Flesh-eating screwworms feast on humans in Mexico; human cases top 500

食肉螺旋蝇在墨西哥肆虐，人类感染病例突破 500 例

Since the flesh-eating screwworm fly reinvaded Mexico in 2024, human cases of the voracious parasite have been mounting. According to a July surveillance report from Mexico’s Ministry of Health, there have been over 500 human cases in 2025 and 2026. 自 2024 年食肉螺旋蝇再次入侵墨西哥以来，这种贪婪寄生虫导致的人类感染病例一直在增加。根据墨西哥卫生部 7 月份的监测报告，2025 年和 2026 年已累计出现超过 500 例人类感染病例。

A study this week in the journal Emerging Infectious Diseases analyzed the information on over 200 confirmed cases reported between April 2025 and March 2026 and found that the infestation pace is increasing. Among the 200 confirmed cases in the study, six deaths were reported. At least one of the deaths was directly caused by the fly’s maggots, researchers in Mexico reported in the study. 本周发表在《新发传染病》（Emerging Infectious Diseases）期刊上的一项研究分析了 2025 年 4 月至 2026 年 3 月间报告的 200 多例确诊病例，发现感染速度正在加快。在研究涉及的 200 例确诊病例中，有 6 例死亡报告。墨西哥研究人员在研究中指出，其中至少有一例死亡是直接由该蝇类的蛆虫引起的。

The New World screwworm (NWS) fly was once endemic in Mexico—as well as the US. The flies lay hundreds of eggs in the wounds, inflamed tissue, mucous membranes, and orifices of warm-blooded creatures. The resulting maggots hatch within a day and begin ravenously feasting on the living flesh of their victims. While the fly’s maggots generate ghastly, life-threatening wounds in a variety of warm-blooded species, including humans, they’re particularly devastating to livestock. 新世界螺旋蝇（NWS）曾是墨西哥和美国的地方性物种。这种蝇类会在温血动物的伤口、发炎组织、粘膜和孔窍中产下数百枚卵。孵化出的蛆虫在一天内就会开始贪婪地啃食受害者的活体组织。虽然这些蛆虫会在包括人类在内的多种温血动物身上造成可怕且危及生命的伤口，但它们对牲畜的破坏尤为严重。

Amid a decades-long eradication effort, the fly’s populations were wiped out from the US, Mexico, and Central America. This was largely done with massive aerial releases of sterilized male flies, a technique that works because female NWS flies only mate once in their lifespans. Mexico declared NWS eradicated in 2003. Panama declared eradication in 2006 and kept an active, biological barrier along the Darién Gap at the border with Colombia. But in 2022, the barrier was breached, and Mexico began seeing cases in animals in 2024. 经过数十年的根除努力，该蝇类种群曾在美国、墨西哥和中美洲被彻底消灭。这主要归功于大规模空中投放绝育雄蝇，该技术之所以有效，是因为雌性新世界螺旋蝇一生只交配一次。墨西哥于 2003 年宣布根除该物种。巴拿马于 2006 年宣布根除，并在与哥伦比亚交界的达连地峡（Darién Gap）沿线保持着有效的生物屏障。然而，2022 年该屏障被突破，墨西哥于 2024 年开始出现动物感染病例。

Mexico’s cases

墨西哥的病例

Since the breach, there have been more than 36,000 animal cases of NWS in Mexico, with nearly 2,000 active as of August 5, according to the US Department of Agriculture. While human NWS infections—called myiasis—are a small fraction of the overall cases, the infestations can be severe and horrifying. The maggots can cause painful, rapidly enlarging deep wounds, which can destroy muscle, cartilage, and bone—even the skull—if not caught quickly. The wounds pose the risk of irreparable damage, secondary infection, sepsis, and, in extreme cases, death. 据美国农业部统计，自屏障被突破以来，墨西哥已发生超过 36,000 例动物感染病例，截至 8 月 5 日，仍有近 2,000 例活跃病例。虽然人类感染新世界螺旋蝇（称为蝇蛆病）在总病例中占比很小，但感染情况可能非常严重且骇人。如果不及时发现，蛆虫会导致疼痛且迅速扩大的深层伤口，破坏肌肉、软骨和骨骼，甚至颅骨。这些伤口存在造成不可逆损伤、继发感染、败血症的风险，极端情况下甚至会导致死亡。

