The Maritime Declaration of Health (MDH) as a tool to detect maritime traffic-related health risks: analysis of MDH forms submitted to Spanish ports, October 2014 to March 2015

The international maritime traffic of people and goods has often contributed to the spread of pathogens affecting public health. The Maritime Declaration of Health (MDH), according to the International Health Regulations (IHR) (2005), is a document containing data related to the state of health on board a ship during passage and on arrival at port. It is a useful tool for early detection of public health risks. The main objective of our study was to evaluate compliance with the model provided in the IHR, focusing on the format and degree of completion of MDH forms received at Spanish ports. We reviewed the content of 802 MDH forms submitted to nine Spanish ports between October 2014 and March 2015. Study results show that 22% of MDH forms presented did not comply with the recommended model and 39% were incomplete. The proportion of cargo ships with correct and complete MDH forms was lower than passenger ships; thus, the nine health questions were answered less frequently by cargo ships than passenger ships (63% vs 90%, p value < 0.001). The appropriate demand and usage of MDH forms by competent authorities should improve the quality of the document as a tool and improve risk assessment.


Introduction
In today's interdependent and interconnected world, it is possible for diseases to spread rapidly across the world and threaten public health. This is possible because of highly mobile human populations, international transport and trade. International public health security depends on the appropriate management of public health risks, which in turn depend on national capacities and international collaboration [1,2]. Effective public health measures and response capacities at airports, ports and ground crossings worldwide reduce the risk of the international spread of disease [3][4][5].
The International Health Regulations (IHR) (2005) [6] is a key international public health document that is legally binding across 196 countries, including all World Health Organization (WHO) Member States, requiring them to work together for global health security. This fundamental document requires that ratifying countries have the ability to detect, assess, report and respond to public health events [7,8].
The IHR (2005) includes provisions for the use of various health documents that can be presented, if requested, to health authorities on arrival at ports and airports [9]: the Ship Sanitation Certificate (Annex 3), the International Certificate of Vaccination and Prophylaxis (Annex 6), the Maritime Declaration of Health (MDH) (Annex 8) and the Health Part of the Aircraft General Declaration (Annex 9). If these documents are used inappropriately, it may result in an inadequate assessment of public health issues related to international traffic. There is also an IHR List of Authorized Ports to Issue Ship Sanitation Certificates, published and updated by the WHO, that lists all ports each state party has authorised to issue Ship Sanitation Certificates [10]. According to Article 37 of the IHR (2005) [6], 'the master of a ship, before arrival at its first port of call in the territory of a State Party, shall ascertain the state of health on board, and, except when that State Party does not require it, the master shall, on arrival, or in advance of the vessel's arrival if the vessel is so equipped and the State Party requires such advance delivery, complete and deliver to the competent authority for that port a Maritime Declaration of Health which shall be countersigned by the ship's surgeon, if one is carried'. The state party may decide whether it requires all arriving ships to submit a MDH, which should conform to the model provided in Annex 8 of the IHR [6]. For European Union (EU) countries, according to Directive 2010/65/EU, the MDH is one of the forms that must be submitted to the first European port of arrival [11]. The EU SHIPSAN ACT Information System (SIS), developed within the scope of the EU SHIPSAN ACT Joint Action [12], allows port health authorities to confidentially share completed MDH forms between EU ports. Seamless and close communication between the master and port health authorities via the MDH enables the latter to detect onboard health problems that might constitute a risk to public health at an early stage and to take immediate measures to reduce the risk of onward transmission [13]. Therefore, it is essential that a MDH form is completed correctly at the onset of the assessment [13].
The International Maritime Organization (IMO) is a specialised agency of the United Nations that is responsible for measures to improve the safety and security of international shipping, and to prevent pollution from ships. One of its conventions, the Convention on Facilitation of International Maritime Traffic (FAL Convention), aims to facilitate maritime transport by simplifying and minimising formalities, data requirements and procedures associated with the arrival, stay and departure of ships engaged in international voyage [14]. The FAL Convention's main objectives are to 'prevent unnecessary delays in maritime traffic, to aid co-operation between Governments, and to secure the highest practicable degree of uniformity in formalities and other procedures. In particular, the Convention reduces the number of declarations which can be required by public authorities' [14]. At present, according to FAL Convention, ships may be required to complete nine documents: seven IMO-standardised forms (the General Declaration, Cargo Declaration, Ship's Stores Declaration, Crew's Effects Declaration, Crew List, Passenger List and Dangerous Goods Declaration), one Universal Postal Convention document and one International Health Regulations document (the MDH). Health authorities do not systematically inspect all ships, however, they review all the MDH presented.
Spain's geographical position, and the fact that it is a peninsula with 8,000 km of coastline with access to the Mediterranean Sea and the Atlantic Ocean, favour the frequent passage of ships [15]. As of 2016, Spain had 33 ports authorised to issue Ship Sanitation Certificates under the IHR [10]. All of these have medical inspectors (port health authorities) to evaluate events that suggest health risks on ships. For these reasons, and because there are numerous ports with high volumes of maritime traffic, cargo and passengers, Spain was considered ideal in terms of studying the quality of MDH forms. The aim of this study was to examine current MDH practice, as there are no previous studies on this issue, in order to enable health authorities to improve their capacity to detect and respond to health problems on board ships. For this purpose, we were mainly interested in evaluating whether the MDH forms used by ships conformed to the model set out in Annex 8 of IHR (2005), the extent of the form's completion by ships, and whether there were differences in completion and content depending on the type of ship or the geographical area of the port.

