CDC Travellers Reccomendations by Country:  Mexico

Smart Traveller (diseases you can get overseas)

Infectious Diseases Generally: (see also bacterial, viral and parasitic diseases)

Prions: prions are proteinaceous infectious particles containing, apparently, no genetic material. They are known to cause diseases called transmissible spongiform encephalopathies (TSEs) neurodengerative diseases with long incubation period but rapid progressions once they start. The human TSEs are Creutzfeldt-Jakob isease (CJD). Symptoms of CJD include altered behaviro, demential, memory loss, impaired senses, delirium and prmature senility. The transmissible agent in CJD is a prion. In the late 1990s, it became apparent that humans were contracting a variant form of CJD after ingesting meat form cattle that had been afflicted by bovine sponiform encephalopathy.

Infectious diseases are diseases caused by organisms such as bacteria, viruses, fungi, protozoa or helminths.

Diagnostics/Testing for Infectious Disease:

Biomerieux (has panel testing for infectious disease)

WasteWater Monitoring:

Companies: WasteWater Scan

Wastewater surveillance is used to monitor human shedding of pathogens, including SARS-CoV-2, at a community level and is independent of symptoms, testing access, and care-seeking behavior.See MMWR

During May 12–July 13, 2024, high influenza A virus levels were detected in wastewater in four states, including three states with seasonal human influenza virus activity noted during this time. The H5 subtype was detected in wastewater in nine states; follow-up investigations in many of these states revealed likely animal-related sources, including those related to milk processing. Wastewater samples collected from approximately 750 sites in 48 states and the District of Columbia during May 12–July 13, 2024, were tested for influenza A virus by state and local health departments, a CDC contractor, or an academic partner program (WastewaterSCAN)

Water Safety with respect to Pathogens

Usafe water is responsible for 1.2 million deather per year world-wide. See Our World in Date 1 in 9 people lack access to safe drinking water. See Water Org. Globally, 946 million people still open defecate (9 out of 10 live in rural areas), 2.4 billion people lack access to basic sanitation (7 out of 10 in rural areas), 663 million lack access to basic water sources, and diarrhea is the second leading cause of death in children under five much of which is preventable by clean water and sanitation. See GWPP

The greatest microbial risks are associated with ingestion of water that is contaminated with human or animal feces. Wastewater discharges in fresh waters and costal seawaters are the major source of fecal microorganisms, including pathogens. Microbial waterborne diseases even affect developed countries. In the USA, it has been estimated that each year 560,000 people suffer from severe waterborne diseases, and 7.1 million suffer from a mild to moderate infections, resulting in estimated 12,000 deaths a year. 

Before widespread application of drinking water disinfection treatments, cholera and typhoid were major causes of death in the U.S. 43 million US residents are served by private wells or domestic water systems that are not regulated by the EPA safe drinking water Act, leaving homeowners responsible for maintaining and monitoring water quality in their wells. During 1971-2008, one third of reported disease outbreaks form drinking water were linked to private wells. The complexity of water distribution has also increased; 6 million miles of polumg inside buildins support drinking water, sanitation, hygiene, cooling and heating needs in the US. Premise plumbing water quality can be compromised when water is stagnant or disinfectant concentrations are reduced, thereby promoting microbial pathogen grwoth and biofilm formation. Exposure to biofilm related pathogens can occur thourgh contact with, ingestion of, or aerosol inhalation of contaminated water form different sources, such as showerheads, hot tubs, building cooling towers or decorative fountains. Swimming in untreated recreational water venue (lakes, rivers, and oceans) can cause outbreaks predominantly linked to norovius., Siga toxin-roducing Escherichia coli, Cryptosporidium spp., and Shigella spp. Thsoe enteric pathogens can be introduced into untreated recreational water through human feces or movmit, stormwater runoff, seage or septic system malfunctions or animal waste and can then be transmitted to persons who ingest the contaminated water. See CDC

Bacteria: 

The most important bacterial gastrointestinal diseases transmitted through water are cholera, salmonellosis and shigellosis. These diseases are mainly transmitted through water (and food) contaminated with feces of patients. 

