Ebola screening at NZ airports – experts respond

Screening of at-risk passengers will begin at airports as part of increased efforts to prevent Ebola reaching New Zealand undetected, the Ministry of Health has announced.

Arrival card3The Ministry of Health website cautions:

“The risk of a traveller arriving in New Zealand with Ebola virus disease (EVD) remains very low.

“However, travellers arriving in New Zealand who in the last three weeks have visited West African countries affected by the Ebola viral disease outbreak will be screened for symptoms of the disease and where necessary receive a health assessment.”

The latest update from the World Health Organisation (WHO) estimates that, as of August 6, the cumulative number of cases of Ebola cases in Guinea, Liberia, Sierra Leone and Nigeria stands at 1779, including 961 deaths.

The SMC approached infectious disease experts for reaction to the announcement. Further comments will be posted as they are received.


Dr David Hayman, Senior Lecturer in Veterinary Public Health at the Molecular Epidemiology and Public Health Laboratory (mEpiLab), Massey University, responded to the following questions:

How does the spread of this virus compare to other well-known viruses?

“Ebola virus is not especially good at being transmitted among people, if you compare it to well-known viruses such as measles or influenza. However, clearly from the ongoing outbreak in West Africa, humans are not a dead-end host, like they are for other viruses with high case fatality rates, such as rabies, and transmission through close contact with cases can occur.”

What is different about this outbreak?

“The size of the outbreak is unique. It is uncertain if there is anything different about the viruses itself, though initial genetic studies suggest not. If the virus is similar to those in previous Zaire ebolavirus outbreaks, it suggests that a lack of control within a large, susceptible human population is the major reason for the outbreaks’ size.”

Can you elaborate on the connection to human disturbance of wildlife habitat — are animal-to-human viral outbreaks part of a larger trend?

“Viruses cannot appear out of nothing and require a host to survive. The evidence suggests Zaire ebolavirus circulates among forest-dwelling fruit bats, but to infect humans there must be an opportunity to go from those bats to humans. Increasing numbers of people encroaching into the forest habitats of bats will lead to increasing human and bat contact, even if indirect, and this is presumed to lead to an increase in viral emergence. This process appears to be an increasing global trend, even accounting for the better detection methods available today, suggesting reducing wildlife habitat disturbance could be good for wildlife and people.”

In your opinion, are the public at risk of overreacting to the threat the virus poses? Are there any misconceptions about how the virus spreads, or how deadly it is, that you would like to respond to?

“The risk to New Zealanders is likely to be extremely low. The virus currently requires close contact for transmission, which is why healthcare workers in West Africa have unfortunately been affected. If cases began to occur in countries with closer ties to W. Africa and New Zealand, such as in Britain, there may be greater risk to New Zealand. However, in nations with well-developed healthcare infrastructure it should be possible to contain the virus.

“Probably the greatest misconception regarding the virus is to do with the clinical signs of infection in people. From the case reports, it appears that the bleeding that gives the disease one of its names, Ebola hemorrhagic fever, it a bit of a misnomer and does not happen so frequently. However, bleeding can occur and the case fatality rates are very high with this Zaire ebolavirus strain of the virus. This high case fatality rate and severe disease is probably a major reason the virus has not previously spread too far globally though – because people die too quickly or are too sick to travel far.”

Any other points you would like to emphasise?

“One key issue that this outbreak highlights is the lack of healthcare infrastructure in countries such as those affected in West Africa. However, I believe it also highlights a need to better understand the processes that lead to infection emergence, whether that is hunting of bats and encroachment into forest, or some other mechanism. Many of these processes probably interact, so ongoing healthcare and infrastructure problems along with encroachment and hunting are all likely to contribute to outbreaks such as these. I believe it is necessary to understand these processes and try to prevent these outbreaks occurring in the future, preferably in ways that improve human and ecological health. If no improvements are made, there may well be other outbreaks of similar sizes, because nothing will have fundamentally changed in those countries.”