Study design
This was a descriptive study of MDH forms presented to Spanish ports by ships from all shipping routes. The object of analysis was the MDH form submitted by each ship to port authorities. The study analysed and compared MDH forms from different types of ships, as well as different MDH types.

Sample size
We calculated the representative sample size using the following information: in 2014 ca 140,000 ships arrived at Spanish ports [15]. First, we studied MDH forms presented to port authorities over a 6-month period, from October 2014 to March 2015. Then, based on an estimated population of 70,000 ships over a 6-month period, with a 99% confidence level and a 5% margin of error, the calculated minimum sample size was 569 MDH forms.

Participating ports
Nine of Spain's 33 IHR-authorised ports participated in this study: A Coruña, Santander and Vigo (Atlantic Ocean ports on the northern coast); Algeciras, Santa Cruz de Tenerife and Huelva (Atlantic Ocean ports on the southern coasts and Canary Islands); and Barcelona, Malaga and Tarragona (Mediterranean Sea ports). They were selected based on geography (to obtain information on the different shipping routes) and their inclusion on the IHR list of ports authorised to issue Ship Sanitation Certificates at the time of the study [10]. We requested 100 consecutive MDH forms from each port from October 2014 onwards in the order in which they were presented at the port. To avoid inter-observer bias, all MDH forms were reviewed by a single observer. Any uncertainty of the single observer was resolved by the first four authors of the study via a specific procedure.

Questionnaire to study MDH forms
Data were entered and analysed using SPSS 15.0. We undertook descriptive statistics for each variable in the questionnaire. For those variables that could influence the distribution (e.g. type of ship, geographical area of the port and type of MDH (positive or negative), we used a chi-squared test to study the possible differences in the filling out of the questions on the MDH form in terms of completion and correctness. We studied the measures of association for nominal data: Pearson's contingency coefficient C, Cramer's V coefficient and phi coefficient. A value of p < 0.05 was considered statistically significant.

Results
We analysed a total of 802 MDH forms submitted to nine selected ports. The ports and geographical areas where the MDH forms were submitted are shown in Table 1. Regarding these forms, 57% (n = 347) were submitted by passenger ships and 43% (n = 455) by cargo ships. Table 2 shows the proportion of each document field that was properly (completely and correctly filled), and the differences between cargo and passenger ships. We found that the nine health questions were properly answered in just 75% (n = 601) of the submitted MDH forms. The question asking whether the ship had visited an affected area was unanswered in 29% of MDH forms. In addition, 15% of the forms were not signed by the ship's master, which is required according to Article 37 of the IHR. Some variables, including ship type, geographical area of the port, and type of MDH, were studied regarding the degree of completion of the document and validity. We found statistically significant associations between the type of ship 'passenger' and the following variables: (i) greater probability that the items of the MDH will be complete ( Table 2); (ii) the MDH model is consistent with Annex 8 of the IHR (2005) ( Table 3); (iii) the Ship Sanitation Certificate was issued by an authorised port (Table 3); and (iv) the Ship Sanitation Certificate was issued less or equal than 6 months before date of MDH) ( Table 3). The comparison of positive MDHs between cargo and passenger ships could not be carried out because of the low number of positive MDHs from cargo ships. Only five of the analysed variables showed significant differences when positive and negative MDH forms were compared:
• Invalid Ship Sanitation Certificates because more than 6 months between date of issue and date on the MDH form: 3% (3/91) of positive MDH forms and 12% (83/711) of negative forms (p = 0.015).
When comparing the MDH variables between different geographical areas we found some statistically significant differences. However, these differences disappear if the variable 'type of ship' is introduced in the analysis. Cargo ships are most frequently in the ports on the Atlantic Ocean coast (64% cargo ships vs 36% passenger ships) and passenger ships are most frequently in the ports on the Mediterranean Sea coast (55% passenger vs 45% cargo) (p < 0.001).