To better understand the human health impact of NWS’s reemergence in Mexico, researchers surveyed public health, epidemiological, and laboratory reports of confirmed NWS myiasis cases between April 2025 and March 2026. In 2025, the cases were being reported at a rate of about three per week. But in 2026, the pace increased to just over nine a week. The study identified 204 cases in all, but two did not have sufficient data to be included in the analysis. Of the 202 remaining cases, researchers found 145 (72 percent) were in male patients. 为了更好地了解新世界螺旋蝇在墨西哥卷土重来对人类健康的影响，研究人员调查了 2025 年 4 月至 2026 年 3 月间确诊的蝇蛆病病例的公共卫生、流行病学和实验室报告。2025 年，病例报告速度约为每周 3 例。但到了 2026 年，这一速度增加到每周 9 例以上。研究共识别出 204 例病例，但其中 2 例因数据不足未被纳入分析。在剩余的 202 例病例中，研究人员发现 145 例（72%）为男性患者。

The age of fly victims ranged from 12 to 93 years, but skewed toward older adults, with a mean of 61. Most of the myiasis cases (77 percent) were in patients with one or more underlying health conditions, most commonly diabetes, alcoholism, cancers, and skin conditions. When the flies infect humans, they seem to have the most success infesting the legs and feet, the study found; More than half (55 percent) of cases were in the lower limbs. But the flies are not picky. The next most common sites were reported as the head/neck, including the nose, mouth, and eyes. Fewer cases were seen in the upper limbs, trunk, ear, genitalia, and abdominal cavity. 受害者年龄在 12 岁至 93 岁之间，但以老年人居多，平均年龄为 61 岁。大多数蝇蛆病患者（77%）患有一种或多种基础疾病，最常见的是糖尿病、酗酒、癌症和皮肤病。研究发现，当蝇类感染人类时，腿部和足部似乎最容易受害；超过一半（55%）的病例发生在下肢。但这些蝇类并不挑剔，其次最常见的感染部位是头部/颈部，包括鼻子、嘴巴和眼睛。上肢、躯干、耳朵、生殖器和腹腔的病例较少。

Six deaths were reported among patients with confirmed NWS myiasis, but it’s unclear in most of the cases how much the infestation contributed to the deaths. Only one had NWS myiasis listed as the cause of the death. The other deaths were in patients with cancers, encephalitis, respiratory failure, and septic shock. The average age of patients with NWS-linked deaths was 79.5 years. 在确诊的蝇蛆病患者中，有 6 例死亡报告，但在大多数病例中，尚不清楚感染在多大程度上导致了死亡。只有 1 例将蝇蛆病列为直接死因。其他死亡病例涉及癌症、脑炎、呼吸衰竭和感染性休克患者。与新世界螺旋蝇相关的死亡患者平均年龄为 79.5 岁。

One Health approach

“全健康”（One Health）方针

The geographic distribution of the human cases unsurprisingly mirrored the distribution of reported animal cases. But it remains unclear why men seem to be at higher risk of the flesh-eating maggots. They speculated that occupational exposure, outdoor activities, contact with animals, unattended wounds, or delayed healthcare seeking could be factors in the imbalance. 人类病例的地理分布与报告的动物病例分布如出一辙，这并不令人意外。但目前尚不清楚为什么男性似乎面临更高的食肉蛆感染风险。研究人员推测，职业暴露、户外活动、与动物接触、伤口未得到护理或延迟就医可能是导致这种差异的因素。

Overall, the researchers conclude that the cases highlight an important link between human and animal health. “Because animal and human cases reflect northward spread of the NWS fly and that spread is expected to continue, surveillance, diagnostic preparedness, animal movement controls, and fly-suppression activities should be implemented proactively at the leading edge of expansion, rather than only after human cases are detected,” the researchers write. “Coordination between human health, animal health, wildlife, and agricultural sectors will be essential to guide prevention and control measures.” 总的来说，研究人员得出结论，这些病例凸显了人类健康与动物健康之间的重要联系。研究人员写道：“由于动物和人类病例反映了新世界螺旋蝇向北扩散的趋势，且预计这种扩散将持续下去，因此应在扩散的前沿地带主动实施监测、诊断准备、动物流动控制和灭蝇活动，而不是等到发现人类病例后再采取行动。人类健康、动物健康、野生动物和农业部门之间的协调对于指导预防和控制措施至关重要。”

The US reported its first animal cases in Texas in June amid the reemergence. Since then, the USDA has reported 45 animal cases. So far, no human NWS myiasis cases have been reported in the US from the fly’s resurgence. But there have been travel-related cases amid the reemergence in Central America and from people returning from other locations with endemic NWS populations. 随着新世界螺旋蝇的卷土重来，美国于 6 月在德克萨斯州报告了首批动物感染病例。自那时起，美国农业部已报告了 45 例动物病例。到目前为止，美国尚未报告因该蝇类复发而导致的人类蝇蛆病病例。但在中美洲的复发期间，以及从其他存在新世界螺旋蝇地方性种群的地区返回的人员中，已出现与旅行相关的病例。