Types bacteria transmitted through water are the following. See Cabral

Campylobacter causes an estimated 1.5 million illnesses each year in the United States. People can get Campylobacter infection by eating raw or undercooked poultry or eating something that touched it. They can also get it from eating other foods, including seafood, meat, and produce, by contact with animals, and by drinking untreated water. Although people with Campylobacter infection usually recover on their own, some need antibiotic treatment. Campylobacter is a gram-negative, microaerophilic genus of bacteria of the family Campylobacteriacae. There are more than 20 species of Campylobacter, not all of which cause human illness. Approximately 90% of human Campylobacter illness is caused by one species, Campylobacter jejuni. Less common species, such as C. coli, C. upsaliensis, C. fetus, and C. lari, can also infect people. See CDC

E. coli strains isolated from intestinal diseases have been grouped into at least six different main groups, based on epidemiological evidence, phenotypic traits, clinical features of the disease and specific virulence factors. From these, enterotoxigenic (ETEC, namely O148), enterohemorrhagic (EHEC, namely O157) and enteroinvasive serotypes (EIEC, namely O124) are of outstanding importance and can be transmitted through contaminated water.

Legionella is the most implicated etiology in public water system outbreaks. Individual or private water system outbreaks assocaited with Legionella resulted in 8% cases, 92% hospitalizaiton and 100% deaths. MMWR, Mark 14, 2024, 73(1) “Surveillance of Waterborne Disease Outbreaks Assocaited with Drinking Water – United States, 2015-2020). 

Pseudomonas aeruginosa lives in the environment and can be spread to people in healthcare settings when they are exposed to water or soil that is contaminated with these germs. Resistant strains of the germ can also spread in healthcare settings from one person to another through contaminated hands, equipment, or surfaces. See CDC

P. aeruginosa is an aerobic gram-negative bacterium and P. aeruginosa is typified by motile, non-spore forming rods that are oxidase positive and lactose nonfermenters. P. aeruginosa is a member of the genus Pseudomonas, colloquially called the pseudomonads. The water-soluble pigments, pyocyanin and pyoverdin, give P. aeruginosa its distinctive blue-green color on solid media. The P. aeruginosa organism thrives in moist environments such as soil and water. It can be found in large numbers on fresh fruits and vegetables. Human colonization begins within the gastrointestinal tract, with subsequent spread to moist cutaneous sites such as the perineum and axilla. It forms smooth fluorescent green colonies at 42oC, with a characteristic sweet (grape-like) odor, making it easy to recognize on solid media in the laboratory. P. aeruginosa is an important plant pathogen, affecting lettuce, tomatoes, and tobacco plants. It can be found in fresh water environments (streams, lakes, and rivers), as well as sinks, showers, respiratory equipment, even contaminating distilled water. See Antimicrobe

P. aeruginosa can cause acute otitis externa (swimmer’s ear), folliculitis (hot tub rash) (1), and painful nodular lesions on the soles or palms (hot hand-foot syndrome) and is likely to be transmitted through contact with contaminated water in pools or hot tubs and not through person-to-person contact. P. aeruginosa is readily inactivated by disinfectants such as chlorine and bromine. Because of this, maintaining a minimum free chlorine concentration of at least 1 ppm in treated recreational water venues open to the public as recommended by CDC prevents waterborne transmission of most pathogens, including P. aeruginosa. Inadequately maintained disinfectant concentration can lead to proliferation of P. aeruginosa and buildup of biofilm on wet venue surface, scale, and sediment. Biofilm is a primarily polysaccharide matrix that is produced by microbial cells and in which bacteria are embedded; biofilm is difficult to remove and cannot be removed by gentle rinsing. Even when adequate disinfectant concentration is maintained, the extracellular matrix of the biofilm can protect P. aeruginosa and other pathogens from disinfectants. Among 987 treated recreational water–associated outbreaks reported to CDC for the period 1971–2021, 369 (37.4%) were linked to a hotel setting (i.e., hotel, motel, lodging, inn, or resort). (see Pseudomonas Infection Outbreak Associated with a Hotel Swimming Pool — Maine, March 2023)

–carbapenemase-producing carbapenem-resistant Pseudomonas aeruginosa (CP-CRPA) infections is challenging because of antibiotic resistance. CP-CRPA infections are highly transmissible in health care settings because they can spread from person to person and from environmental sources. (Cahill)

