DDP Newsletter May 2018 Vol. XXXIV, No. 3
Deadly diseases once thought to be controlled are re-emerging globally, invading or re-invading new territory. The number of infectious disease outbreaks worldwide and in the U.S. has steadily increased, from fewer than 1,000 in a 5-year period 1980-1984 to more than 3,000 in 2005-2009. Human-specific diseases, zoonoses such as Salmonella, vector-borne and non-vector-borne infections have all increased.
Rapid urbanization, travel, mass migration, failures in sanitation, poor building design, and a surge in vector populations contribute to turning the nation into a “crowded, germ-trading global market” (Scientific American, May 2018).
A number of cities, including Detroit and San Diego, have experienced severe epidemics of hepatitis A. Rates of hepatitis C have nearly tripled over the past 5 years.
About 19–21 million Americans are sickened with waterborne infections each year, estimates Kelly Reynolds of the University of Arizona School of Public Health, from taps, swimming pools, hot tubs, and showers. Many drinking-water distribution pipes are old; up to 20 percent of the water from the utility leaks out, and “where water leaks out, contaminants can leak in.” Energy-conservation measures that decrease water flow allow microbial biofilms to build up on pipe surfaces.
In Baltimore, some 65% of rats are infected with leptospirosis, which people and pets can catch from rat urine. Few cases are diagnosed because doctors don’t test for it.
“Neglected tropical diseases” are probably far more widespread than recognized in the U.S. The Centers for Disease Control and Prevention (CDC) estimates 300,000 cases of Chagas disease, with up to 45,000 cases resulting in heart failure each year, and 1,000 hospitalizations annually with neurocysticercosis, a brain tapeworm.
More than 300 people in a huge Hong Kong apartment complex came down with severe acute respiratory distress syndrome (SARS) after an infected visitor had diarrhea and flushed a toilet, because of the plumbing and ventilation arrangements. This accounted for 20% of cases in the 2002-2003 outbreak. If rooms are poorly ventilated, microbes in exhaled air or the stool droplets that permeate the air during a toilet flush become more concentrated over time. In 2016, University of Hong Kong researchers studying the dynamics of an influenza outbreak concluded that ventilation rate had a strong influence on the outbreak dynamics. “Opening a window, they noted, can reduce infection rate as much as getting vaccinated” (ibid.).
In 153 blocks of downtown San Francisco, including popular tourist spots, schools, and major hotels, the NBC Bay Area Investigative Unit found 41 blocks dotted with needles and 96 blocks sullied with piles of feces. The contamination is worse than in communities in Brazil, Kenya, or India, stated Dr. Lee Riley, an infectious disease expert at the University of California, Berkeley. He noted that feces becomes airborne when dry, and spreads infection (https://tinyurl.com/y7x77rgn).
Disease cases spread by insect vectors have tripled over the past 13 years in the U.S., with more than 640,000 cases reported between 2004 and 2016. These diseases include West Nile, dengue, chikungunya, Zika, and malaria (mosquito-borne); Lyme, ehrlichosis, babesiosis, and Rocky Mountain spotted fever (tick-borne); and bubonic plague (flea-borne), according to CDC (https://tinyurl.com/y8rrz2mr).
Malaria remains one of the world’s top killers. According to CDC, there were an estimated 216 million cases worldwide in 2016 and 445,000 deaths, mostly African children. About 1,700 cases of malaria are diagnosed in the U.S. each year.
While some expressed hope of a malaria-free southern Africa by 2018, cases tripled in 2017 (https://tinyurl.com/ya8jg6rt).
Climate change is accelerating the spread of vectors, according to Scientific American. A consortium of medical organizations, among other advocacy groups, claims that failure to limit CO2 emissions will “reverse 50 years of public health gains” (https://tinyurl.com/ycz7exq6, Climate Change IQ Question 10).
While speculative reports note the coincidence of increased disease incidence with warmer temperatures in recent decades, “climate has not consistently changed in the right way, at the right time, and in the right places to account for the recorded epidemiology of VBPs [vector-borne pathogens].” Trade, travel, land-use changes, poverty, and conflict are driving factors, while “climate change has played and will play a minor part (Lancet 12/1/12, https://tinyurl.com/yce2szho). A study of mosquito populations over the past century in North America showed almost no correlation with temperature. An up- to-tenfold increase in mosquito populations is correlated with increasing urbanization and with decreasing environmental concentrations of DDT. In NY, it took nearly 40 years for mosquito populations to reach pre-DDT levels (Nature Communications 2/16/16, tinyurl.com/y942jp3l).
Just after malaria deaths in Africa reached an all-time high in 1999, the campaign for an international ban on the world’s best anti-malaria tool, still being used with dramatic success in some areas (see tinyurl.com/ydyoh4z6), was joined by 260 environmental groups, including Physicians for Social Responsibility. For the amount of DDT once used on a cotton field, all the high-risk residents of a small country can be protected from malaria by indoor residual spraying (BMJ 12/2/2000, https://tinyurl.com/yd9nzl8n).
The main substitute for DDT, pyethroids (which are twice as expensive), in use since 1977, may be failing because of mosquito resistance. DDT and pyrethroids work by similar mechanisms, so mosquitoes may be resistant to both. Resistance to the immediate killing effects may not render DDT ineffective, as mosquitoes may still be repelled from entering houses. And their lifespan may be shortened, so malaria parasites may not have the needed 14 days to mature. Judicious use of pesticides—as by rotating the use of different chemical classes—is key. But political resistance to use of the least toxic pesticide—turning the Precautionary Principle upside down—has killed millions.
PLANETARY HEALTH
The “sustainable” Agenda 2020 touted by Politico misrepresents its own sources in blaming the spread of insect vectors on warming temperatures (tinyurl.com/yacxp45r). It calls for massive increases in “social spending,” comprehensive central planning, and a “post-carbon economy” (tinyurl.com/y9nb7mpz): things like “green, efficient buildings” (translated as “stack and pack” and cram into public transportation). Is “homelessness” the root cause of the hepatitis epidemic, because people can’t afford housing (NEJM 1/18/18)? How about social policy such as rent control that creates shortages, or expensive mandates such as California’s solar panel mandate, expected to add $8,000 to the cost of a new home? Where is the evidence measuring the outcome of human well-being?