Prof John Crump, McKinlay Professor of Global Health and Co-Director Centre for International Health, University of Otago, responded to the following questions:

What is involved in screening for the Ebola virus at border checkpoints? What is the likelihood of detecting the virus this way? Is this just a precautionary measure?

“The New Zealand Passenger Arrival Card, completed by all people arriving in New Zealand overseas, includes a request to list all countries that they have been in during the past 30 days. This would serve as the primary method of identifying those who have travelled to affected areas. Fever is the most common initial symptom of ebola virus disease (EVD), but is also a feature of many infectious diseases that are far more common than EVD. The screening approach would detect possible cases of EVD disease among travellers who accurately report their travel history and who have symptomatic infection. It also affords the opportunity to provide EVD advice to well travellers from affected areas who might develop fever or other symptoms after arrival in New Zealand. New Zealand’s geographic isolation, lack of direct flights from west Africa, and limited travel volume from west Africa means that the risk of some one arriving in New Zealand with EVD is low, so the screening approach represents an abundance of caution.”

Would someone travelling to New Zealand from countries where the outbreak is taking place be likely to show overt symptoms by the time they arrived?

“Not necessarily. The incubation period for EVD is up to three weeks, so symptoms could develop after arrival. That is why information is being provided to apparently healthy travelers from affected areas as well.”

If Ebola did arrive in this country, what would the likely impact be?

“New Zealand hospitals are quite capable of instituting the infection control practices needed to protect healthcare workers and others from ebola infection. These practices are used routinely for other much more common, albeit less deadly, infections. The experience gained and measures in place to deal with other epidemic infectious diseases such as SARS Coronavirus and H1N1 influenza mean that health care facilities are prepared. The world has the advantage of knowing ebola since 1976, so we understand how it is transmitted. New Zealand has the advantage of having many months since the onset of the current outbreak to prepare.”

Why do people survive Ebola?

“Supportive care, that is, managing oxygen and breathing; fluids and electrolytes; and bacterial super-infections can substantially lower the case fatality ratio of EVD. The strain of the virus is also important. Ebolavirus Zaire appears to carry a higher case fatality ratio than Ebolavirus Sudan, for example. We don’t know as much as we would like to about patient factors that improve outcomes. Some patients clearly develop an immune response that ultimately clears the virus sometime during the second week of disease; supportive care aims to get get people the best chance by getting them through to when an effective immune response develops. While supportive care can improve survival, a large proportion of people with EVD will still die.”

How does the spread of this virus compare to other deadly viruses?

“Ebola is not transmitted by the airborne route. Instead it is transmitted by close contact with patients (both alive and dead), specifically contact with their body fluids (blood, vomit, saliva, sweat, semen, etc). By contrast other potentially fatal virus infections like measles and chicken pox are spread by the airborne route and you can become infected just by breathing the same air as the patient.”

In your opinion, are the public at risk of overreacting to the threat the virus poses? Are there any misconceptions about how the virus spreads, or how deadly it is, that you would like to respond to?

“Today 500 people will die of typhoid fever and 3,000 from malaria world wide and many more will be sickened. It is important that we keep EVD in perspective with other global infectious diseases problems. The concern is that the latest ebola outbreak has occurred in countries with recent histories of civil war, fragile health infrastructure, limited resources, weak organizational capability, poverty, and traditional beliefs and practices that may facilitate spread and make control more challenging. It is essential that the global community support Guinea, Sierra Leone, and Liberia with the resources, personnel, and expertise needed to control the outbreak to prevent more deaths and wider regional spread. Our concern should first be for the citizens of those countries affected and for those trying to help. The risk to us is quite remote.”

Any other points you would like to emphasise?

“Work has been done to design vaccines and treatments for EVD. However, since EVD has occurred in small outbreaks of short duration, it has been difficult to take these products through the phases of studies needed to confirm safety and efficacy, which often take years.”