Vibrio are small, curved-shaped Gram-negative rods, with a single polar flagellum. Vibrios are facultative anaerobes capable of both fermentative and respiratory metabolism. Sodium stimulates growth of all species and is an absolute requirement for most. Most species are oxidase-positive and reduce nitrate to nitrite. Cells of certain species (V. cholerae, V. parahaemolyticus and V. vulnificus) have pili (fimbriae), structures composed of protein TcpA. TcpA formation is co-regulated with cholera toxin expression and is a key determinant of in vivo colonization. The incubation period for cholera is ca. 1–3 days. The disease is characterized by an acute and very intense diarrhea that can exceed one liter per hour. Cholera patients feel thirsty, have muscular pains and general weakness, and show signs of oliguria, hypovolemia, hemoconcentration, followed by anuria. Potassium in blood drops to very low levels. Patients feel lethargic. Finally, circulatory collapse and dehydration with cyanosis occurs. See Cabral

It is common practice in villages in Bangladesh to use cloth, frequently a flat, unfolded piece of an old sari, to filter home-prepared drinks. In laboratory experiments employing electron microscopy, it was found that inexpensive sari cloth, folded four to eight times, provides a filter of ≈20-μm mesh size, small enough to remove all zooplankton, most phytoplankton, and all V. cholerae attached to plankton and particulates >20 μm. Laboratory studies showed that sari cloth folded at least four times retained the V. cholerae cells attached to plankton, effectively removing >99% (>2 logs) of V. cholerae. See Colwell

Vibrio cholerae: (see also bacterial diseases)

Cholera is an acute diarrheal illness caused by infection of the intestine with Vibrio cholerae bacteria. People can get sick when they swallow food or water contaminated with cholera bacteria. The infection is often mild or without symptoms, but can sometimes be severe and life-threatening. About 1 in 10 persons will experience severe symptoms such as profuse watery diahrea, vomitting, thrist, leg cramps and restlessness. People can develop severe dehydration. The profuse diarrhea produced by cholera patients contains large amounts of the infectious Vibrio cholerae germ that can infect others if swallowed. This can happen when the bacteria get on food or into water. Caregivers should wash there hands thoroughly after handling handling feces.  See CDC

The cholera bacterium is usually found in water or in foods that have been contaminated by feces (poop) from a person infected with cholera bacteria. Cholera is most likely to occur and spread in places with inadequate water treatment, poor sanitation, and inadequate hygiene. See CDC

Only toxigenic strains of Vibrio cholerae serogroups O1 and O139 cause epidemics and are reportable as cholera. See Florida Health

Salmonella, a member of the family Enterobacteriaceae, include Gram-negative motile straight rods. Cells are oxidase-negative and catalase-positive, produce gas from D-glucose and utilize citrate as a sole carbon source. Salmonellae have several endotoxins: antigens O, H and V.

CDC estimates Salmonella bacteria cause about 1.35 million infections, 26,500 hospitalizations, and 420 deaths in the United States every year. Food is the source for most of these illnesses. Most people recover without specific treatment and should not take antibiotics. Antibiotics are typically used only to treat people who have severe illness or who are at risk for it.  Salmonella can be found in many foods, including sprouts and other vegetables, eggs, chicken, pork, fruits, and even processed foods, such as nut butters, frozen pot pies, chicken nuggets, and stuffed chicken entrees. Contaminated foods usually look and smell normal, which is why it is important to know how to prevent infection.See CDC

Salmonella is frequently present in surface water, an important source of water for irrigation. An increasing evidence indicates irrigation water as a source (or a vehicle) for transmission of Salmonella. This pathogen can survive in aquatic environments by a number of mechanisms, including entry into the viable but nonculturable (VBNC) state and/or residing within free-living protozoa. As such, assurance of microbial quality of irrigation water is critical to curtail the produce-related foodborne outbreaks and thus enhance the food safety. See Liu

Shigella are Gram-negative, non-sporeforming, non-motile, straight rod-like members of the family Enterobacteriaceae. Cells ferment sugars without gas production. Salicin, adonitol and myo-inositol are not fermented. Cells do not utilize citrate, malonate and acetate as sole carbon source and do not produce H2S. Lysine is not decarboxylated. Cells are oxidase-negative and catalase-positive. Members of the genus have a complex antigenic pattern, and taxonomy is based on their somatic O antigens.

Mycobacterium avium complex (Mac) consists of 28 serovars of two distinct species: Mycobacterium avium and Mycobacterium intracellulare. The importance of Mac organisms was recognized with the discovery of disseminated infection in immunocompromised people, particularly people with HIV and AIDS. Members of MAC are considered opportunistic human pathogens.

Helicobacter pylori has been cited as a major etiologic agent for gastritis and has been implicated in the pathogenesis of peptic and duodenal ulcer disease and gastric carcinoma. However, most individuals that are infected by this pathogen remain asymptomatic

A. hydrophila has gained public health recognition as an opportunistic pathogen. It has been implicated as a potential agent of gastroenteritis, septicemia, meningitis, and wound infections. It can play a significant role in intestinal disorders in children under five years old, the elderly, and immunosuppressed people. 

Viruses:

It is well known that bacteria are major causes of diarrhea transmitted through unsafe drinking water. What is less appreciated are viruses in these same drinking water sources and their impact on human health. Water-transmitted viral pathogens that are classified as having a moderate to high health significance by the World Health Organization (WHO) include adenovirus, astrovirus, hepatitis A and E viruses, rotavirus, norovirus and other caliciviruses, and enteroviruses, including coxsackieviruses and polioviruses. Water treatment utilities routinely assay for the presence of fecal coliforms in water supplies, but they do not assay for the presence of infectious viruses because it is either impossible or not feasible to detect or propagate infectious virus particles in a cost-efficient and timely manner. Despite these barriers, the United States Environmental Protection Agency (USEPA) is evaluating adenovirus, caliciviruses, enteroviruses, and hepatitis A virus for potential regulatory action. See Gall

Hepatitis: Waterborne or foodborne hepatitis caused by hepatitis A virus (HAV) and hepatitis E virus (HEV), has faeco-oral route of transmission. See Dutta 

Polio, or poliomyelitis, is a disabling and life-threatening disease caused by the poliovirus. Paralysis is the most severe symptom associated with polio, because it can lead to permanent disability and death. Between 2 and 10 out of 100 people who have paralysis from poliovirus infection die, because the virus affects the muscles that help them breathe.  Inactivated poliovirus vaccine (IPV) given as an injection in the leg or arm, depending on the patient’s age. Only IPV has been used in the United States since 2000. See CDC

Similar to other non-polio enteroviruses (NPEVs), PV is transmitted via the fecal-oral route and efficiently replicates in the intestinal tract. During PV infection, the virus is excreted from the human gut into the stool for ∼2 months. Although most PV infections are asymptomatic, patients can develop poliomyelitis following viremia in some cases, resulting in residual paralysis. Since the live oral poliovirus vaccine (OPV) was introduced in many industrial countries in the 1960s, polio epidemics have been successfully controlled. In 1988, the World Health Assembly resolved to eradicate polio by launching the Global Polio Eradication Initiative (GPEI). Large-scale OPV immunization resulted in a drastic reduction in the number of poliomyelitis cases. To date, the only countries where polio is endemic are Nigeria, Pakistan, and Afghanistan. See Yoshida

Diagnosis is usually based on repeated stool examinations but examination of duodenal fluid or biopsy material may also be necessary. Enzyme immunoassay or indirect immunofluorescence methods for direct detection of antigen or whole organisms in clinical specimens have also been developed. These tests are reported to be more sensitive than routine stool examination. See Wolfe

Protozoa:

Giardia: Giardiasis has a global distribution and it is a common cause of diarrhea in both children and adults and is transmitted via the fecal-oral route through direct or indirect ingestion of cysts. The laboratory diagnosis of Giardia spp. is mainly based on demonstration of microscopic cyst or trophozoite in stool samples but several immunological-based assays and molecular methods are also available for giardiasis diagnosis.  See Delavari Healthcare providers can order laboratory tests to identify Giardia germs in the stool (poop) of someone who is sick. Sometimes it can be difficult for doctors to know for sure if Giardia is making you sick. This is because people with a Giardia infection do not pass Giardia germs with every stool. Even when there are Giardia germs in their stool, there may not be enough for the laboratory to find and identify them. See CDC

Cryptosporidium parvum and Cryptosporidium hominis are obligate enteric protozoan parasites which infect the gastrointestinal tract of animals and humans. The mechanism(s) by which these parasites cause gastrointestinal distress in their hosts is not well understood. The risk of waterborne transmission of Cryptosporidium is a serious global issue in drinking water safety. Oocysts from these organisms are extremely robust, prevalent in source water supplies and capable of surviving in the environment for extended periods of time. Resistance to conventional water treatment by chlorination, lack of correlation with biological indicator microorganisms and the absence of adequate methods to detect the presence of infectious oocysts necessitates the development of consistent and effective means of parasite removal from the water supply. see Carey