Discussion
There are a few studies to date that analyse compliance with the IHR (2005) recommendations and the use of related documents. In 2011, Hadjichristodoulou et al. [9] reported that the MDH was the main reporting tool used for the surveillance and monitoring of communicable diseases on passenger ships in Europe. However, only 30% of the 59 competent authorities surveyed reported that they require all arriving ships to submit MDH forms. In special situations of health surveillance, as in during the early stages of pandemic influenza A in 2009, Schlaich et al. [16] showed that 32% of shipping companies experienced one or more health screening measures by port health authorities. Furthermore, a request to complete the MDH form was reported by 23% of the companies that participated in the study (7/31).  [20]. An incomplete MDH makes it difficult to assess risks and requires additional communication with the ship to obtain the missing information. Such omissions lengthen the response time, and reduce the effectiveness and efficiency of monitoring. This highlights the importance of fully completing the MDH form for the early detection of events and for timely implementation of public health measures on board ships, as per the WHO requirements [3].
Cargo ships require greater attention by the port health authorities as our study shows that their MDH forms are more frequently incomplete. Unlike passenger ships, freighters often lack medical services, make longer journeys and use multiple shipping routes, which can hinder the management of diseases.
Usually, when a correct and complete MDH informs the port health authorities of communicable diseases or other potential public health problems, competent authorities assess the information, confirm the situation on board and propose appropriate measures for each situation, such as isolation, landing, disinfestation, decontamination and vaccination.
It should be considered as a limitation that this study was unable to determine if all ships with potential health risks on board recorded this information on a MDH form because health authorities do not systematically inspect all ships. In addition, given that descriptive studies often represent the first scientific dip into new areas of inquiry, the limitations of this study must be addressed in subsequent analytical studies [21]. Further studies are required to assess whether the MDH is, in practice, a reliable reporting tool. For this, it would be necessary to inspect all ships arriving at ports, interview masters or doctors on board, and check whether the information recorded on MDH forms represents the reality on board; however, this is not a feasible goal.

Conclusions and recommendations
The MDH document brings together information to assess the state of health on board a ship. Its proper completion is key to conducting a preliminary risk assessment, and efforts should be made to achieve this goal. Thus, masters and specific crew members should be properly trained to complete the MDH in such a way that port health authorities can assess the situation in advance.
We believe that an improvement in the current use of the MDH will result in improved risk assessment, greater confidence in the information provided and improve the trust between ships, health authorities and other stakeholders in the port, such as conveyance operators, relevant port authorities and surveillance system operators. Monitoring the implementation of the IHR (2005) guidelines related to the MDH should not only include monitoring the use of appropriate communication channels, but also an evaluation of the quality of the information provided. In later phases, the proper use of the MDH should be assessed and measured to prevent and provide a public health response to the international spread of disease.
Several countries might be involved in the response to an outbreak on board a ship. Therefore, the MDH should not be considered an isolated document concerning only one country, but a source of information that should be shared between port health authorities for follow-up action. The use of the SIS, a tool developed by the EU SHIPSAN project for the immediate sharing of information between ports, should be encouraged for the transmission of such information. Further, training masters on the importance of the MDH and how to routinely use it would also help facilitate prompt responses in the case of a complex public health event occurring on their ships.
Finally, further studies should be conducted to assess the real value of the MDH as a public health assessment tool for events on ships. One such avenue could be the analysis of the consequences to public health when the MDH is not properly completed.
expertise, and also has made a substantial contribution to final revision.