Nearly all study participants said that their employer provided hand sanitizer, gloves, face coverings, handwashing stations, and information on preventing virus spread at work. But 44.7% said their employer didn't screen them for fever or COVID-19 symptoms on arrival at work.
Workers whose employer gave them information on COVID-19 prevention at work were at 41% lower risk of antibody positivity, and those who were screened for fever or symptoms at work had a 21% lower risk.
The authors noted that essential workers in farming and food production have been disproportionately affected by COVID-19, putting them—as well as the food supply—at risk. In particular, broadly publicized coronavirus outbreaks in food processing plants have highlighted risky working conditions, including unhygienic conditions, poor medical leave policies, and crowded housing.
Most (83%) of farmworkers are Latino, and about a third live in crowded conditions. Farmwork is also a low-paying occupation, with 29% of full-time workers earning a yearly income of less than $26,200 for a family of four, the researchers said.
Measures such as increasing availability of isolation facilities to lower exposure to coronavirus-positive household members and access to paid medical leave to lessen the risk of infection at work may be called for, the authors added.
"These findings suggest that urgent distribution of vaccines to farmworkers and intervention on modifiable risk factors for SARS-CoV-2 infection are warranted given this population's increased risk and the essential nature of their work," they concluded.
Decisions often based on fear
A commentary in the same journal by Sergio Aguilar-Gaxiola, MD, PhD, of the University of California at Davis; Sarah Ramirez, PhD, MPH, of Plazita Pixley; and Edward Kissam of the Werner-Kohnstamm Family Fund, said that interventions should be tailored to mitigate multidirectional virus transmission between homes and workplaces.
"To design effective interventions for community spread, researchers must address the structural factors and social determinants of health faced by farmworkers and other historically underserved populations," they wrote.
Increasing vaccine uptake will require microtargeting, policy changes, and communication strategies that encourage ill farmworkers to seek urgent medical attention rather than reporting to work. In California, nearly 45% of farmworkers lack legal status, less than half have health insurance, and many have never visited a US healthcare facility or don't know that they're at high risk for COVID-19 infection owing to factors such as high BMI.
"In our experience, testing, self-isolation, quarantine, and vaccine uptake are often economically driven decisions based on fear of losing one's precarious employment or income in the event of infection, isolation, or quarantine," Aguilar-Gaxiola and colleagues wrote.