–Transmission: Cryptosporidium parasites get into surface water sources, such as rivers and lakes, from the stool (feces) of infected animals or people. Public water systems that get their water from these surface water sources can contain Cryptosporidium oocysts (the egg-like form of the parasite). Filtration treatment will usually remove Cryptosporidium oocysts. Chlorine disinfection by itself is not effective. All Virginia public water systems that use surface water sources provide filtration treatment. In addition, in an effort to reduce health risks associated with Cryptosporidium, the Environmental Protection Agency (EPA) has promulgated the Long Term 2 Enhanced Surface Water Treatment Rule (LT2). LT2 requires that all water systems that obtain their water from surface water sources must monitor the raw (source) water for Cryptosporidium oocysts or indicator organisms. Monitoring results will indicate whether systems will be required to provide additional treatment to achieve effective Cryptosporidium reduction. See Virgina Department of Health

—-Recreational Water:

Recreational water can be classified as treated or untreated. Treated recreational water undergoes systematic treatment (e.g., disinfection or filtration) to maintain quality for recreational use and is typically in an enclosed and manufactured structure. In addition to pools and hot tubs, splash pads are treated recreational water venues. Splash pads can include single-pass splash pads in which treated tap water is circulated but does not undergo additional treatment within the splash pad. Untreated recreational water does not undergo systematic treatment to maintain quality for recreational use. Lakes, rivers, and oceans are untreated recreational water venues.

——Splash pads: Splash pads, also known as water playgrounds, interactive fountains, spray pads, spray parks, and wet decks, spray or jet water on users. Water can either be recirculated or pass once through the venue plumbing. In recirculating splash pads, after being sprayed or jetted, the water drains into a tank and is filtered and disinfected before being sprayed or jetted again. In single-pass splash pads, water circulates through the plumbing only once before draining, typically into a sewer system. During 1997–2022, public health officials from 23 states and Puerto Rico reported 60 waterborne disease outbreaks associated with splash pads. These reported outbreaks resulted in 10,611 cases, 152 hospitalizations, 99 emergency department visits, and no reported deaths. The 40 (67%) outbreaks confirmed to be caused, in part, by Cryptosporidium resulted in 9,622 (91%) cases and 123 (81%) hospitalizations. Two outbreaks suspected to be caused by norovirus resulted in 72 (73%) emergency department visits. See CDC

Cryptosporidium oocysts are common and widespread in ambient water and can persist for months in this environment. The dose that can infect humans is low, and a number of waterborne disease outbreaks caused by this protozoan have occurred in the United States, most notably in Milwaukee, Wisconsin, where an estimated 400,000 people became ill in 1993. See EPA

–Disinfection Measures: Even the lowest concentration of ammonia decreased significantly the viability of oocysts after 24 h of exposure. Increasing concentrations of ammonia increased inactivation rates, which ranged from 0.014 to 0.066 h−1. At the highest concentration of ammonia, a small fraction of viable oocysts still remained. Exposure to pH levels corresponding to those associated with the ammonia concentrations showed minimal effects of alkaline pH alone on oocyst viability. See Jenkins

Cyclosporiasis is infection with the protozoan Cyclospora cayetanensis. Symptoms include watery diarrhea with gastrointestinal and systemic symptoms. Diagnosis is by detection of characteristic oocysts in stool or intestinal biopsy specimens. Cyclosporiasis is caused by an obligate intracellular coccidian protozoa. Transmission is by the fecal-oral route via contaminated food or water. Cyclosporiasis has not yet been associated with commercially canned or frozen foods. This infection is most common in tropical and subtropical climates where sanitation is poor. Residents and travelers to endemic areas are at risk. Early reports of Cyclospora cayetanensis outbreaks in the US were attributed to imported raspberries from Guatemala. Subsequently, outbreaks of C. cayetanensis infection have followed ingestion of contaminated fresh vegetables including basil, snow peas, mesclun lettuce, and cilantro. In the summer of 2013, a multi-state outbreak involving hundreds of people in the US was attributed to ingestion of prewashed salad mixes  A 2018 multi-state outbreak was attributed to contaminated fresh vegetable trays. The life cycle of C. cayetanensis is similar to that of Cryptosporidium Crexcept that oocysts passed in stool are not sporulated. Thus, when freshly passed in stools, the oocysts are not infective, and direct fecal-oral transmission cannot occur. The oocysts require days to weeks in the environment to sporulate and, therefore, direct person-to-person transmission is unlikely. The sporulated oocysts are ingested in contaminated food or water and excyst in the gastrointestinal tract, releasing sporozoites. The sporozoites invade the epithelial cells of the small intestine, replicate, and mature into oocysts, which are shed in stool. See Merk Manual