Protecting Workers against
ZIKA
Long Clothing, Repellent among Preventive Measures
BY ROBERT N. PHALEN AND PENGFEI GAO
The association between Zika virus infection during pregnancy and severe birth defects has led to worldwide efforts to prevent more infections. Zika was first identified in 1947, with a geographical distribution primarily in tropical regions of Africa, Southeast Asia and the Pacific Islands. However, since 2015 we have seen the virus spread through South America, Central America, and the Caribbean. Spread to the southern half of the United States is possible, because the Aedes aegpti and Aedes albopictus mosquitoes that can transmit the virus to humans live in these regions as well. In late July 2016, the Florida Department of Health identified an area in one neighborhood of Miami with active transmission of Zika virus. Locally acquired cases have also been reported in the U.S. territories of Puerto Rico, Virgin Islands and American Samoa, as well as neighboring Mexico.
Although most infected people are asymptomatic, the critical issues with Zika infection are with its associated risks, namely severe birth defects and Guillain-Barré syndrome. The primary birth defect is microcephaly, a condition that reduces head size and is a sign of incomplete brain development, which can be accompanied by a host of severe outcomes, such as hearing loss, vision problems, developmental delays and intellectual disability. Guillain-Barré syndrome is an autoimmune disease that attacks the nervous system and can lead to muscle weakness, paralysis, and even death in about 5 percent of those affected. Several countries that have experienced Zika outbreaks recently have reported increases in people who have Guillain-Barré syndrome. This potential relationship is under further investigation by the U.S. Centers for Disease Control and Prevention (CDC). These potential complications of Zika infection are the impetus behind efforts to control and prevent the spread of Zika.
From an occupational health standpoint, industrial hygienists play an important role in protecting workers, their families, and their community from Zika. This is especially true for employees who work outdoors, travel to areas with Zika, or work in the healthcare sector. The focus of this article is on the preventive measures that can be taken by an organization whose workers may be at risk. MODES OF TRANSMISSION Zika virus is an arbovirus (transmitted by arthropods) in the same Flavivirus genus as dengue fever, yellow fever, and West Nile viruses. Mosquito-borne transmission from an infected human to another human is similar to dengue and other similar Flavivirus species. The signs and symptoms of Zika infection are often mild if present at all, and only about 20 percent of infected individuals show any symptoms. Two to seven days following exposure (for example, a mosquito bite), mild fever, a rash, and/or joint pain may be observed. In addition, headache, conjunctivitis (red eyes), and muscle pain may be reported. The symptoms, if any, typically only last up to a week. Thus, Zika infections are largely underreported, facilitating its spread both regionally and worldwide.
Zika virus transmission is primarily associated with the Aedes aegypti and Aedes albopictus mosquitoes. Aedes aegypti and Aedes albopictus bite primarily during the day. These species are most active for approximately two hours after sunrise and several hours before sunset, but they can bite at night in well-lit areas. Aedes aegypti is common to urban tropical areas and many parts of the southern half of the United States. Aedes albopictus, known as the Asian tiger mosquito, is also common to urban areas and similar regions of the U.S., but the potential for transmission of Zika to humans is lower compared to Aedes aegypti
In addition to mosquito-borne transmission to humans, Zika virus can likely be transmitted as a blood-borne pathogen. Zika can also be transmitted sexually from an infected person to his or her partners. Blood transfusions, needle sticks, and contact with blood can transmit the virus. The virus can be found in the blood for about a week after initial infection. Zika remains in semen longer than in blood. Unfortunately, the actual period of communicability is unknown at this time. Lastly, the virus can be transmitted in the blood from a pregnant mother to her fetus, during pregnancy or at delivery. Protecting pregnancies from the devastating impact of Zika virus infection and potential severe outcomes is our primary concern.
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Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers