Who’s Got What Aboard Your Plane?
Like it or not, the quickest way to catch a deadly disease or infection is to be admitted to hospital. That’s a statistical fact. But it’s now looking like the next best way to become seriously ill is to travel regularly by air. It used to be the second-hand smoke that was just an unsociable annoyance, but that was cured on 99 percent of airlines by banning smoking. Then along came SARS and Ebola with H5N1 variants of bird flu now “waiting in the wings” (so to speak). However now there’s a new threat in the wind and it’s quite deadly. On 29 May the Center for Disease Control and Prevention (CDC) started an urgent search for passengers who’d been exposed to a US citizen who’d recently traveled on two international flights. That passenger was infected with an extensively drug-resistant form of tuberculosis known as XDR-TB. This variant of TB was recently defined as a subtype of multiple-drug resistant tuberculosis. It’s more often (than not) fatal. It used to be that you could be inoculated against most virulent diseases likely to be encountered whilst abroad. Unfortunately there’s no protection against TB.
As with all forms of TB, the disease can be spread through the air. Aircraft cabin air can be (and usually is) recirculated. The filtration system isn’t micropore and doesn’t filter out all microbes, although Boeing claims that between 94 and 99.9 percent of the airborne microbes are captured. Supposedly many aircraft are equipped with air filters that are designed to trap the long, rod-shaped tuberculosis bacilli. HEPA (High Efficiency Particulate Air) filters are the highest efficiency air filters available for the filtration of small particles. Defined by the Institute of Environmental Science, a Certified HEPA filter must capture a minimum of 99.97% of contaminants at 0.3 microns in size – but many germs and spores are smaller than that. There’s no guarantee of immunity for other passengers not in close proximity. Recirc cabin air is a very effective distribution mechanism for respiratory diseases and can cover subsequent flights. At least 17 percent of TB cases are transmitted by carriers. A CDC agency spokesman said. “In this case, the infected patient traveled on two trans-Atlantic flights and may have exposed passengers and crew to XDR-TB.” To emphasize the critical urgency of the case and to curtail a possible epidemic, a federal quarantine order has now been issued and the CDC is currently collaborating with U.S., state and local health departments, international ministries of health, the airline industry, and WHO (World Health Organization).
Dr. Julie Gerberding, head of the CDC, says the person traveled on Air France Flight 385 (Atlanta to Paris) on May 12 and Czech Air flight 0104 (Prague to Montreal) on May 24 in order to elude authorities searching for him. He entered the United States by car. “We have no suspicion that this patient was highly infectious, in fact the medical evidence would suggest that his potential for transmission would be on the low side, but we know it isn’t zero,” Gerberding said. However, it is the first such quarantine order to be issued in more than 44 years. The last order was issued in 1963, to quarantine a patient with smallpox. In addition, the case easily meets WHO guidelines for initiating a global airline contact investigation. CDC officials arranged for the patient to be flown Monday from New York to his hometown Atlanta aboard a specially equipped CDC plane. In Atlanta, he was issued a federal isolation order that compulsorily placed him in the care of State Health Officers.
The man was aware of his diagnosis at the time of the flights, but may not have known that he had a highly drug-resistant form of the disease. The WHO page covering this untreatable form of tuberculosis is at tinyurl.com/k2caf. The XDR stands for Extreme Drug Resistant.
A recent outbreak of XDR-TB in an HIV-positive population in Kwazulu-Natal in South Africa was characterized by alarmingly high mortality rates. Of the 544 patients studied, 221 had Medium DR-TB. Of those 221 cases, 53 were redefined as XDR-TB. Of the 53 patients, 44 had been tested for HIV and all were HIV-positive. 52 of the 53 patients died, on average, within 25 days. Between 1993 and 2006, XDR-TB was diagnosed in 49 people in the United States, said Dr. Ken Castro, director of the division of TB Elimination at CDC. But the disease is more common elsewhere, he said. “When they looked, they found it in every single continent of the world,” he said.
By comparison, the SARS mortality rate is only 20 percent. Amongst the notifiable diseases (see BOX1) XDR-TB is by far the most prevalent, contagious and therefore worrisome. Crew and fellow passengers seated in the same row or two rows ahead of (or behind) the patient aboard either flight must be evaluated for TB infection. “This includes evaluation and testing with follow-up pulmonary screening eight to 10 weeks later for confirmation,” the CDC said. But the CDC also acknowledged that they are not sure just who is at risk, and recommended that everyone aboard the flights be tested. They dare not consider who may have been exposed more generally within terminal areas. WHO estimates that there were almost half a million cases of multiple-drug-resistant tuberculosis worldwide in 2004.
