Myanmar uses a traditional method of elephant logging for timber harvest. Consequently, Myanmar has a large network of communities in which loggers live together in temporary villages with their families and occasionally migrant laborers. We collected data from 102 healthy persons from 5 elephant logging communities in and near the Yenwe Forest Reserve, a protected area in central Myanmar, during June 2016–August 2018. Most (57/102) participants, including persons from forest management, logging crews, and elephant caretakers, worked in the protected area and were exposed to forested areas and vectors associated with CCHFV (Table 1). Participants were 17–67 years of age and the median age was 32.5 years. We collected venous blood samples and quantitative medical and behavioral questionnaires from each participant (Appendix).

We used a bead-based MagPix (Luminex Corporation, https://www.luminexcorp.com) assay platform, developed at the US Army Medical Research Institute of Infectious Diseases, to detect specific IgG reactivity against the nucleoprotein of CCHFV. We used molecular detection of conserved regions of the small, medium, and large segments of bunyavirus to detect CCHFV viremia with conventional PCR (Appendix).

We identified previous CCHFV exposure among study participants, but we did not detect any active infections. Study participants did not exhibit any signs of hemorrhagic fever, and none reported having previously suffered symptoms of hemorrhagic-like illnesses. All participants tested negative for bunyaviruses by consensus PCR. Among study participants, 9.8% (10/102) were seropositive for CCHFV by MagPix IgG assay. Samples categorized as positive ranged from 1,124–8,911 mean fold increase (MFI) and a signal-to-noise ratio (S/N) of 33.8–207.8. Negative samples had an MFI of 44–854 and 1–19.9 S/N. Persons 31–40 years of age were significantly more likely to be seropositive for CCHFV (p = 0.05) compared with other age groups. We noted no statistically significant associations between specific occupations and CCHFV exposure (Table 1).

Persons who reported handling live or recently slaughtered primates (age-adjusted odds ratio [OR_{age adjusted}] = 5.53; p = 0.020) or wild carnivores (OR_{age adjusted} = 1.3; p = 0.004) in their lifetimes were more likely to have been exposed to CCHFV (Table 2). Handling primates was significantly correlated with handling carnivores (Pearson’s correlation = 0.6; p<0.001). Therefore, we used independent multivariable logistic regression models to adjust for age while assessing the association of CCHFV seropositivity for these 2 factors. More male than female persons reported handling primates (20 male vs. 3 female persons) and carnivores (9 male vs. 3 female persons) and their ages ranged from 19–60 years. Handling primates or carnivores was not statistically significantly associated with any occupational or other behavioral factors.

Among persons who reported handling wildlife, the highest risk species for CCHFV exposure were primates and carnivores. Although sample size for handling some live or recently slaughtered wild animal taxa were low (for instance, <5 persons each reported handling rodents or bats), we found no statistically significant association between combined wildlife taxa evaluated and CCHFV exposure (p = 1.0; Table 2).

A bite from an infected tick was not the likely route of exposure to CCHFV in this community. We evaluated occupations associated with increased forest contact, and thus tick habitat, such as resource extraction, protected area worker (forest ranger), or hunter, as a combined variable, but we found no statistically significant association between occupation and CCHFV exposure.

Contact with domestic animals also was not the likely route of CCHFV exposure in this community. Study participants were not frequently exposed to ruminants, the domestic animal group most reported as associated with CCHFV exposure in endemic countries. Participants were more likely to report contact with pigs or poultry, but these animals have not been identified as amplifying hosts for CCHFV. Contact with live or dead domestic animals of any kind was not associated with CCHFV exposure (Table 2).

Nonhuman primates have not been implicated as natural reservoir hosts or sources of human CCHFV infection. However, rhesus macaques (Macaca mulatta) and long-tailed macaques (M. fascicularis), which range throughout Myanmar, have been infected with CCHFV in laboratory settings. Rhesus macaques develop viremia without clinical signs, but long-tailed macaques develop signs of clinical illness and viremia similar to disease progression in humans (15). Contact with blood or other bodily fluids, including saliva, urine, or feces, during a period of viremia in macaques could lead to human infection. Similarly, wild carnivores have not been implicated as natural reservoir hosts for CCHFV, but red foxes (Vulpes vulpes), which are thought to range in Myanmar, and Pallas’s cats (Otocolobus manul), which range in central Asia, have demonstrated CCHFV seropositivity and could serve as sources of human infection, particularly through bushmeat hunting, which exposes persons to animal blood and body fluids.

Our findings indicate that CCHFV is circulating in Myanmar with human infections that are either mildly symptomatic or occurring in populations that fall outside of existing surveillance systems. Although exposure to domestic animal amplifying hosts is the most commonly reported exposure type for human CCHFV infections in endemic countries, our findings show that persons with close contact with wild animal reservoir hosts, especially blood and body fluids of nonhuman primates and carnivores, also are at risk for CCHFV infection. Surveillance of at-risk populations in Myanmar should be expanded to better prepare for potential future outbreaks of CCHF.

Additional information on Crimean-Congo hemorrhagic fever virus in logging communities, Myanmar.