The first confirmed case of COVID-19 in Mexico was reported on February 27, 2020 (1). About a month later, when the number of confirmed cases in the country had surged to 848 (2), the Mexican federal government launched the “National Healthy Distance” campaign (3). This campaign urged people to wash their hands frequently, practice social distancing, and, if possible, work from home. On March 30, 2020, the federal government declared a national health emergency and suspended all non-essential activities (4). Farmworkers were among the occupational groups deemed essential to the economy (5) and continued in-person work. On June 1, 2020, with no clear signs that transmission had been brought under control, the federal government introduced a “traffic light” alert system for epidemiological risk in each state, guiding state responses and replacing nationwide suspensions (6). In August 2020, Mexico ranked among the top 10 countries in terms of infections and the top five in terms of deaths per 100,000 inhabitants (7). The COVID-19 vaccination campaign, led by the Mexican federal government, began on December 24, 2020, prioritizing healthcare workers, teachers, and adults aged over 60 years (8).

Approximately 21% of Mexico’s population resides in rural areas (9), with 12% employed in the agricultural sector (10). Both farmworkers and non-farmworkers living in rural areas face similar poverty indicators, such as educational attainment, income level, food access, housing quality, and healthcare accessibility (11). The COVID-19 pandemic has exacerbated long-standing socioeconomic and health disparities in historically underserved populations in Mexico (12–15) and worldwide (16, 17), including those living in rural areas. One of the most glaring disparities highlighted by the COVID-19 pandemic was the limited access to healthcare in rural areas, where about one in four people has access to adequate facilities (18). This lack of healthcare infrastructure made it exceedingly difficult for individuals in the rural areas to receive prompt medical attention and SARS-CoV-2 testing, thereby exacerbating virus spread and increasing the risk of severe illness or death. Moreover, poverty remains more prevalent in rural areas (19), introducing additional risk factors for SARS-CoV-2 infection like malnutrition and overcrowded housing. Despite the availability of COVID-19 vaccines to non-healthcare professionals in Mexico since February 2021, vaccine hesitancy is slightly more prevalent among rural and indigenous communities (20). This hesitancy often stems from limited access to reliable information, historical distrust of healthcare systems, and misinformation, contributing to lower vaccination rates in these populations (21).

Epidemiological studies conducted in the United States (22–26) and Europe (27, 28) have shown that farmworkers are among the populations disproportionately affected by the COVID-19 pandemic. However, little is known about the burden among farmworkers in Mexico and other low- and middle- income countries (LMICs). Recently, a study of banana farmworkers in Guatemala conducted from June 2020 to October 2021 (29) found a SARS-CoV-2 infection prevalence (3.1 cases/100 person-years) similar to the one reported in a study of primarily Mexican-born and low-income farmworkers from California conducted from July to November 2020 (22). The latter study found that some of the risk factors for SARS-CoV-2 infection among farmworkers were low educational attainment, living in crowded housing or with unrelated roommates, living in urban areas, and working in the fields (or outdoors) rather than elsewhere in agriculture (30). Farmworkers in Mexico, while having different living and working conditions from those in the U.S. and Europe, likely share commonalities in various structural factors and social determinants of health, such as limited healthcare access, economic vulnerability, and labor rights (31, 32). These shared factors could potentially increase Mexican farmworkers’ risk for SARS-CoV-2 infection and the negative impact of the COVID-19 pandemic on their lives. Notably, the study of farmworkers in Guatemala observed that those who experienced COVID-19 had greater disease severity, absenteeism, and economic losses than farmworkers with other influenza-like illnesses (29). Likewise, recent cross-sectional studies of primarily Mexican-born farmworkers in California and Washington State found that the COVID-19 pandemic exacerbated challenges affecting mental health and food security among this vulnerable population (33–35).

Mexico is the world’s largest producer of avocados (36), accounting for 45% of global production (37). As of 2022, the state of Michoacan produced approximately 72% of the nation’s avocados (37) and was home to around 34,000 avocado farmers (38). Michoacan has a population of 4.7 million people, with about 30% residing in rural areas (39). The state has played a crucial role in the dynamics of agricultural labor migration to the U.S. (40). For instance, between 2015 and 2020, Michoacan ranked third among the 32 Mexican states in the number of immigrants to the United States, with nearly 40,000 immigrants (41). Due to the state’s heavy reliance on agriculture and its substantial rural population, understanding the impact of the COVID-19 pandemic on its residents, especially those employed in the avocado industry, holds significant importance. This study aimed to assess the prevalence of SARS-CoV-2 infection among Michoacan avocado farmworkers in May 2021. Additionally, it examined sociodemographic, household, community, and workplace factors associated with prior SARS-CoV-2 infection (as indicated by immunoglobulin G (IgG) seropositivity) among unvaccinated farmworkers. Lastly, the study delved into evaluating the mental health and economic impact of the COVID-19 pandemic on both unvaccinated and vaccinated farmworkers.