Note that a captain may reject a passenger who is coughing or showing signs of pulmonary infection, but that is likely only when (or if) another passenger complains. This happened on a Honolulu-bound Newark 767-400 flight in early March, despite a doctor onboard certifying that the woman, Rachel Collier, was fit to fly. Once it had been brought to his attention, the Continental captain (and his airline) would have been liable if any passenger(s) had contracted a communicable disease. MedLink (see medaire.com) is an inflight advisory service for crews covering situations arising whilst airborne – not at boarding. The moral would seem to be not to have a coughing fit whilst boarding, or the decision is likely to be not to board you.
According to Dr. Claus Curdt-Christiansen of the International Civil Aviation Organization (ICAO), TB is “one of the most vexing aeromedical problems of modern air transportation. Within the next decade we can expect more than two billion passengers per year in scheduled air traffic alone,” he said. “Long-haul flights combined with the confined space of a passenger cabin and the close proximity to co-passengers from the entire world facilitates the spread of contagious diseases. In-flight exposure to infectious tuberculosis in co-passengers has become a realistic airline possibility owing to the high prevalence of tuberculosis in some regions of the world.” WHO recommends that “maximum efficiency air filters should be installed and properly maintained on all aircraft and ground delays kept to a minimum. Anyone with infectious TB should postpone travel until they become non-infectious. Boarding can and should be denied to persons with infectious TB.”
So far, because of the incubation period, no case of TB has been proven to have been contracted aboard an aircraft. However if a number of passengers were proven to have traveled aboard an aircraft with a passenger that was later found to have had the infectious stage of TB, it’s unlikely that the airline would be able to weasel out of liability with the same ease with which they adroitly evaded responsibility for DVT (Deep Vein Thrombosis). With the increased reporting levels for TB, it’s only a matter of time before that litigious minefield is broached.
Meanwhile, also on 29 May, Canadian health officials have quarantined around 130 Japanese tourists in the southwestern Rocky Mountain resort town of Banff after one sick member of the group tested positive for measles. Health officials in Vancouver are trying to reach all passengers that were on board the tourist group’s flight from Japan to Vancouver, as well as anyone else who may have been exposed to the group members. Hundreds of students have been infected by measles in Japan, forcing the closure of about a dozen universities for varying periods. The outbreak is believed to be Japan’s largest in the past five years.
Cabin release of airborne viruses or aerosol poisons, whether intentional or not, has always been a post-911 concern. Researchers at Purdue University in the US have written a computer program that can backtrack to the air release point of biological pathogens. An outline of the Purdue program is at tinyurl.com/342zmh. After a cabin contamination, scattered sensors track the airflow pattern and collect data related to factors such as temperature, velocity and concentration of gases and particles in the air. It is equally effective for tracing bacteriological agents as diverse as anthrax or TB spores or pandemic flu released via a sneeze. Sensors installed inside an airliner’s cabin are able to detect the presence of biological agents (germs) and, via a series of mathematical models, back-trace the dispersion path to origin. Extensive testing of the theory has led to a verified concept of inverse simulation, a process of reverse engineering. Input data includes aircraft design airflow patterns, bio-concentrations and ambient temperature. The algorithms are presently computer time intensive and can take several days to reach a determination. However Purdue researchers are looking to reduce that to one day and also intend to hone the system such that it can instantly detect the release of a biological agent. In an A380, the program may be invaluable for narrowing down both victims and terrorists/carriers, albeit at some stage after disembarkation of around 600+ passengers. The Purdue research is funded primarily by the FAA’s Office of Aerospace Medicine, but the Transport Security Administration also has a vested interest. Whether or not the technology is adopted may depend on whether security experts deem it easier to stop lethal agents being boarded as aerosols. However the ultimate aerosol container is a martyr infected with an aerosol deployable agent. Being a martyr, the terrorist wouldn’t need to have the personal invulnerability of a Typhoid Mary.
These communicable diseases are covered by the Public Health Service Act which mandates a quarantine:
(a) Cholera; Diphtheria; infectious Tuberculosis; Plague; Smallpox; Yellow Fever; and Viral Hemorrhagic Fevers (Lassa, Marburg, Ebola, Crimean-Congo, South American, and others not yet isolated or named).
(b) Severe Acute Respiratory Syndrome (SARS) is a disease associated with fever and signs and symptoms of pneumonia or other respiratory illness, and is transmitted from person to person predominantly by the aerosolized or droplet route.
(EXECUTIVE ORDER 13295)