Most study participants were male (97.7%), were married or living as married (76.5%), lived in Tingambato (61.3%), and reported annual household earnings of less than $6,000 per year (66.6%) (Table 1), which was similar to the mean annual household income in rural Michoacan in 2020 (USD $5,800), but lower than the mean in 2022 (USD $7,000) (57). Participants had a median age of 37 years (interquartile range (IQR) 28–48) and lived with a median of 3 household members (IQR 2–5). Approximately half had completed middle school or had lower levels of education (56.4%), lived with other farmworkers (53.2%), and lacked health insurance (50.4%) (Table 1). Around three-quarters (77.5%) were overweight or obese, while a small percentage reported having diabetes (5.3%) or hypertension (11.1%). Notably, 61% of all participants reported experiencing symptoms indicative of SARS-CoV-2 infection since March 2020, yet only 3.8% had tested positive for COVID-19 (Table 1). Among farmworkers who experienced symptoms, approximately 40% continued working despite being symptomatic, while those who stayed home due to symptoms missed an average of 7.0 (SD 13.0) workdays.

At the time of the interview, 85.1% farmworkers were unvaccinated and, among these, 33.3% tested IgG positive (Table 2). Among the 56 (14.9%) participants who were partially or fully vaccinated, 87.5% tested IgG positive. Vaccinated farmworkers were older (mean age of 54.1 (SD 14.9) years) and more educated (50% had completed a bachelor’s degree or technical studies) compared to unvaccinated farmworkers (36.4 (12.3) years; and 13.7%, respectively) (Table 1). Additionally, vaccinated participants were more likely to be married or living as married (87.5%), reside in Tingambato (75.0%) or Uruapan (19.6%), and report household earnings greater than $6,000 per year (33.9%) compared to unvaccinated farmworkers (75, 67, 12.5%; respectively) (Table 1).

In this study of avocado farmworkers in Michoacan, no participants tested positive for current SARS-CoV-2 infection in May 2021, while 33% of unvaccinated farmworkers showed evidence of past infection (positive for IgG against SARS-CoV-2). This seroprevalence is slightly higher than the 25% noted among Guatemalan farmworkers from June 2020 to October 2021 (period that encompasses the first and second nationwide waves of new COVID-19 cases) (29), but well below the 53% observed among migrants in Tijuana, Mexico, from November 2020 to April 2021 (period that encompasses Baja California’s second wave of new COVID-19 cases) (58). Differences in SARS-CoV-2 seroprevalence between studies and populations must be interpreted with caution because of variations in timing of data collection, screening approaches, and between-country heterogeneity (59). Differences in routes of SARS-CoV-2 exposure could also play a role in the variability of seroprevalence estimates across studies.

In our study, we found that unvaccinated farmworkers who lived with other farmworkers, lived in more urban areas, and who had ever lived with someone with COVID-19 had a higher prevalence of IgG-positive SARS-CoV-2 infection. Similar findings, supporting the now well-established fact that household exposures substantially increase the risk of SARS-CoV-2 infection (33), were observed in a cross-sectional study of predominantly Mexican-born and low-income farmworkers in California (22). In Michoacan, we also found that farmworkers who cooked with a wood-burning stove had a lower risk of IgG positivity. This finding is unexpected, given previous research indicating that poor indoor air quality, particularly from indoor sources of air pollution such as cooking, may increase the risk of COVID-19 transmission and mortality (60). Nonetheless, it is possible that farmworkers with wood-burning stoves had better ventilation in their houses, built their stoves outside their houses, or spent more time outside than those with other stove types. We observed that livelihood with children under age 5 was associated with a higher seropositivity prevalence in our bivariate, but not multivariate, analyses. Mexico experienced one of the longest school closures globally due to the COVID-19 pandemic, lasting nearly 250 days from March to August 2020 (61). As farmworkers continued to work in-person during the pandemic, it is likely that their children had to be cared for by grandparents or other relatives while schools were closed, potentially exposing them to SARS-CoV-2 in environments other that their own.

Consistent with findings from other studies (30, 58, 62, 63), we observed an increased risk of IgG positivity among individuals with self-reported diabetes. However, only 3.3% of unvaccinated farmworkers in our study reported this medical condition, so this association must be interpreted with caution. The observed diabetes prevalence is lower than the 11.4% observed among primarily Mexican-born California farmworkers (30) and the 15.7% observed among the general Mexican population (21). Differences in diabetes prevalence could be partly explained by our exclusion of vaccinated farmworkers, among whom 17.9% reported diabetes and who were, on average, older (mean (SD): 54.1 (14.9) years) than those unvaccinated (36.4 (12.3) years). Nevertheless, differences could also be due to the significant proportion of unvaccinated farmworkers who lacked health insurance (54.6%) and might have undiagnosed medical conditions, such as diabetes. The mechanisms that explain the increased risk of SARS-CoV-2 infection and severity of COVID-19 among individuals with diabetes, including oxidative stress and the release of pro-inflammatory cytokines, have been widely documented (62, 64).

We observed that the impact of the COVID-19 pandemic among avocado farmworkers extended beyond infection. For example, 66% of farmworkers reported that their lives had been negatively affected by the pandemic. Notably, only a small number of participants reported depression (9%) and anxiety (11%) symptoms in the 2 weeks preceding the time of interview, which is lower than the prevalence reported in other Mexican populations since the COVID-19 pandemic started (65, 66). However, it is possible that farmworkers may have underreported their anxiety and depression symptoms (67, 68). We also observed that the COVID-19 pandemic had a substantial economic impact among vaccinated and unvaccinated farmworkers, as indicated by their reduced ability to pay bills and food insecurity. The prevalence of food insecurity among Michoacan farmworkers (27%) is lower than the 37% observed among California farmworkers in November 2020 (33). The proportion of Michoacan farmworkers who experienced more difficulties paying bills since the COVID-19 pandemic started (29%) is in line with the 28% observed among California farmworkers in November 2020 (33), but much lower than the 62% noted in a statewide study of farmworkers in California conducted between July 2021 and April 2022 (34). Nonetheless, it is essential to recognize that comparing the experiences of farmworkers across multiple countries may not provide a reliable basis for assessment due to the significant differences in their socio-economic conditions, healthcare systems, and governmental support mechanisms.

To our knowledge, our study is the first to determine the prevalence of SARS-CoV-2 infection among Mexican farmworkers and to examine the impact of the COVID-19 pandemic in this vulnerable population. However, several limitations should be considered. Our analysis is cross-sectional, and our sample size is modest but consistent with figures from studies in other countries (27, 69, 70). In addition, our sample was not random, which limits the generalizability of our results to the larger Mexican farmworker population and rural communities. Moreover, waning antibodies, especially among individuals who experienced mild or asymptomatic infection, may have contributed to misclassification in IgG positivity for individuals infected early in the COVID-19 pandemic (71–73). Finally, our survey was self-administered, which may have led to incomplete or inaccurate data, particularly among farmworkers with lower educational levels.

Our findings indicate that avocado farmworkers in Michoacan have been significantly affected by the COVID-19 pandemic, both in terms of morbidity and its economic impact on their lives. Given farmworkers’ risk of repeated SARS-CoV-2 infections due to their living conditions, poor access to health care, and high prevalence of comorbidities (e.g., obesity, diabetes) that increase the risk of severe COVID-19 and long COVID (74, 75), a multi-faceted approach is required to address their unique needs and challenges. Potential strategies for supporting farmworkers may include increasing their access to healthcare (e.g., expanding telemedicine options and mobile clinics) and providing financial and mental health support, especially for farmworkers who are unable to work due to COVID-19 or long COVID symptoms.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving humans were approved by the Institutional Review Boards at University of California, Berkeley and Escuela Nacional de Estudios Superiores Unidad Morelia, Universidad Nacional Autónoma de México (UNAM). The participants provided their written informed consent to participate in this study.

CA-A and AM had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. CA-A, MT-O, FC, AS-V, JD, BE, and AM: concept and design. CA-A, MT-O, FM-A, MR-B, DB-S, FC, AS-V, DL-C, JD, BE, and AM: acquisition, analysis, or interpretation of data. CA-A, MT-O, and AM: drafting of the manuscript. CA-A, MT-O, FM-A, MR-B, DB-S, FC, AS-V, DL-C, JD, BE, and AM: critical revision of the manuscript for important intellectual content. CA-A, FM-A, and AM: statistical analysis. CA-A, FC, AS-V, DL-C, JD, BE, and AM: obtained funding. CA-A, MT-O, MR-B, DB-S, BE, and AM: administrative, technical, or material support. CA-A and AM: supervision. All authors contributed to the article and approved the submitted version.